顔写真

イトウ タカシ
伊藤 隆
Takashi Itoh
所属
高等研究機構学際科学フロンティア研究所 先端学際基幹研究部 物質材料・エネルギー研究領域
職名
准教授
学位
  • 博士(工学)(東北大学)

  • 修士(工学)(石巻専修大学)

委員歴 20

  • 一般社団法人表面技術協会 評議員

    2018年4月 ~ 継続中

  • 公益社団法人 電気化学会 東北支部 事務幹事

    2014年4月 ~ 継続中

  • 公益社団法人 電気化学会 ナノ界面・表面研究懇談会 常任理事

    2007年2月 ~ 継続中

  • 社団法人 表面技術協会 東北支部幹事

    2003年4月 ~ 継続中

  • ナノ界面・表面研究懇談会 東北支部幹事

    2000年4月 ~ 継続中

  • 公益社団法人 電気化学会 広報委員会 委員

    2022年4月 ~ 2024年3月

  • 公益社団法人 電気化学会 大会学術企画委員会 委員

    2022年4月 ~ 2024年3月

  • 公益社団法人 電気化学会 大会改革タスクフォース 委員

    2023年8月 ~ 2023年12月

  • 公益社団法人 電気化学会 2022 年電気化学秋季大会実行委員会 委員

    2022年6月 ~ 2022年9月

  • 公益社団法人 電気化学会 産学官フォーラム運営委員会 運営委員

    2015年3月 ~ 2017年3月

  • 公益社団法人 電気化学会 理事

    2014年3月 ~ 2016年3月

  • 公益社団法人電気化学会 大会学術企画委員

    2011年3月 ~ 2013年2月

  • 社団法人 表面技術協会 評議員

    2007年2月 ~ 2011年1月

  • 公益社団法人 電気化学会 電池技術委員会 ゲストエディター

    2009年11月 ~ 2010年2月

  • 日本化学会 東北支部 会計監査

    2009年3月 ~ 2010年2月

  • 公益社団法人 電気化学会 電気化学会誌 編集委員

    2006年2月 ~ 2010年2月

  • 日本化学会 東北支部 幹事長

    2008年2月 ~ 2009年2月

  • 公益社団法人 電気化学会 評議員

    2006年2月 ~ 2008年2月

  • 日本化学会 東北支部 地方大会 プログラム編成委員

    2005年7月 ~

  • 日本化学会 東北支部 地方大会 プログラム編成委員

    2004年7月 ~

︎全件表示 ︎最初の5件までを表示

所属学協会 6

  • 表面科学会

  • 表面技術協会

  • アメリカ電気化学会

  • アメリカ化学会

  • 電気化学会

  • 日本化学会

︎全件表示 ︎最初の5件までを表示

研究分野 1

  • ナノテク・材料 / 基礎物理化学 / 表面科学

受賞 5

  1. Asia Pacific Society for Materials Research 2019 Annual Meeting

    2019年7月 Asia Pacific Society for Materials Research In Situ Raman Analysis for High Capacity Zinc Anode in Alkaline Solutions

  2. 日本表面科学会 論文賞

    2011年12月15日 公益社団法人 日本表面科学会

  3. インテリジェント・コスモス奨励賞

    2007年5月16日 財団法人インテリジェント・コスモス学術振興財団

  4. 電気化学会 電池技術委員会賞

    2003年11月5日 電気化学会 電池技術委員会 その場ラマン散乱分光法によるリチウムマンガンスピネルの解析

  5. 電気化学会 進歩賞・佐野賞

    2003年4月2日 電気化学会 エネルギー変換デバイスのその場ラマン分光と電気化学測定に関する研究

論文 147

  1. Enhanced Photoanodic Activity and Outermost Surface Crystallinity of Tungsten Oxide via High-temperature Sintering 査読有り

    Toshiyuki Abe, Hideya Tsuchikado, Mitsuharu Chisaka, Takashi Itoh, Guoqing Guan, Abuliti Abudula

    Electrocatalysis 15 (1) 120-127 2023年12月20日

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1007/s12678-023-00859-2  

    ISSN:1868-2529

    eISSN:1868-5994

  2. Synthesis and Characterization of Ionic Li+@C70 Endohedral Fullerene 査読有り

    Hiroshi Ueno, Daiki Kitabatake, Takuya Mabuchi, Shinobu Aoyagi, Takashi Itoh, Ting Deng, Fuminori Misaizu

    Chemistry – A European Journal 2023年11月30日

    出版者・発行元:Wiley

    DOI: 10.1002/chem.202303908  

    ISSN:0947-6539

    eISSN:1521-3765

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    Ion‐endohedral‐fullerene has attracted growing interest due to the unique electronic and structural characteristics arising from its distinctive ionic nature. Although there has been only one reported ion‐encapsulated fullerene, Li+@C60, a significant number of fundamental and applied studies have been conducted, making a substantial impact not only in chemistry and physics but also across various interdisciplinary research fields. Nevertheless, studies on ion‐endohedral fullerenes are still in their infancy due to the limitations in variety, and hence, it remains an open question how the size and symmetry of fullerene, as well as the motion and position of the encapsulated ion, affect their physical/chemical properties. Herein, we report the synthesis of lithium‐ion‐endohedral [70]fullerene (Li+@C70 X−, X=PF6− and TFSI−), a novel ionic endohedral fullerene. X‐ray crystallography confirmed the encapsulation of Li+ by C70 cage as well as its ion‐pair structure stabilized by external TFSI− counter anion. The encapsulated Li+ drastically lowered the orbital energy of the C70 cage by Coulomb interactions but did not affect the orbital energy gap and degeneracy. DFT studies were also performed, which supported the experimentally observed electronic effects caused by the encapsulated Li+.

  3. Controlled Solvation Structure of a Zn Ion in an Aqueous Electrolyte by Amine Additives for Long Cycle Life of a Large Capacity Zn-Air Rechargeable Battery 査読有り

    Tatsumi Ishihara, Yuiko Inoishi, Sun Kim, Aleksandar Staykov, Motonori Watanabe, Nao Naohara, Kimiko Takahashi, Takashi Itoh

    The Journal of Physical Chemistry C 127 (14) 6619-6628 2023年4月4日

    出版者・発行元:American Chemical Society (ACS)

    DOI: 10.1021/acs.jpcc.2c08682  

    ISSN:1932-7447

    eISSN:1932-7455

  4. One-pot multi-step synthesis of high-aspect-ratio Cu nanowires based on an environment-friendly manner for low-cost and high-performance transparent conductive films 査読有り

    Yuta Umemoto, Shun Yokoyama, Kenichi Motomiya, Takashi Itoh

    Colloids and Surfaces A: Physicochemical and Engineering Aspects 651 129692-129692 2022年10月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.colsurfa.2022.129692  

    ISSN:0927-7757

  5. Highly crystalline graphite-like carbon from wood via low-temperature catalytic graphitization 査読有り

    Yuta Nakayasu, Yasuto Goto, Yuto Katsuyama, Takashi Itoh, Masaru Watanabe

    Carbon Trends 8 2022年7月

    DOI: 10.1016/j.cartre.2022.100190  

    eISSN:2667-0569

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    In this study, we investigated the synthesis of wood-sawdust-derived high-crystalline graphite-like carbon. The sawdust was first impregnated with Fe and semi-carbonized by a hydrothermal treatment (HT) at 250°C, followed by the second carbonization under N2 atmosphere and acid washing. For an iron-to-sawdust weight ratio of 4:10, graphite-like carbon was synthesized at a very low temperature of 850°C. This carbon has an average interlayer distance and crystallite size (d002: 0.337 nm, La: 35.8 nm, and Lc: 56.1 nm) comparable to those of commercial graphite. The large size of the Fe crystal particles facilitates the development of a stacked structure of carbon sheets. The HT with Fe-impregnated sawdust generates larger iron oxide particles than simple semi-carbonization with Fe-impregnated sawdust under N2 atmosphere at 250°C, facilitating the development of more crystalline graphite-like carbon. It was also found that the crystallinity of the graphitic carbon obtained after second carbonization may be controlled by the amount and particle size of the added Fe.

  6. Synthesis of unused-wood-derived C-Fe-N catalysts for oxygen reduction reaction by heteroatom doping during hydrothermal carbonization and subsequent carbonization in nitrogen atmosphere 査読有り

    Yasuto Goto, Yuta Nakayasu, Hiroya Abe, Yuto Katsuyama, Takashi Itoh, Masaru Watanabe

    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379 (2209) 2021年11月1日

    DOI: 10.1098/rsta.2020.0348  

    ISSN:1364-503X

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    There is an urgent need to develop renewable sources of energy and use existing resources in an efficient manner. In this study, in order to improve the utilization of unused biomass and develop green processes and sustainable technologies for energy production and storage, unused Douglas fir sawdust (SD) was transformed into catalysts for the oxygen reduction reaction. Fe and N were doped into SD during hydrothermal carbonization, and the N- and Fe-doped wood-derived carbon (Fe/N/SD) was carbonized in a nitrogen atmosphere. After the catalyst had been calcined at 800°C, its showed the highest current density (-5.86 mAcm -2 at 0.5 V versus reversible hydrogen electrode or RHE) and E onset value (0.913 V versus RHE). Furthermore, its current density was higher than that of Pt/C (20 wt% Pt) (-5.66 mA cm -2 @0.5 V versus RHE). Finally, after 50 000 s, the current density of sample Fe/N/SD (2: 10: 10) remained at 79.3% of the initial value. Thus, the synthesized catalysts, which can be produced readily at a low cost, are suitable for use in various types of energy generation and storage devices, such as fuel cells and air batteries. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

  7. Flexible and adhesive sintered Cu nanomaterials on polyimide substrates prepared by combining Cu nanoparticles and nanowires with polyvinylpyrrolidone 査読有り

    Shun Yokoyama, Junpei Nozaki, Yuta Umemoto, Kenichi Motomiya, Takashi Itoh, Hideyuki Takahashi

    Colloids and Surfaces A: Physicochemical and Engineering Aspects 625 126907-126907 2021年9月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.colsurfa.2021.126907  

    ISSN:0927-7757

  8. Control of galvanic replacement reaction between Cu nanowires and Ag species under vacuum filtration for transparent conductive films with long-term durability 査読有り

    Shun Yokoyama, Yuta Umemoto, Kenichi Motomiya, Takashi Itoh, Hideyuki Takahashi

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 611 2021年2月

    出版者・発行元:ELSEVIER

    DOI: 10.1016/j.colsurfa.2020.125809  

    ISSN:0927-7757

    eISSN:1873-4359

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    Ag coatings on Cu nanowire (NW) surfaces are widely studied for making durable transparent conductive films. Although the galvanic replacement reactions (GRRs) between Cu NWs and Ag species were usually employed, non-uniform Ag layers were obtained due to their rapid reaction rates, leading to non-durable films. Herein, the GRR between Cu NW surfaces and Ag complexes in citric acid solutions was controlled by vacuum filtration, obtaining uniform Ag-coated NWs for durable films. Citric acid removed the surface impurities from the Cu NW surfaces and also modified the surfaces. While adsorbed to the NWs, citric acid delayed the Cu dissolution in aqueous solution, enabling regulation of the Ag concentration, solution volume, and temperature of the GRR. The GRR was precisely controlled by lowering some or all of these three factors under vacuum filtration. In the controlled reactions, the slow reaction rates caused partial Ag crystal growth on the surfaces. The heterogeneity of the growth increased with solution volume, producing large surface irregularities. At fast reaction rates with high Ag concentrations, the Ag species uniformly reacted with the Cu NW surface within a short time, leading to Cu NWs with fewer surface irregularities and thicker Ag layers than at slow reaction rates. After the GRR, the sheet resistance of the Cu NWs was lowered because the Ag crystal growth between the Cu junctions decreased the contact resistance. In transparent Cu NW films with a thick Ag layer, the sheet resistance was retained for 300 h at high-temperature (130 degrees C) and under standard harsh conditions (85 degrees C and 85% relative humidity).

  9. Functionalization of primary amine groups to single-walled carbon nanotubes by reacting fluorinated SWCNTs with ammonia gas at a low temperature 査読有り

    Koji Yokoyama, Yoshinori Sato, Masashi Yamamoto, Tetsuo Nishida, Takashi Itoh, Kenichi Motomiya, Yoshinori Sato

    Carbon 172 360-371 2021年2月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.carbon.2020.10.038  

    ISSN:0008-6223

  10. Spectroscopic Analysis of Rechargeable Lithium-Ion Battery Electrolyte Solution by a Compact FTIR System located in a Glovebox 招待有り 査読有り

    FTIR TALK LETTER 35 2-5 2021年1月

  11. グローブボックス中に設置した小型FTIRによるリチウム2次電池電解液の分光解析 招待有り 査読有り

    伊藤 隆

    FTIR TALK LETTER 35 2-5 2020年

  12. 電気化学反応のその場ラマン分光法 招待有り 査読有り

    伊藤隆

    87 (Spring) 43-56 2019年3月5日

    出版者・発行元:None

    DOI: 10.5796/denkikagaku.19-te0001  

    ISSN:2433-3255

    eISSN:2433-3263

  13. Electrochemical capacitors using nitrogen-doped vertically aligned multi-walled carbon nanotube electrodes prepared by defluorination 査読有り

    Rei Nonomura, Takashi Itoh, Yoshinori Sato, Koji Yokoyama, Masashi Yamamoto, Tetsuo Nishida, Kenichi Motomiya, Kazuyuki Tohji, Yoshinori Sato

    Carbon 132 539-547 2018年6月1日

    出版者・発行元:Elsevier Ltd

    DOI: 10.1016/j.carbon.2018.02.071  

    ISSN:0008-6223

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    Nitrogen-doped vertically aligned multi-walled carbon nanotubes (N-VAMWCNTs) were prepared by reacting fluorinated VAMWCNTs with ammonia gas at temperatures of 300–600 °C. The N-VAMWCNTs were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman scattering spectroscopy. In addition, the electrochemical properties of capacitors with N-VAMWCNT electrodes were evaluated by cyclic voltammetry and AC impedance spectroscopy using a two-electrode coin-type cell in an electrolyte of propylene carbonate containing triethylmethylammonium tetrafluoroborate. All the samples were prepared without destroying the alignment structure of the nanotubes. The ratios between the concentration of fluorine, carbon, and nitrogen (F/C and N/F) and the R value (degree of crystallinity) of the samples indicate that the N-VAMWCNTs prepared at 500 °C (N500-VAMWCNTs) had the highest level of nitrogen doping and the best crystallinity among the samples. Nitrogen atoms were doped at a concentration of 5.26 at% into the nanotube frames, thus enriching the N500-VAMWCNTs with pyridinic nitrogen species. The average specific capacitance of the N500-VAMWCNT electrodes was 12.0 F/g at a scan rate of 100 mV/s, which is approximately 1.8 times the value obtained for the as-grown VAMWCNT electrodes (6.5 F/g).

  14. Mixed ether-based solvents provide a long cycle life with high rate capability to graphite anodes for Na-ion batteries 査読有り

    Tetsuya Kajita, Takashi Itoh

    Physical Chemistry Chemical Physics 20 (4) 2188-2195 2018年

    出版者・発行元:Royal Society of Chemistry

    DOI: 10.1039/c7cp06998g  

    ISSN:1463-9076

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    Energy storage devices using sodium ions have great potential in terms of their low cost, high power, and long life. In particular, there could be a significant cost reduction, because of the abundant resource of sodium. Recently, electro-chemical sodium storage performance has been demonstrated in graphite anodes using ether-based solvents. However, the high power and long life were not compatible in the same ether solution. Here, we demonstrated using mixed ether-based solvents that a long cycle life and high rate capability can coexist in the graphite anodes for sodium-ion batteries. The cycle performance indicated that the discharge capacity retention ratio after 10000 cycles was more than 90% and the capability of 4 A g-1/0.2 A g-1 (40C/2C) was more than 75%. These results could advance the development of sodium storage devices for practical use.

  15. A dual-functional organic p–n bilayer catalyst comprising a perylene derivative and cobalt phthalocyanine working under illumination and in the dark 査読有り

    Toshiyuki Abe, Masato Okumura, Yuko Kikuchi, Takashi Itoh, Keiji Nagai

    Journal of Materials Chemistry A 5 (16) 7445-7450 2017年4月

    出版者・発行元:None

    DOI: 10.1039/c7ta00174f  

    ISSN:2050-7488

    eISSN:2050-7496

  16. Ether-based solvents significantly improved electrochemical performance for Na-ion batteries with amorphous GeOx anodes 査読有り

    Tetsuya Kajita, Takashi Itoh

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (2) 1003-1009 2017年1月

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/c6cp06354c  

    ISSN:1463-9076

    eISSN:1463-9084

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    We have previously synthesized highly amorphous GeOx powder by a soft chemical method and demonstrated its performance in electrochemical Na insertion-extraction reactions. However, electrolyte decomposition caused large irreversible capacity decay in the first charge-discharge, leading to poor cycling ability. Electrolyte decomposition was accelerated by the large volume change of amorphous GeOx during charge-discharge. Herein, we report the use of ether-based solvents in Na-ion batteries with amorphous GeOx anodes. XPS measurements were used to evaluate the surface state of the electrode after cycling. The surface layer of the electrolyte decomposition products was thin and mainly composed of Na alkoxide. Thus, the electrochemical performance of this system was greatly improved owing to the significant suppression of electrolyte decomposition. Consequently, electrolytes using ether-based solvents are strong candidates for practical use in Na-ion batteries.

  17. Effect of Vanillin to Prevent the Dendrite Growth of Zn in Zinc-Based Secondary Batteries 査読有り

    Mukkannan Azhagurajan, Akiyoshi Nakata, Hajime Arai, Zempachi Ogumi, Tetsuya Kajita, Takashi Itoh, Kingo Itaya

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 164 (12) A2407-A2417 2017年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/2.0221712jes  

    ISSN:0013-4651

    eISSN:1945-7111

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    Although considerable research efforts have been taken to minimize the dendrite growth of zinc in zinc-based secondary batteries, still dendrite growth is a severe issue, which needs further research in this field. In this paper, we have investigated that vanillin as an additive material either eliminates, or assist to minimize the formation of dendrite growth during the deposition of Zn. More than 300 cycles of charge-discharge curves are tested and even at relatively large current densities, dendrite-free zinc surfaces are observed with small amount of vanillin (0.5-5 mM). On the other hand, dendrite growth was observed in the vanillin-free solution. In order to observe the dynamic zinc deposition process on ultra-flat Au(111), we have used an advanced optical microscopy with differential interference microscopy which allowed us to follow the time dependent processes of deposition and dissolution of Zn at high speed accusation times (4 similar to 10 frames/sec even in large area of 100 x 100 mu m). We also found that the formation of "black" films depends on the applied electrode potentials. It is anticipated that such insoluble films might be a key factor for the formation and growth of zinc dendrites in rechargeable zinc batteries. (C) 2017 The Electrochemical Society. All rights reserved.

  18. Ultra-High-Resolution Differential Interference Microscopy of Ag Deposition on an Ultraflat Au(111) 査読有り

    M. Azhagurajan, T. Itoh, K. Itaya

    JOURNAL OF PHYSICAL CHEMISTRY C 120 (29) 16221-16227 2016年7月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/acs.jpcc.6b01668  

    ISSN:1932-7447

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    The electrodeposition of silver on an atomically ultraflat surface of Au(111) was investigated using laser confocal microscopy combined with the differential interference contrast microscopy (LCM-DIM) in the sulfuric acid medium with silver sulfate as an electrolyte solution. For the first time, we have observed the underpotential deposition processes of silver atoms on the large Au(111) surface area in atomic height resolution of as-deposited Ag layers using LCM-DIM. In underpotential deposition (UPD) regions, small islands of Ag atoms with monatomic step heights are formed on the Au(111) terraces at the initial stage, followed by the increase in domain size of islands, and then finally a complete monolayer was formed on the Au(111) surface. Before initiating the bulk deposition of Ag, our LCM-DIM gave direct evidence for the formation of the third monolayer of Ag at the foot of the potential of the bulk deposition. addition to UPD, the bulk deposition of Ag was also investigated which demonstrated that the very flat Ag surface appeared on the Au(111) surface. Finally, it has been demonstrated that the LCM-DIM was an ideal tool to capture images of the fast dynamic Ag electrodeposition processes on the Au(111) surface with the fastest acquisition times of 2-10 frames per second.

  19. In Situ Electrochemical Raman Spectroscopy of Air-Oxidized Semiconducting Single-Walled Carbon Nanotube Bundles in Aqueous Sulfuric Acid Solution 査読有り

    Shin-ichi Ogino, Takashi Itoh, Daiki Mabuchi, Koji Yokoyama, Kenichi Motomiya, Kazuyuki Tohji, Yoshinori Sato

    JOURNAL OF PHYSICAL CHEMISTRY C 120 (13) 7133-7143 2016年4月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/acs.jpcc.5b12057  

    ISSN:1932-7447

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    In this study, we oxidized approximately 90% semiconducting, highly crystalline single-walled carbon nanotube (hc-SWCNT) bundles in the atmosphere at 450 degrees C for 30 min to obtain SWCNTs modified with oxygen-containing functional groups and investigated not only the influence of air oxidation on the electrochemical doping of the air-oxidized SWCNT (AO-SWCNT) bundles in aqueous sulfuric acid solution using in situ Raman spectroscopy, but also the relationship between the in situ electrochemical Raman data and the properties of electric double-layered supercapacitors (EDLSCs). By oxidizing the hc-SWCNTs in air, AO-SWCNTs with a small diameter distribution could be prepared. When a negative charge was applied to the AO-SWCNTs used as a working electrode in a three-electrode electrochemical cell for in situ Raman spectroscopy, a large downshift of the G(+) line of the AO-SWCNTs was observed compared to that before air oxidation. On increasing the ratio of small-diameter nanotubes/total nanotubes, the Raman data obtained in situ revealed that the effect of the weakening of the C-C bond was stronger than that of the renormalization of the phonon energy. In contrast, in the case of applying a positive charge to the AO-SWCNTs, the magnitude of the upshift of the G(+) line for the AO-SWCNTs was slightly larger than that for the hc-SWCNTs. The influent electric charges per unit mass and the specific capacitances of the AO-SWCNT electrodes for the maximum magnitude of the shift of the G(+) line (10.7 cm(-1)) were 60.1 C/g and 50.1 F/g, respectively, which are larger than those of hc-SWCNT electrodes. In situ Raman spectroscopy is a useful method to simultaneously assess the increase or decrease in the diameter distribution of small nanotubes and the specific capacitances of electric double-layered supercapacitors of chemically functionalized SWCNTs by the magnitude of the shift of the G(+) line compared to unfunctionalized SWCNTs.

  20. Electrochemical sodium storage in amorphous GeOx powder 査読有り

    Tetsuya Kajita, Takashi Itoh

    ELECTROCHIMICA ACTA 195 192-198 2016年3月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.electacta.2016.02.117  

    ISSN:0013-4686

    eISSN:1873-3859

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    The amorphous GeOx (x < 1) was synthesized and investigated its suitability as a Na-ion battery anode. GeOx was synthesized by oxidizing Zintl-phase NaGe with isopropyl alcohol at room temperature. The amorphous GeOx showed good electrochemical Na storage as an anode for Na-ion batteries, with first reversible capacity of 342 mAh g (1), high power of 237 mAh g (1) (6 A g (1)), and cycle performance, retaining a capacity of 216 mAh g (1) after 40 cycles. (C) 2016 Elsevier Ltd. All rights reserved.

  21. In Situ Visualization of Lithium Ion Intercalation into MoS2 Single Crystals using Differential Optical Microscopy with Atomic Layer Resolution 査読有り

    Mukkannan Azhagurajan, Tetsuya Kajita, Takashi Itoh, Youn-Geun Kim, Kingo Itaya

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 (10) 3355-3361 2016年3月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/jacs.5b11849  

    ISSN:0002-7863

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    Atomic-level visualization of the intercalation of layered materials, such as metal chalcogenides, is of paramount importance in the development of high-performance batteries. In situ images of the dynamic intercalation of Li ions into MoS2 single-crystal electrodes were acquired for the first time, under potential control, with the use of a technique combining laser confocal microscopy with differential interference microscopy. Intercalation proceeded via a distinct phase separation of lithiated and delithiated regions. The process started at the atomic steps of the first layer beneath the selvedge and progressed in a layer-by-layer fashion. The intercalated regions consisted of Li-ion channels into which the newly inserted Li ions were pushed atom-by-atom. Interlayer diffusion of Li ions was not observed. Deintercalation was also clearly imaged and was found to transpire in a layer-by-layer mode. The intercalation and deintercalation processes were chemically reversible and can be repeated many times within a few atomic layers. Extensive intercalation of Li ions disrupted the atomically flat surface of MoS2 because of the formation of small lithiated domains that peeled off from the surface of the crystal. The current potential curves of the intercalation and deintercalation processes were independent of the scan rate, thereby suggesting that the rate-determining step was not governed by Butler-Volmer kinetics.

  22. Energy storage in batteries and fuel cells 査読有り

    Tetsuya Kajita, Takashi Itoh

    Lecture Notes in Energy 32 105-122 2016年2月1日

    出版者・発行元:Springer Verlag

    DOI: 10.1007/978-3-319-25400-5_7  

    ISSN:2195-1292 2195-1284

    eISSN:2195-1292

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    Batteries and fuel cells (FCs) are the two major types of solar energy storage devices currently in use. Secondary batteries reversibly convert stored chemical energy (e.g., from solar power devices) into electrical energy. FCs generally convert chemical energy from fuel into electricity via chemical reactions with oxygen. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and methanol are sometimes used. FCs are distinct from batteries in that the former require a constant source of fuel and oxygen (e.g., through solar electrolysis of water) to sustain their chemical reactions, and can continuously produce electricity for as long as these inputs are supplied. A system consisting of stored hydrogen in a cylinder tank and an FC system functions as a battery. In this chapter, we discuss batteries and FCs for use with solar power devices, in terms of current practice and future perspectives.

  23. Electrochemical Performance of Amorphous GeOx Powder Synthesized by Oxidation of NaGe Serving as an Anode for Lithium Ion Batteries 査読有り

    Tetsuya Kajita, Takashi Itoh

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 163 (3) A552-A556 2016年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/2.0931603jes  

    ISSN:0013-4651

    eISSN:1945-7111

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    A highly amorphous GeOx powder has been synthesized by a soft chemical method. The method involves sodium germanium NaGe of Zintl phase was simply oxidized by isopropyl alcohol at room temperature and placed into distilled water. Amorphous GeOx powder serving as an anode for a Li-ion battery exhibited a high reversible capacity of 1268 mAh g(-1), high rate ability of 1035 mAh g(-1) (current rate of 6A g(-1)) and good cycle performance of 930 mAh g(-1) after 30 cycles. Thereby, our amorphous GeOx is to be potential anode material for Li-ion batteries. (C) The Author(s) 2016 Published by ECS. All rights reserved.

  24. 電気化学界面におけるその場ラマン分光解析 招待有り 査読有り

    伊藤 隆

    応用物理 85 (9) 754-760 2016年

    出版者・発行元:応用物理学会

    ISSN:0369-8009

  25. Electrochemical performance of highly amorphous GeOx powders synthesized in different alcohols for use in Na- and Li-ion batteries 査読有り

    T. Kajita, T. Itoh

    RSC ADVANCES 6 (104) 102109-102115 2016年

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/c6ra20794d  

    ISSN:2046-2069

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    We synthesized highly amorphous GeOx powders by a solution synthesis method, in which NaGe was oxidized by alcohol and placed in distilled water. Further, we investigated the effect of the alcohol used during the solution synthesis method on the electrochemical Na- and Li-ion insertion/extraction performances of the powder sample. We compared the oxidation process as performed using various alcohols. The amorphous GeOx powder sample synthesized by oxidation in 2-propanol (secondary alcohol) exhibited good electrochemical performance with respect to Na- and Li-ion insertion/extraction, while the amorphous GeOx powders synthesized using methanol, ethanol, and 1-propanol (primary alcohol) showed poor performances. These powders consisted of large particles, which was the reason for their poor electrochemical performance. In particular, their cycling performance in a Na-ion cell was significantly lowered by the large particle size. Hence, during the solution synthesis process, the use of a secondary alcohol is the key to synthesizing highly amorphous GeOx powders with small particle sizes. Finally, electrolyte decomposition was also found to be one of the main causes for the deterioration of the cycling performance in a Na-ion cell, because the change in the volume of the GeOx particles during charging/discharging was smaller in the Na-ion cell than in a Li-ion cell.

  26. Electrochemical Na-intercalation-induced high-temperature superconductivity in FeSe 査読有り

    Tetsuya Kajita, Takayuki Kawamata, Takashi Noji, Takehiro Hatakeda, Masatsune Kato, Yoji Koike, Takashi Itoh

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 519 104-107 2015年12月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physc.2015.09.005  

    ISSN:0921-4534

    eISSN:1873-2143

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    Iron-chalcogenide-based superconductors have attracted much attention due to theft relatively high superconducting transition temperatures (T-c) and their simple layered crystal structures. We have performed electrochemical co-intercalation of Na and propylene carbonate (PC) into FeSe, and successfully synthesized a new superconductor, Na-x(PC)(y)Fe2Se2, with T-c = 43 K. The type and amount of intercalated metal, and the electrolyte used in the intercalation affected the superconductivity. Our electrochemical intercalation method should be a useful tool for discovering new superconductors by controlling the intercalation conditions. (C) 2015 Elsevier B.V. All rights reserved.

  27. Green synthesis and formation mechanism of nanostructured Bi2Te3 using ascorbic acid in aqueous solution 査読有り

    Shun Yokoyama, Keita Sato, Makoto Muramatsu, Takehiro Yamasuge, Takashi Itoh, Kenichi Motomiya, Hideyuki Takahashi, Kazuyuki Tohji

    ADVANCED POWDER TECHNOLOGY 26 (3) 789-796 2015年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apt.2015.02.002  

    ISSN:0921-8831

    eISSN:1568-5527

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    Nanostructured Bi2Te3 can be synthesized in 100% yield by a chemical reduction method in aqueous TeO32 solution using mild and safe ascorbic acid as reducing agent instead of toxic reducing agent commonly employed. Additionally, ascorbic acid works not only as reducing agent but also as capping agent which has an excellent oxidation resistance. In general, ascorbic acid cannot directly reduce TeO32 to metal Te due to the lower reduction potential of TeO32. Electrochemical analysis and ESI-TOFMS study showed that TeO32 changes to metal Te via easily reducible Te species with ascorbic acid [TeO2(C6H6O6)](2), and subsequently metal Te triggers the reduction of Bi species, resulting in the Bi2Te3 nanoparticles. This finding creates a path of green synthesis method for nanostructured metal tellurides which have various applications. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan. All rights reserved.

  28. Preparation and characterization of ultraflat Pt facets by atom-height-resolved differential optical microscopy 査読有り

    M. Azhagurajan, R. Wen, Y. G. Kim, T. Itoh, K. Sashikata, K. Itaya

    SURFACE SCIENCE 631 57-62 2015年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.susc.2014.07.031  

    ISSN:0039-6028

    eISSN:1879-2758

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    We recently demonstrated that improvements to our technique, laser confocal microscopy with differential interference microscopy (LCM-DIM), has rendered it fully capable of resolving monatomic steps with heights of ca. 0.25 nm on Au(111) and Pd(111) surfaces, even as low as 0.14 nm on Si(100), in aqueous solution. In this paper, we describe in detail a method to prepare and characterize, via atomic-layer-resolved LCM-DIM, ultraflat Pt(111) and Pt(100) facets over a wide surface area. The preparation of ultraflat surfaces is important in the characterization at the atomic scale of electrochemical processes under reaction conditions. To showcase the elegance of LCM-DIM, the anodic dissolution of Pt in aqueous HCl is briefly recounted. (C) 2014 Elsevier B.V. All rights reserved.

  29. Structural and Electrochemical Characterization of Ethylenediaminated Single-Walled Carbon Nanotubes Prepared from Fluorinated SWCNTs 査読有り

    Kohei Bushimata, Shin-ichi Ogino, Kazutaka Hirano, Tatsuhiro Yabune, Kenta Sato, Takashi Itoh, Kenichi Motomiya, Koji Yokoyama, Daiki Mabuchi, Hikaru Nishizaka, Go Yamamoto, Toshiyuki Hashida, Kazuyuki Tohji, Yoshinori Sato

    JOURNAL OF PHYSICAL CHEMISTRY C 118 (27) 14948-14956 2014年7月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/jp503124n  

    ISSN:1932-7447

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    We prepared ethylenediaminated single-walled carbon nanotubes (SWCNTs) from fluorinated SWCNTs by substituting fluorine groups with ethylenediamine groups. The ethylenediaminated SWCNTs were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman scattering spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area measurement by nitrogen adsorption, contact angle measurement, zeta potential analysis, and thermogravimetry. In addition, the properties of 30 wt % sulfuric acid aqueous electrolyte-based electric double-layer supercapacitors (EDLSCs) with free-standing ethylenediaminated SWCNT electrodes were investigated. The degree of ethylenediamine functionalization was 0.603 mmol/g and 1.46 mu mol/m(2), and the specific surface area was similar to 413.3 m(2)/g. From HRTEM observation, isolated nanotubes disentangled from the bundled SWCNTs were present in many observed areas, and the structures retained a nanotube skeleton. The properties of the EDLSCs with the ethylenediaminated SWCNT electrodes included an average specific capacitance of 94 F/g at a low scan rate of 10 mV/s and an energy density of 2.6 Wh/kg at a power density of 0.24 kW/kg. The EDLSCs exhibited an average specific capacitance of 67 F/g at a high scan rate of 1000 mV/s and an energy density of 1.3 Wh/kg at a power density of 24 kW/kg, values that were superior to those of carboxylated SWCNT electrodes.

  30. Synthesis of metallic Cu nanoparticles by controlling Cu complexes in aqueous solution 査読有り

    Shun Yokoyama, Hideyuki Takahashi, Takashi Itoh, Kenichi Motomiya, Kazuyuki Tohji

    ADVANCED POWDER TECHNOLOGY 25 (3) 999-1006 2014年5月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apt.2014.01.024  

    ISSN:0921-8831

    eISSN:1568-5527

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    We report an easy synthesis method of copper nanoparticles (NPs) through controlling Cu complexes by using citric acid in an aqueous solution under atmospheric condition at room temperature. By controlling the Cu complexes based on the calculation of pH dependent metal complex concentrations in the aqueous solution and analyzing the redox potential of Cu complexes electrochemically, the relationships between Cu complexes formed at each pH and the size of Cu NPs were elucidated. Although the Cu-citric acid complexes were expected to be the same in the pH range from 11 to 13, linear sweep voltammogram results strongly indicate that Cu-citric acid complexes at pH 13 are quite different from those at pH 11 and 12. ESI-TOFMS results represent that hydroxide ions bond to the Cu citrate acid complex at pH 13 and consequently (Cu2+)(C6H4O74-)(OH-)(2) is formed. The Cu complex at pH 13 is easily reduced to Cu NPs compared with Cu-citric acid complex formed at pH 11 and 12. As a result, the size of Cu NPs at pH 13 is smaller than that of Cu NPs at pH 11 and 12. In summary, the control of metal complex is found to be crucial for synthesis of Cu NPs in the aqueous solution. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

  31. In Situ Surface-enhanced Raman Analysis of Water Libration on Silver Electrode in Various Alkali Hydroxide Aqueous Solutions 査読有り

    Takashi Itoh, Tetsuya Kajita, Toshiteru Maeda, Atsuo Kasuya

    ELECTROCHEMISTRY 82 (5) 396-400 2014年5月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    DOI: 10.5796/electrochemistry.82.396  

    ISSN:1344-3542

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    Water libration on a silver electrode in various alkali hydroxides (MOH, M = Li, Na, K or Cs) aqueous solutions was examined through simultaneous experiments using surface-enhanced Raman scattering (SERS) and electrochemical analysis. This technique, referred to as SERS spectroelectrochemistry, reveals the Raman spectral band between 200 and 750 cm(-1), assignable to water libration on the electrode surface, through electrode potential scanning. The Raman intensity in this spectral band changes with the electrode potential. The variation in Raman intensity of water libration observed when scanning the electrode potential is discussed in terms of water molecules at the electrode interface in various alkali hydroxide aqueous solutions. (c) The Electrochemical Society of Japan, All rights reserved.

  32. Synthesis of CaMn<inf>2</inf>O<inf>4</inf>-related electrocatalyst for Oxygen evolution electrode of watersplitting

    Yuya Taki, Zhenquan Tan, Satoshi Ohara, Takashi Itoh, Yoshiaki Nakano, Katsushi Fujii, Masakazu Sugiyama

    Materials Research Society Symposium Proceedings 1640 (January) 12-17 2014年

    DOI: 10.1557/opl.2014.406  

    ISSN:0272-9172

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    © 2014 Materials Research Society. Water-splitting by using electric power produced by solar cells is promising system to produce hydrogen without fossil fuels. Oxygen evolving catalyst is, however, major problem to prevent using this system widely because precious materials are used in the catalyst. Considering from the photosynthesis II of plants, the compound of Ca-Mn-0 is one of the candidates for the oxygen evolving catalyst. In this study, the synthesis condition and the oxygen evolving electrocatalytic activity of CaMn2O4•xH2O are investigated. The overpotential at 0.1 mA/cm2 was 0.28 V when using the electrode of carbon paste and CaMn2O4•H2O with the weight ratio of 3:1.

  33. Surface modification of Cu metal particles by the chemical reaction between the surface oxide layer and a halogen surfactant 査読有り

    Shun Yokoyama, Hideyuki Takahashi, Takashi Itoh, Kenichi Motomiya, Kazuyuki Tohji

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 75 (1) 68-73 2014年1月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jpcs.2013.08.010  

    ISSN:0022-3697

    eISSN:1879-2553

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    Surface oxides on small (2-5 mu m) copper metal particles can be removed by chemical reaction with tris (2,3-dibromopropyl) isocyanurate (TIC) in diethylene glycol mono-n-hexyl ether (DGHE) solution under mild conditions where metal particles are not damaged. Surface oxides convert to copper bromide species and subsequently dissolve into the solvent. It was found that resultant surface species are resistant to re-oxidation due to remaining surface bromides. This finding opens up a possibility to create microclines based on cheap copper nanoparticles. (C) 2013 Elsevier Ltd. All rights reserved.

  34. Orbital-specific Tunability of Many-Body Effects in Bilayer Graphene by Gate Bias and Metal Contact 査読有り

    Hirokazu Fukidome, Masato Kotsugi, Kosuke Nagashio, Ryo Sato, Takuo Ohkochi, Takashi Itoh, Akira Toriumi, Maki Suemitsu, Toyohiko Kinoshita

    SCIENTIFIC REPORTS 4 3713-1-3713-5 2014年1月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/srep03713  

    ISSN:2045-2322

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    Graphene, a 2D crystal bonded by p and sigma orbitals, possesses excellent electronic properties that are promising for next-generation optoelectronic device applications. For these a precise understanding of quasiparticle behaviour near the Dirac point (DP) is indispensable because the vanishing density of states (DOS) near the DP enhances many-body effects, such as excitonic effects and the Anderson orthogonality catastrophe (AOC) which occur through the interactions of many conduction electrons with holes. These effects renormalize band dispersion and DOS, and therefore affect device performance. For this reason, we have studied the impact of the excitonic effects and the AOC on graphene device performance by using X-ray absorption spectromicroscopy on an actual graphene transistor in operation. Our work shows that the excitonic effect and the AOC are tunable by gate bias or metal contacts, both of which alter the Fermi energy, and are orbital-specific.

  35. Novel nickel-palladium catalysts encased in a platinum nanocage 査読有り

    Balachandran Jeyadevan, Jhon L. Cuya, Yoshinori Inoue, Kozo Shinoda, Takashi Ito, Derrick Mott, Koichi Higashimine, Shinya Maenosono, Takatoshi Matsumotob, Hiroshi Miyamuraa

    RSC ADVANCES 4 (51) 26667-26672 2014年

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/c4ra03091e  

    ISSN:2046-2069

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    Novel Ni-Pd nanocubes of a few tens of nm in size encased in a Pt cage have for the first time been synthesized using a long-chain alcohol reduction process. The unique distribution of Pt atoms in these particles holds the key for the design of high turnover catalysts for the future.

  36. Elucidation of the reaction mechanism during the removal of copper oxide by halogen surfactant at the surface of copper plate 査読有り

    Shun Yokoyama, Hideyuki Takahashi, Takashi Itoh, Kenichi Motomiya, Kazuyuki Tohji

    Applied Surface Science 264 664-669 2013年1月1日

    DOI: 10.1016/j.apsusc.2012.10.088  

    ISSN:0169-4332

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    Although copper nanoparticles have various attractive properties, electrical applications of these was not achieved because of its surface oxide layer which prohibited electrical conduction. Thus, it can be considered that a new elimination method of the oxide on Cu surface, which simultaneously provide the resistance to re-oxidized, should be developed. In this study, the reaction between the metal oxide on Cu plate surface and halogen surfactant was introduced into development as a new elimination method of surface oxide layer. Since electrochemical and surface analysis are effective for analyzing the reaction mechanism which expected to be the reduction reaction of the oxide on metal surface, Cu electrode, which represented material of Cu nanoparticles surface, was used for the reaction mechanism analysis. The oxide is removed by controlling the temperature and selecting the optimal combination of solvents and the halogen surfactant (TIC). Results of electrochemical measurements strongly suggest that the chemical reaction between the oxides on the surface with the halogen surfactant is a substitution reaction which converts Cu oxide to Cu bromide, and continuously formed Cu bromide was dissolved into solvent. Totally, the oxide on the Cu surface was successfully eliminated. © 2012 Elsevier B.V. All rights reserved.

  37. Direct Evidence of Homoepitaxial Growth in the Electrodeposition of Au Observed by Ultra-High Resolution Differential Optical Microscopy 査読有り

    M. Azhagurajan, R. Wen, A. Lahiri, Y. G. Kim, T. Itoh, K. Itaya

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 160 (9) D361-D365 2013年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/2.057309jes  

    ISSN:0013-4651

    eISSN:1945-7111

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    The combination of our improved laser confocal microscopy with the differential interference microscopy technique (LCM-DIM) is capable of resolving the monatomic steps with heights of ca. 0.25 nm on Au(111) and Pd(111) surfaces and even 0.14 nm on Si(100) in aqueous solutions. LCM-DIM can also follow dynamic movement of monatomic steps in a large area with short acquisition times,(2-10 frames/s), indicating that the LCM-DIM is a powerful in-situ method for evaluating various reactions at solid/liquid interfaces with atomic layer resolution. In this paper, we demonstrate the capability of LCM-DIM for the evaluation of the electrodeposition of Au on an Au(111) surface. It is shown that the Au deposition occurs mainly at atomic steps resulting the layer-by-layer growth at potentials near the onset of cathodic currents over the entire area (ca. 100 x 100 mu m square). New small islands with a monatomic height were also observed on atomically flat terraces during the deposition. These islands expanded in the lateral direction, resulting the formation of new layers. LCM-DIM provides direct images of dyammic growth modes in the electrochemical deposition of Au with an atomic layer resolution. (C) 2013 The Electrochemical Society. All rights reserved.

  38. Spectroscopic characterization of dragonfly wings common in Japan 査読有り

    Akira Yoshihara, Atsushi Miyazaki, Toshiteru Maeda, Yoshika Imai, Takashi Itoh

    VIBRATIONAL SPECTROSCOPY 61 85-93 2012年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.vibspec.2012.03.010  

    ISSN:0924-2031

    eISSN:1873-3697

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    A series of Fourier Transform infrared (FT-IR) absorption, X-ray diffraction (XRD), and Brillouin light scattering (BLS) studies on the wings of six species of dragonfly common in Japan, including the largest Anotogaster sieboldii and much smaller Lestes tempo rails, was performed at room temperature. XRD and FT-IR results indicate that dragonfly wing is comprised of a randomly oriented microcrystalline or an amorphous-like a-chitin. We observed a pair of longitudinal acoustic (LA) phonon peaks and a broad quasi-elastic scattering peak in backscattering BLS spectra. LA phonon frequencies and full widths at half maximum were found to be 19.5 +/- 0.4 GHz and 1.0 +/- 0.2 GHz for the 488 nm excitation and independent of their sizes and species. (C) 2012 Elsevier B.V. All rights reserved.

  39. Photoluminescence changes in n-type GaN samples after photoelectrochemical treatment 査読有り

    Katsushi Fujii, Kayo Koike, Mika Atsumi, Takenari Goto, Takashi Itoh, Takafumi Yao

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4 9 (3-4) 715-718 2012年

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/pssc.201100310  

    ISSN:1862-6351

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    Photoelectrochemical water splitting using semiconductors to produce hydrogen is a promising technique for converting sunlight to chemical energy. However, anodic photocorrosion occurs during the reaction even when n-type GaN, a chemically stable material, is used for the photo-illuminated working electrode. We previously demonstrated that the stability is related to the amount of Si doping used to make the GaN to be n-type. This means that, the surface damage after photoelectrochemical reaction depends on the amount of Si. We have now investigated the relationship between this surface change and the optical properties especially for the near band edge peaks. With the peak shift by the strain relaxation due to the surface change from smooth to rough, new peaks around 3.4 eV were observed after photoelectrochemical treatment. These new peaks are defect-related emission, which has been reported as Y-i lines. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  40. In Situ 測定,ラマン分光法-リチウムイオン電池- 招待有り 査読有り

    伊藤隆

    Electrochemistry 79 (11) 907-910 2011年11月1日

    出版者・発行元:The Electrochemical Society of Japan

    DOI: 10.5796/electrochemistry.79.907  

    ISSN:1344-3542

  41. Molecular Hydrogen Evolution by Organic p/n Bilayer Film of Phthalocyanine/Fullerene in the Entire Visible-Light Energy Region 査読有り

    Toshiyuki Abe, Shunsuke Tobinai, Naohiro Taira, Junpei Chiba, Takashi Itoh, Keiji Nagai

    JOURNAL OF PHYSICAL CHEMISTRY C 115 (15) 7701-7705 2011年4月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/jp1094992  

    ISSN:1932-7447

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    This article presents a novel approach to photo-chemical energy conversion by employing organic compounds. We demonstrated that water can be photoelectrochemically split into H-2 and O-2 using an organic photodevice responsive to the entire visible-light energy range of &lt; 750 nm. When an organic p/n bilayer of metal-free phthalocyanine (H2Pc, a p-type semiconductor) and fullerene (C-60,C- an n-type semiconductor) was applied to a photocathode in the water phase, H-2 was evolved at Pt-coated C-60 along with the conductin of the electron carriers photogenerated at the p/n interface, concurrently yielding O-2 at the counter electrode. This is the first example of C-60 participation in H-2 evolution: a mechanism was proposed, involving the formation of an active species (i.e., C-60(2-)) on the basis of the results of in situ spectroelectrochemical measurements.

  42. Effects of GaN thin layer on InGaN at electrolyte-semiconductor interface for the application of photoelectrochemical water splitting 査読有り

    Katsushi Fujii, Kayo Koike, Mika Atsumi, Takashi Itoh, Takenari Goto, Takafumi Yao, Masakazu Sugiyama, Yoshiaki Nakano

    Materials Research Society Symposium Proceedings 1387 16-21 2011年

    DOI: 10.1557/opl.2012.769  

    ISSN:0272-9172

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    Photoelectrochemical properties of nitride semiconductors are paid attention due to their possibilities of water splitting by visible light absorption. However, the photocurrent density of InxGa 1-xN, which absorbs visible light, is usually lower than that of GaN, which has larger band-gap and absorbing only UV light. The reasons of this are thought to be the band-edge position at the semiconductor-electrolyte interface and the crystal quality. The conduction band-edge decreases with increasing of indium composition and across the hydrogen generation energy at around the indium composition of 0.2. This means that the hydrogen generation ability decreases with increasing of indium composition. Low crystal quality is obtained because the lower growth temperature of InxGa1-xN than that of GaN to achieve the indium incorporation. In order to improve the photocurrent density, band-edge energy control and quantum tunneling effect are tried using the structure of thin GaN layer on InxGa1-xN here. The effect for the photocurrent densities is also discussed. © 2012 Materials Research Society.

  43. Time dependence of water-reducing photocurrent with change of the characteristics of n-type GaN photo-illuminated working electrodes 査読有り

    Katsushi Fujii, Kayo Koike, Mika Atsumi, Takenari Goto, Takashi Itoh, Takafumi Yao

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 7-8 8 (7-8) 2457-2459 2011年

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/pssc.201000937  

    ISSN:1862-6351

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    Nitride semiconductors are expected for the working electrodes of photoelectrochemical water splitting due to the chemical stability and band-gap configuration. The p-type nitrides are stable under photoelectrochemical conditions but the efficiency of light to hydrogen energy is low. The n-type nitrides have relatively high energy-conversion especially for the quantum efficiency, but the photoelectrochemical reaction is not stable because of the anodic photocorrosion. In this article, the relationships between the characteristics of n-type GaN and the photocurrent stability are discussed. The amount of Si doping was clarified to relate to the stability. The suitable properties for stable photocurrent were different from those for high energy-conversion efficiency at initial stage. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  44. Mechanical and tribological properties of boron, nitrogen-coincorporated diamond-like carbon films prepared by reactive radio-frequency magnetron sputtering 査読有り

    H. Nakazawa, A. Sudoh, M. Suemitsu, K. Yasui, T. Itoh, T. Endoh, Y. Narita, M. Mashita

    DIAMOND AND RELATED MATERIALS 19 (5-6) 503-506 2010年5月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.diamond.2010.01.026  

    ISSN:0925-9635

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    We have deposited boron- and/or nitrogen-incorporated DLC films by radio-frequency magnetron sputtering, and systematically investigated the structure and the mechanical and tribological properties. The N content in DLC films increased with increasing N(2) flow ratio [N(2)/(Ar + N(2))], and it tended to be saturated at higher N(2) flow ratios. The N content further increased with an increase in the B content of the targets. The B/C ratios of the films were almost the same as those of the B-containing targets regardless of the N content. Scratch tests revealed that the adhesion strength of N-incorporated DLC films decreased with increasing N(2) flow ratio and the critical loads of B-incorporated films were lower than that of an unincorporated film. It was found that for B. N-coincorporated films there was an optimum N(2) flow ratio at which the critical load became a maximum value, which was higher than that of the unincorporated film. The optimum N(2) flow ratio increased with an increase in the B composition of the targets. The N-incorporated films peeled off during ball-on-plate friction tests. On the other hand, the B, N-coincorporated films showed good wear-resistant properties that the specific wear rates were lower than those of the unincorporated and B-incorporated films. (C) 2010 Elsevier B.V. All rights reserved.

  45. Inhibition of the Dissolution of Fe from Fe-Pt Nano Particles by a Structural Phase Transitions 査読有り

    Takashi Itoh, Masaki Uebayashi, Kazuyuki Tohji, Balachandran Jeyadevan

    ELECTROCHEMISTRY 78 (2) 157-160 2010年2月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    DOI: 10.5796/electrochemistry.78.157  

    ISSN:1344-3542

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    Fe-Pt nanoparticles fabricated by the polyol process have been reported as a possible alternative material for use in catalytic electrodes for polymer electrolyte fuel cells (PEFCs). Catalytic Fe-Pt alloys suffer from a problem where Fe dissolves from the alloy. Here, we examined the dissolution of Fe into the electrolyte for various composition ratios of Fe to Pt. We have also described the characteristics of Fe-Pt nanoparticles oil the basis of XRD, XRF, TEM-EDX and electrochemical measurements and have discussed the rinse effect of Fe-Pt nanoparticles in acid solutions and the annealing effect of Fe-Pt caused by structural phase transitions from disordered fcc to ordered fct phase structures.

  46. 再生可能サイクルへ向けた環境電気化学エネルギー変換デバイス 査読有り

    伊藤隆

    Electrochemistry 78 (1) 50-75 2010年

    出版者・発行元:電気化学会

    ISSN:1344-3542

  47. 電極材料の過剰な負荷条件下におけるその場ラマン分光解析 招待有り 査読有り

    伊藤隆

    FC Reports 28 (2) 44-48 2010年

    出版者・発行元:日本ファインセラミックス協会

    ISSN:0911-5269

  48. Effects of Silicon Source Gas and Substrate Bias on the Film Properties of Si-Incorporated Diamond-Like Carbon by Radio-Frequency Plasma-Enhanced Chemical Vapor Deposition 招待有り 査読有り

    Hideki Nakazawa, Takeshi Kinoshita, Yuhta Kaimori, Yuhki Asai, Maki Suemitsu, Toshimi Abe, Kanji Yasui, Tetsuo Endoh, Takashi Itoh, Yuzuru Narita, Yoshiharu Enta, Masao Mashita

    JAPANESE JOURNAL OF APPLIED PHYSICS 48 (11) 116002-1-116002-8 2009年11月

    出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS

    DOI: 10.1143/JJAP.48.116002  

    ISSN:0021-4922

    eISSN:1347-4065

    詳細を見る 詳細を閉じる

    We have deposited Si-incorporated diamond-like carbon (DLC) films by radio-frequency plasma-enhanced chemical vapor deposition using methane, argon, and organosilanes, and investigated the effects of Si source gas (monomethylsilane, dimethylsilane) and substrate bias (negative do bias, negative pulse bias) on the structure and the mechanical and tribological properties of the films. The Si-DLC films deposited using monomethylsilane as a Si source gas tended to have a higher Si atomic fraction ratio [Si/(Si + C)] than the films deposited using dimethylsilane. Friction coefficient and internal stress decreased by the incorporation of Si into the films. However, many particles composed mainly of Si were observed on the film surfaces when deposition using a do bias was carried out at higher monomethylsilane or dimethylsilane flow ratios. It was found that for both the Si source gases, the use of a pulse bias was effective in suppressing the formation of particles and further decreasing friction coefficient and internal stress Additionally, the pulse-biased Si-DLC films were found to have a higher wear resistance than the dc-biased Si-DLC films. (C) 2009 The Japan Society of Applied Physics

  49. 間欠ガス供給を用いたホットメッシュCVD法によるSi上GaNエピタキシャル成長 査読有り

    齋藤健, 永田一樹, 西山洋, 末光眞希, 伊藤隆, 遠藤哲郎, 中澤日出樹, 成田克, 高田雅介, 赤羽正志, 安井寛治

    電子情報通信学会 電子部品・材料研究会 109 (171) 61-66 2009年8月11日

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    GaNの省資源成長法として期待されるホットメッシュCVD法において、原料ガスの間欠供給がGaN結晶膜の特性にどのような効果をもたらすか調べた。これまでAlNバッファー層成長過程においていくつかの間欠ガス供給パターンを用いてGaNの成長を行った。このAlNバッファー層形成条件についてはGaN結晶性向上にとって良好な条件を見出せたが、GaN膜の成長過程において最適な間欠ガス供給条件を見出していない。今回、気相反応を抑制することでGaN膜の特性を更に改善出来ないか、アンモニア及びアルキル金属原料ガスを間欠供給させ成長を行った。また、1パルスあたりのTMGの供給量を制御しGaN成長を試みた。その結果、TMGを間欠供給、アンモニアを連続供給させた場合において結晶性、発光特性ともに優れたGaN膜が得られた。また、Ga原料ガス原料供給の周期8秒で最も良い結晶膜が得られた。

  50. 有機シランを用いたプラズマCVD法によるダイヤモンドライクカーボン薄膜の膜特性評価 査読有り

    三浦創史, 中澤日出樹, 西崎圭太, 末光眞希, 安井寛治, 伊藤隆, 遠藤哲郎, 成田克

    電子情報通信学会技術研究報告 vol. 109 (No. 171) 13-18 2009年8月10日

  51. Epitaxial Growth of GaN Films by Pulse-Mode Hot-Mesh Chemical Vapor Deposition 査読有り

    Yasuaki Komae, Kanji Yasui, Maki Suemitsu, Tetsuo Endoh, Takashi Ito, Hideki Nakazawa, Yuzuru Narita, Masasuke Takata, Tadashi Akahane

    JAPANESE JOURNAL OF APPLIED PHYSICS 48 (7) 076509-1-076509-5 2009年7月

    出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS

    DOI: 10.1143/JJAP.48.076509  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    Intermittent gas supplies for hot-mesh chemical vapor deposition (CVD) for the epitaxial growth of gallium nitride (GaN) films were investigated to improve film crystallinity and optical properties. The GaN films were deposited on SiC/Si(111) substrates using an alternating-source gas supply or an intermittent supply of source gases such as ammonia (NH(3)) and trimethylgallium (TMG) in hot-mesh CVD after deposition of an aluminum nitride (AlN) buffer layer. The AlN layer was deposited using NH(3) and trimethylaluminum (TMA) on a SiC layer grown by carbonization of a Si substrate using propane (C(3)H(8)). GaN films were grown on the AlN layer by a reaction between NH(x) radicals generated on a ruthenium (Ru)-coated tungsten (W) mesh and TMG molecules. After testing various gas supply modes, GaN films with good crystallinity and surface morphology were obtained using an intermittent supply of TMG and a continuous supply of NH(3) gas. An optimal interval for the TMG gas supply was also obtained for the apparatus employed. (C) 2009 The Japan Society of Applied Physics

  52. Atomic hydrogen etching of silicon-incorporated diamond-like carbon films prepared by pulsed laser deposition 査読有り

    H. Nakazawa, H. Sugita, Y. Enta, M. Suemitsu, K. Yasui, T. Itoh, T. Endoh, Y. Narita, M. Mashita

    DIAMOND AND RELATED MATERIALS 18 (5-8) 831-834 2009年5月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.diamond.2008.10.043  

    ISSN:0925-9635

    詳細を見る 詳細を閉じる

    We have deposited Si-DLC films by pulsed laser deposition using KrF excimer laser, and have investigated etching of the Si-DLC films by atomic hydrogen. We have examined the structure and chemical bonding of the films by Raman spectroscopy, X-ray photoelectron spectroscopy and photoelectron spectroscopy using synchrotron radiation. Photoelectron spectra of Si 2p with 135 eV photons showed two distinguishing components. The main components were identified with Si-C and silicon oxides. The intensity of the oxide component increased when the detection angle to the surface normal was increased from 0 to 60 degrees, indicating that thin oxide layers were formed at the surface. The oxide component decreased by annealing at a substrate temperature above 850 degrees C in an ultra-high vacuum and it disappeared at 1050 degrees C. We found that the etching rate of the films drastically decreased by the incorporation of Si. It was also found that the etching rate of the Si-DLC films markedly increased after dipping in a HF solution, indicating that the hydrogen etching of the Si-DLC films is suppressed by thin oxide layers formed at the surfaces. When the HF-treated Si-DLC films were annealed at a temperature above 400 degrees C in a high vacuum chamber, the etching rate decreased, suggesting that oxide layers were formed again at the surfaces. (C) 2008 Elsevier B.V. All rights reserved.

  53. The growth of GaN films by alternate source gas supply hot-mesh CVD method 査読有り

    Yasuaki Komae, Takeshi Saitou, Maki Suemitsu, Takashi Ito, Tetsuo Endoh, Hideki Nakazawa, Yuzuru Narita, Masasuke Takata, Tadashi Akahane, Kanji Yasui

    THIN SOLID FILMS 517 (12) 3528-3531 2009年4月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.tsf.2009.01.021  

    ISSN:0040-6090

    詳細を見る 詳細を閉じる

    Gallium nitride (GaN) films and Aluminium nitride (AIN) layers were deposited on SiC/Si (111) substrates by an alternating source gas supply or an intermittent supply of a source gas such as ammonia (NH(3)), trimethylgallium (TMG) or trimethylaluminum (TMA) in a hot-mesh chemical vapor deposition (CVD) apparatus. The AIN layer was deposited as a buffer layer using NH3 and TMA on a SiC layer grown by carbonization on Si substrates using propane (C(3)H(8)). GaN films were grown on an AIN layer by a reaction between NH(x) radicals generated on a ruthenium (Ru) coated tungsten (W)-mesh and TMG molecules. An alternating source gas supply or an intermittent supply of one of the source gases during the film growth are expected to be effective for the suppression of gas phase reactions and for the enhancement of precursor migration on the substrate surface. By the intermittent supply of alkylmetal gas only during the growth of the AIN layer, the defect generation in the GaN films was reduced. GaN film growth by intermittent supply on an AIN buffer layer, however, did not lead to the improvement of the film quality. (C) 2009 Elsevier B.V. All rights reserved.

  54. Si 原料に有機シランを用いたプラズマCVD 法によるSi 添加DLC 膜の膜特性評価 査読有り

    三浦創史, 中澤日出樹, 西崎圭太, 末光眞希, 安井寛治, 伊藤隆, 遠藤哲郎, 成田克

    2009年春季第56回応用物理関係連合講演会 2009年3月31日

  55. ホットメッシュCVD法を用いたGaN成長におけるパルスガス供給の効果 査読有り

    齋藤 健, 小前泰彰, 西山洋, 末光眞希, 伊藤 隆, 遠藤哲郎, 中澤日出樹, 成田 克, 高田雅介, 赤羽正志, 安井寛治

    日本物理学会春季大会 2009年3月30日

  56. Raman-scattering spectroscopy of epitaxial graphene formed on SiC film on Si substrate 査読有り

    Yu Miyamoto, Hiroyuki Handa, Eiji Saito, Atsushi Konno, Yuzuru Narita, Maki Suemitsu, Hirokazu Fukidome, Takashi Ito, Kanji Yasui, Hideki Nakazawa, Tetsuo Endoh

    e-Journal of Surface Science and Nanotechnology 7 107-109 2009年1月10日

    DOI: 10.1380/ejssnt.2009.107  

    ISSN:1348-0391

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    By conducting a, 1200°C vacuum annealing of a 3C-SiC(111) ultrathin film preformed on a Si(110) surface, we have succeeded in forming a, graphene layer on a, Si substrate. Raman-scattering spectrum from this surface presents a distinct 2D band, whose deconvolution into four subcomponents indicates that the film mostly consists of a two-layer graphene. The peak position is blue-shifted from that of a free-standing graphene formed by a © 2009 The Surface Science Society of Japan.

  57. Erratum: Raman-Scattering Spectroscopy of Epitaxial Graphene Formed on SiC Film on Si Substrate [e-J. Surf. Sci. Nanotech. Vol. 7, pp. 107-109 (2009)]

    Miyamoto Yu, Handa Hiroyuki, Saito Eiji, Konno Atsushi, Narita Yuzuru, Suemitsu Maki, Fukidome Hirokazu, Ito Takashi, Yasui Kanji, Nakazawa Hideki, Endoh Tetsuo

    e-Journal of Surface Science and Nanotechnology 7 699-699 2009年

    出版者・発行元:The Surface Science Society of Japan

    DOI: 10.1380/ejssnt.2009.699  

    ISSN:1348-0391

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    In this article [Y. Miyamoto, et al., e-J. Surf. Sci. Nanotech. 7, 107 (2009)], we discussed formation of graphene on Si substrates assuming that the pre-grown 3C-SiC films on the Si(110) substrate are (111)-oriented. Later investigations suggest, however, that the 3C-SiC films used in this study are dominated by (110)- oriented portion, with the (111)-orientation being the minority. The comments on the (111)-orientation of the 3C-SiC films should therefore be omitted. This revision, however, does not affect our observation of graphene formation on Si substrates and the analyses thereon.[DOI: 10.1380/ejssnt.2009.699]

  58. 「酸素還元反応」の本質を探る-電気化学その場ラマン分光法を用いたアプローチ- 招待有り 査読有り

    伊藤隆

    化学と工業 62 (3) 258-259 2009年

  59. Mechanical and Tribological Properties of Boron, Nitrogen-Coincorporated Diamond-Like Carbon Films Prepared by Reactive Radio-Frequency Magnetron Sputtering 査読有り

    H. Nakazawa, A. Sudoh, M. Suemitsu, K. Yasui, T. Itoh, T. Endoh, Y. Narita, M. Mashita

    20th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, and Nitrides (Diamond 2009) 6-10 2009年

  60. Thin-Film Deposition of Silicon-Incorporated Diamond-Like Carbon by Plasma-Enhanced Chemical Vapor Deposition Using Monomethylsilane as a Silicon Source 査読有り

    Hideki Nakazawa, Yuhki Asai, Takeshi Kinoshita, Maki Suemitsu, Toshimi Abe, Kanji Yasui, Takashi Itoh, Tetsuo Endoh, Yuzuru Narita, Atsushi Konno, Yoshiharu Enta, Masao Mashita

    JAPANESE JOURNAL OF APPLIED PHYSICS 47 (11) 8491-8497 2008年11月

    出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS

    DOI: 10.1143/JJAP.47.8491  

    ISSN:0021-4922

    eISSN:1347-4065

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    We have deposited Si-incorporated diamond-like carbon (DLC) films by radio-frequency plasma-enhanced chemical vapor deposition using methane, argon, and monomethylsilane (MMS: CH(3)SiH(3)) as a silicon source, and have investigated the structural and mechanical properties of the films. The deposition rate and Si atomic fraction [Si/(Si + C) in the DLC films increased with increasing MMS flow ratio. The Si fraction was approximately 13% at a MMS flow ratio [MMS/(MMS + CH(4))] of 3%, showing that the deposition using a combination of CH(4) and MMS produces films with high Si content compared with those deposited using conventional C and Si sources. The Si fraction was also found to increase with a decrease in Ar flow rate under a constant MMS flow ratio. Many particles composed mainly of Si, whose size was 0.3-1 mu m in diameter, were observed on the surface when deposition was carried out at MMS flow ratios of 15 and 30%. Compressive internal stress in the films decreased with the MMS flow ratio and/or with the Ar flow rate. The decrease in internal stress is probably due to the relaxation of a three-dimensional rigid network by the formation of Si-C and Si-H bonds in the films are well as Ar(+) ion bombardment. [DOI: 10.1143/JJAP.47.8491]

  61. レーザーアブレーション法によるSi添加DLC膜の原子状水素エッチング 査読有り

    中澤日出樹, 杉田寛臣, 遠田義晴, 末光眞希, 安井寛治, 伊藤 隆, 遠藤哲郎, 成田 克, 真下正夫

    第22回 ダイヤモンドシンポジウム 2008年10月22日

  62. 第6回化学イノベーションシンポジウム”明日を開く科学のとびら”と杜の都の夏 招待有り 査読有り

    伊藤隆, 板谷謹悟

    化学と工業 61 (7) 732 2008年7月4日

  63. "Temperature oscillation" as a real-time monitoring of the growth of 3C-SiC on Si substrate 査読有り

    Eiji Saito, Atsushi Konno, Takashi Ito, Kanji Yasui, Hideki Nakazawa, Tetsuo Endoh, Yuzuru Narita, Maki Suemitsu

    APPLIED SURFACE SCIENCE 254 (19) 6235-6237 2008年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apsusc.2008.02.190  

    ISSN:0169-4332

    eISSN:1873-5584

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    Pyrometric interferometry has been observed during gas-source molecular beam epitaxy (GSMBE) of 3C-SiC on Si substrate using monomethyl silane. The period of the "temperature oscillation'' is shown to correspond to lambda/2n, with the lambda and n being the wavelength used in the monochromatic optical pyrometry and the refractive index of the grown film, respectively. As is the case for other heteroepitaxies, pyrometric interferometry may provide a feasible real-time monitoring method for the growth of 3C-SiC film on Si substrates. (C) 2008 Elsevier B.V. All rights reserved.

  64. メッシュ状金属キャタライザを用いたGaN結晶のエピタキシャル成長 招待有り 査読有り

    安井寛治, 末光眞希, 遠藤哲郎, 伊藤隆, 中澤日出樹, 成田克, 高田雅介, 赤羽正志

    第5回Cat-CVD研究会 2008年6月20日

  65. Hot-mesh CVD法を用いた原料ガスパルス供給によるGaN成長 査読有り

    小前泰彰, 齋藤健, 末光眞希, 遠藤哲郎, 伊藤隆, 中澤日出樹, 成田克, 高田雅介, 赤羽正志, 安井寛治

    第5回Cat-CVD研究会 2008年6月20日

  66. 触媒反応CVD (Cat-CVD) 法によるGaN結晶膜の省資源成長技術 査読有り

    安井寛治, 深田祐介, 安部和貴, 黒木雄一郎, 末光眞希, 伊藤 隆, 成田 克, 遠藤哲郎, 中澤日出樹, 高田雅介, 赤羽正志

    電子情報通信学会2008年総合大会 エレクトロニクス講演論文集2 (C-6-8) 26-27 2008年3月20日

    出版者・発行元:一般社団法人電子情報通信学会

  67. Epitaxial growth of SiC on Silicon on Insulator substrates with ultrathin top Si layer using hot-mesh chemical vapor deposition 査読有り

    Yusuke Fukada, Kanji Yasui, Yuichiro Kuroki, Maki Suemitsu, Takashi Ito, Tetsuo Endoh, Hideki Nakazawa, Yuzuru Narita, Masasuke Takata, Tadashi Akahane

    Jpn.J.Appl.Phys 47 (1) 669-672 2008年1月22日

    出版者・発行元:Jpn.J.Appl.Phys

    DOI: 10.1143/JJAP.47.569  

  68. Growth of GaN on SiC/Si substrates using AlN buffer layer by hot-mesh CVD 査読有り

    Kazuyuki Tamura, Yuichiro Kuroki, Kanji Yasui, Maki Suemitsu, Takashi Ito, Tetsuro Endou, Hideki Nakazawa, Yuzuru Narita, Masasuke Takata, Tadashi Akahane

    THIN SOLID FILMS 516 (5) 659-662 2008年1月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.tsf.2007.06.200  

    ISSN:0040-6090

    eISSN:1879-2731

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    GaN films were grown on SiC/Si (111) substrates by hot-mesh chemical vapor deposition (CVD) using ammonia (NH3) and trimetylgallium (TMG) under low V/III source gas ratio (NH3/TMG=80). The SiC layer was grown by a carbonization process on the Si substrates using propane or (C3H8). The AlN layer was deposited as a buffer layer using NH3 and trimetylaluminum (TMA). GaN films were formed and grown by the reaction between NHx radicals, generated on a tungsten hot mesh, and the TMG molecules. The GaN films with the AlN buffer layer showed L better crystallinity and stronger near-band-edge emission compared to those without the AlN layer. (C) 2007 Elsevier B.V. All rights reserved.

  69. Growth of GaN films by hot-mesh chemical vapor deposition using ruthenium-coated tungsten mesh 査読有り

    Yusuke Fukada, Kanji Yasui, Yuichiro Kuroki, Maki Suemitsu, Takashi Ito, Tetsuro Endou, Hideki Nakazawa, Yuzuru Narita, Masasuke Takata, Tadashi Akahane

    JAPANESE JOURNAL OF APPLIED PHYSICS 47 (1) 573-576 2008年1月

    出版者・発行元:JAPAN SOC APPLIED PHYSICS

    DOI: 10.1143/JJAP.47.573  

    ISSN:0021-4922

    詳細を見る 詳細を閉じる

    GaN films were grown on AIN/SiC/Si substrates by hot-mesh chemical vapor deposition (CVD) using ruthenium (Ru)-coated tungsten (W)-mesh. When using the Ru-coated mesh, the crystallinity of the GaN films did not degrade until a mesh temperature of 1000 degrees C, while the crystallinity markedly degraded at lower than 1100 degrees C when using the W-mesh. From the photoluminescence (PL) spectra of GaN films grown using the Ru-coated W-mesh, strong near-band-edge emission without yellow luminescence can be observed. In order to elucidate the difference in the decomposition efficiency of ammonia gas, the hydrogen radical density generated by the heated W-mesh and Ru-coated mesh was also evaluated using tungsten phosphate glass plates.

  70. ホットメッシュCVD法によるGaN成長-ルテニウムタングステンメッシュの効果- 査読有り

    深田祐介, 安部和貴, 黒木雄一郎, 末光眞希, 伊藤 隆, 成田 克, 遠藤哲郎, 中澤日出樹, 高田雅介, 安井寛治, 赤羽正志

    電子情報通信学会技術研究報告 (電子部品・材料研究会) 107 (325) 55-58 2007年11月16日

  71. Ru コートWを用いた Hot-mesh CVD法によるGaN膜成長 査読有り

    深田祐介, 小前泰彰, 黒木雄一郎, 末光眞希, 伊藤隆, 成田克, 遠藤哲郎, 中澤日出樹, 高田雅介, 安井寛治, 赤羽正志

    電子情報通信学会2007ソサイエティ大会 エレクトロニクス講演論文集2 (C-6-9) 17 2007年9月11日

    ISSN:1349-1369

  72. ルテニウム担持したタングステンHot-mesh CVD法によるGaN成長 査読有り

    深田祐介, 小前泰彰, 黒木雄一郎, 末光眞希, 伊藤 隆, 成田克, 遠藤哲郎, 中澤日出樹, 高田雅介, 安井寛治, 赤羽正志

    第4回Cat-CVD研究会 53-56 2007年6月29日

  73. In situ Raman spectroelectrochemistry of azobenzene monolayers on glassy carbon 招待有り 査読有り

    Takashi Itoh, Richard L. McCreery

    ANALYTICAL AND BIOANALYTICAL CHEMISTRY 388 (1) 131-134 2007年5月

    出版者・発行元:SPRINGER HEIDELBERG

    DOI: 10.1007/s00216-007-1192-4  

    ISSN:1618-2642

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    In situ Raman spectra of chemisorbed azobenzene (AB) monolayers on glassy carbon (GC) electrodes were observed under potentiostatic conditions in acetonitrile (ACN) with tetrabutyl-ammonium tetrafluoroborate (TBA-BF4). The Raman intensities of these spectra were high below -1000 mV, and this is attributed to the change in absorbance of AB on GC. In this paper, we describe chemisorbed AB molecules on GC electrode surfaces under potentiostatic conditions.

  74. 50.Effects of Threshold Voltage Fluctuations on Stability of MOS Current Mode Logic Inverter Circuit 査読有り

    Kazuhiro Suzuki, Hyoung-jun Na, Yuzuru Narita, Hideki, Nakazawa, Takashi Itoh, Kanji Yasui, Maki Suemitsu, Tetsuo Endoh

    IEEE, IMFEDK2007 technical digest B-7 2007年4月

  75. Electrochemical investigations of Al-carbon hybrid bipolar plate materials for polymer electrolyte fuel cells 査読有り

    Dongzhu Yin, Takashi Itoh, Kazumasa Toki, Atsuo Kasuya, Muneyoshi Yamada, Tatsuo Uchida

    ELECTROCHEMISTRY 75 (2) 187-189 2007年2月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    DOI: 10.5796/electrochemistry.75.187  

    ISSN:1344-3542

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    We have investigated new Al-carbon bipolar plate materials for a polymer electrolyte fuel cell (PEFC). Recently, many developments for bipolar plate materials have been founded in PEFC studies. More improvements are required in advancements for low corrosion rate, high conductivity and reduced cost. We propose a new concept for bipolar plate materials, specifically Al-carbon hybrid materials. This hybrid includes thin film carbon technology and ordered interfacial technology. The Al-carbon hybrid materials proposed in this paper have low corrosion rate, high conductivity and low cost. We present the electrochemical and physical properties of Al-carbon hybrid bipolar plate materials for PEFC. The corrosion behavior of At-carbon hybrid materials was investigated using the Tafel-extrapolation method and inductively coupled plasma spectrometry (ICP). In spite of local battery-effect reactions occurring within some At alloy materials, the proposed Al-carbon hybrid bipolar plate materials have good performance for corrosion resistance and conductivity.

  76. ホットメッシュCVD法によるGaN成長---ルテニウムコーティッドタングステンメッシュの効果 査読有り

    深田祐介, 安部和貴, 黒木雄一郎, 末光眞希, 伊藤 隆, 成田 克, 遠藤哲郎, 中澤日出樹, 高田雅介, 安井寛治, 赤羽正志

    信学技報 107 (325) 55-58 2007年

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

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    窒化ガリウム(GaN)は、wide-bandgap半導体で短波長、高温で動作する光デバイスとして用いられている。我々はこれまで、メッシュ状のタングステン(W)を用いたHot-mesh CVD法によりAlN/SiC/Si上へGaN膜を成長を試みてきた。得られた膜はWメッシュ温度1200℃において良好な結晶性、光学特性を示した。今回、さらにメッシュ温度の低温化を目指し、RuをコートしたWメッシュを用いてGaN成長を試みた。その結果、RuコートしたWメッシュを用いることで、1100℃以下の低温成長において結晶性や光学特性が改善した。

  77. Hydrogen-controlled crystallinity of 3C-SiC film on Si(001) grown with monomethylsilane 査読有り

    Yuzuru Narita, Atsushi Konno, Hideki Nakazawa, Takashi Itoh, Kanji Yasui, Tetsuo Endoh, Maki Suemitsu

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 46 (1-3) L40-L42 2007年1月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.46.L40  

    ISSN:0021-4922

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    Heteroepitaxial growth of 3C-SiC has been conducted on Si(001) substrate using monomethylsilane as a single source gas. By evaluating the crystalliniy of the film as a function of the growth temperature T and pressure P, a process window for a good epitaxy has been obtained, which is expressed as P-cl (T) &lt; P &lt; P-c2(T). Both of the two critical pressures increase with T, and are both successfully expressed with a single analytical function derived from the hydrogen adsorption/desorption balance on the surface.

  78. Characterization of Pt-based transition metal alloy electrodes for PEFC 査読有り

    M. Uebayashi, Y. Sawada, Y. Sato, T. Itoh, B. Jeyadevan, K. Tohji

    WATER DYNAMICS 898 162-+ 2007年

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.2721271  

    ISSN:0094-243X

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    Pt metal is generally used as electrocatalyst in polymer electrolyte fuel cells (PEFC). However, the catalytic action of Pt anode is obstructed by the adsorption of CO gas molecules on to their surface and consequently the efficiency of the fuel cell decreases. Moreover, the activity of PEFC deteriorates even if the presence of CO is as low as 100 ppm [1]. In this paper, attempts are being made to replace the Pt with Pt-based transition metal alloys such as PtFe and PtCo to overcome the above problem and also to improve the activity of fuel cells. The PtFe/C and PtCo/C necessary for the preparation of the electrodes were synthesized by depositing PtFe and PtCo particles synthesized using the polyol process on to the surface ketjenblack [2]. From the results of cyclic voltammetry, we could confirm that PtFe/C could be used as an alternate material of Pt/C. However, Fe ions get eluted in the electrolyte. Thus, the study that can control the elution of Fe ion is necessary. Also in case of PtCo/C, we could confirm that Co ion doesn't get to elute, however the hydrogen oxidation reaction current is quite low.

  79. その場赤外・ラマン分光法による電極表面解析 査読有り

    伊藤 隆

    表面科学 27 (10) 591-594 2006年10月1日

    DOI: 10.1380/jsssj.27.591  

  80. Phase transformation of unpromoted and promoted Fe catalysts and the formation of carbonaceous compounds during Fischer-Tropsch synthesis reaction 招待有り 査読有り

    Wensheng Ning, Naoto Koizumi, Hai Chang, Takehisa Mochizuki, Takashi Itoh, Muneyoshi Yamada

    APPLIED CATALYSIS A-GENERAL 312 35-44 2006年9月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apcata.2006.06.025  

    ISSN:0926-860X

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    Precipitated Fe catalysts with or without additives (Zn, K, Cu) were prepared, pretreated by CO, and then time-dependent behaviors of their FTS activities were investigated at 503 K and 1.6 MPa in a fixed bed reactor. Over the catalyst without additives, CO conversion showed a maximum at ca. 8 h on stream and then decreased monotonically with increasing time on stream. When Zn, K and/or Cu were added, respectively, similar behaviors were observed. However, an increasing CO conversion was observed during on stream (29 h) when Zn, K and Cu were added simultaneously. X-ray diffraction (XRD) analysis of these catalysts showed the formation of Fe carbides (Fe5C2 and FexC) after the CO pretreatment irrespective of the catalyst composition. In the case of the catalyst without additives, these carbides were oxidized to Fe3O4 during on stream. The oxidation of the carbides was more significant on the catalyst charged near the outlet of the reactor. For the catalyst containing all the additives simultaneously, however, the Fe carbides were only phases detected by XRD analysis even after the long time on stream (29 h). In addition, the formation of amorphous carbonaceous compounds was observed by laser Raman spectroscopy (LRS) for the catalysts after the CO pretreatment and/or the FTS reaction. So-called a graphite-like carbonaceous compound was not observed by LRS, which was considered as one of reasons for the catalyst deactivation in the previous studies. Therefore, it is suggested that the oxidation of the Fe carbides by H2O vapor is a main reason for the deactivation of the Fe FTS catalyst. Because the Zn, K and Cu containing catalyst showed a higher CO2 selectivity, the combination of these additives improves the water-gas shift activity, thereby suppresses the oxidation of the Fe carbides. (C) 2006 Elsevier B.V. All rights reserved.

  81. 燃料電池が作る未来 招待有り 査読有り

    伊藤 隆

    まなびの杜 35 6-6 2006年3月31日

  82. Deactivation mechanism of NiMo catalyst during the ultra deep hydrodesulfurization of gas oil: Characterization of the spent catalysts by means of temperature programmed oxidation and laser desorption/ionization-time of flight mass spectroscopy

    Naoto Koizumi, Yoshihisa Urabe, Hikotaro Suzuki, Takashi Itoh, Muneyoshi Yamada

    ACS National Meeting Book of Abstracts 232 2006年

    ISSN:0065-7727

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    The present study has characterized the spent NiMo catalysts used for the ultra deep HDS of gas oil in commercial plants for ca. 2 years by means of temperature programmed oxidation and laser desorption/ionization-time of flight mass spectroscopy, in order to make clear its deactivation mechanism under commercial operations. The deposition of carbonaceous compounds was observed by these techniques on all the spent catalysts examined here. Furthermore, their molecular structure and chemical nature (combustive property) strongly depended on the catalyst position in the HDS reactor, where more refractory carbonaceous compound with condensed aromatic structures was observed only on the spent catalysts charged near the outlet of the HDS reactor. Considering the residual HDS activity of the spent catalysts, we proposed that the deposition of such the refractory carbonaceous compound on the catalysts causes the (entire) catalyst deactivation during the ultra deep HDS of gas oil, especially at the beginning of on stream.

  83. Low-temperature heteroepitaxial growth of 3C-SiC(111) on Si(110) substrate using monomethylsilane 査読有り

    Atsushi Konno, Yuzuru Narita, Takashi Ito, Kanji Yasui, Hideki Nakazawa, Tetsuo Endoh, Maki Suemitsu

    ECS Transactions 3 (5) 449-455 2006年

    DOI: 10.1149/1.2357236  

    ISSN:1938-5862 1938-6737

    eISSN:1938-6737

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    Heteroepitaxial growth of 3C-SiC on Si(110) substrate has been successfully conducted at T=1000°C by using monomethylsilane as a single source gas. X-ray diffraction (XRD) reveals that the growth orientation of the film is rotated and a 3C-SiC(111) film is formed on this Si(110) substrate. The film quality, as evaluated with the half width of the XRD rocking curve, shows improvement from that of 3C-SiC(111)/Si(111) film. The lattice constant anisotropy (a∥-a⊥)/a∥ between the lateral and the growth directions also decreased by a factor of four from that of 3C-SiC(111)/Si(111), and the two lattice constants approach to that of bulk SC-SiC. These results indicate significant reduction in the strain of the 3C-SiC film in this 3C-SiC(111)/Si(110) system. XRD φ-scan indicates presence of double domains with almost equal areas. Copyright The Electrochemical Society.

  84. In situ surface-enhanced Raman scattering spectroelectrochemistry of oxygen species 招待有り 査読有り

    T Itoh, T Maeda, A Kasuya

    FARADAY DISCUSSIONS 132 95-109 2006年

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/b506197k  

    ISSN:1364-5498

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    In situ surface-enhanced Raman scattering (SERS) combined with electrochemical analysis is applied to the determination of oxygen species on silver electrodes in alkaline hydroxide aqueous solution at room temperature and gold electrodes in carbonate melts at high temperature. This technique, referred to as SERS spectroelectrochemistry, reveals Raman spectral lines in the 500 - 1100 cm(-1) range under electrode potential scanning, assignable to superoxide ions (O-2(-)) and peroxide ions (O-2(2-)) on the electrode surface. These lines for oxygen molecule species have potential dependence with changing potential. In the alkaline hydroxide aqueous solution, the Raman peaks due to oxygen molecules are observed at potentials between 0.2 V and - 0.8 V ( vs. Ag/AgCl) only in the cathodic scan. This irreversible behavior in cyclic voltammograms indicates the existence of an intermediate stage in the oxygen reduction process, in which oxygen is released from the AgO films on the electrode at potentials corresponding to the onset of the last current peak in the voltammogram. This liberated oxygen molecule remains in solution at the interface until hydroxyls or water molecules are formed when the potential reaches the potential zero charge (PZC). In the high-temperature carbonate melts, Raman lines at 1047, 1080, and 800 cm(-1) are apparent for the eutectic ( 62 + 38) mol% (Li + K) CO3 melt at 923 K, and at 735 cm(-1) for the Li2CO3 melt at 1123 K. These results suggest that oxygen reduction in the Li2CO3 melt involves only peroxide ions, while that in ( 62 + 38) mol% ( Li + K) CO3 involves both peroxide and superoxide ions at the three-phase boundary interface.

  85. Synthesis of new electron-doped cuprates LixSr2CuO2X2 (X = Cl, Br) 招待有り 査読有り

    T Kajita, M Kato, T Suzuki, T Itoh, T Noji, Y Koike

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 426 500-504 2005年10月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.physc.2005.01.039  

    ISSN:0921-4534

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    We have successfully synthesized new electron-doped cuprates LixSr2CuO2Cl2 with x &lt;= 0.10 and LixSr2CuO2Br2 with x &lt;= 0.34 using an electrochemical Li-intercalation technique. The electrochemical Li-intercalation has been carried out at room temperature under a constant potential of 500 mV vs. Li/Li+ using a three-electrode cell set up as LixSr2CuO2X2 (X = Cl, Br)vertical bar 1.0 M LiClO4/PC vertical bar Li. A sheet of Li was used as a reference electrode also. The magnetic susceptibility measurements have revealed the appearance of superconductivity in LixSr2CuO2Br2. The superconducting transition temperature, T-c, is 8 K and independent of the Li-content x, while the superconducting volume fraction at 2 K exhibits the maximum at x similar to 0.15. In addition, no superconductivity has been observed in LixSr2CuO2Cl2. (c) 2005 Elsevier B.V. All rights reserved.

  86. Investigation of carbonaceous compounds deposited on NiMo catalyst used for ultra-deep hydrodesulfurization of gas oil by means of temperature-programmed oxidation and Raman spectroscopy 査読有り

    N Koizumi, Y Urabe, K Inamura, T Itoh, M Yamada

    CATALYSIS TODAY 106 (1-4) 211-218 2005年10月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.cattod.2005.07.172  

    ISSN:0920-5861

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    NiMo/Al(2)O(3) catalyst used for ultra-deep]ADS of several gas oils at various conditions was characterized by both temperature-programmed oxidation combined with mass spectroscopy (TPO-MS) and/or gas chromatography (TPO-GC), and Raman spectroscopy to make clear how the catalyst was deactivated. TPO-MS showed the presence of carbonaceous compounds containing H and N atoms on the used catalysts. TPO-GC showed that the combustive property of the carbonaceous compounds sensitively changes depending on the HDS reaction conditions and the position of the catalyst charged in the HDS reactor. A curve fitting analysis of TPO-GC profiles indicated that the carbonaceous compounds combusted below 680 K during TPO were observed on all the spent catalysts examined here whereas more refractory carbonaceous compound (combusted at around 690 K during TPO) was observed on the catalyst that had experienced severe HDS reaction conditions. More refractory carbonaceous compound was preferentially observed on the catalyst charged near the outlet of the HDS reactor. Raman spectra of the carbonaceous compounds indicated that the carbonaceous compounds combusted below 680 K during TPO has an amorphous-like structure whereas the refractory carbonaceous compound has a graphite-like one. Raman spectra also indicated that the graphite-like carbonaccous compound possesses a greater lateral size than the amorphous-like one, implying that the refractory carbonaceous compound can cover the catalyst surface more effectively. The carbonaceous compound having a graphite-like structure is one of main reasons for the catalyst deactivation. It is suggested that the precursor for this type of carbonaceous compound is not formed directly from the feed, but indirectly formed during the HDS of gas oil, because of its preferential deposition on the catalyst charged near the outlet of the HDS reactor. (c) 2005 Elsevier B.V. All rights reserved.

  87. 固体高分子型燃料電池が作るエネルギー社会 招待有り 査読有り

    伊藤 隆, 望月剛久

    表面科学 2005 (6) 362-366 2005年6月1日

    出版者・発行元:The Surface Science Society of Japan

    DOI: 10.1380/jsssj.26.362  

    ISSN:0388-5321

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    Polymer Electrolyte Fuel Cells (PEFCs) are one of the possible energy sources for the near future energy systems. The advantages of PEFC power generation are one of the most effective energy conversion systems and gentle in our environment. In addition, PEFC attracts huge interests as power supply systems for portable electric devices, residential power generation systems and electric vehicles. This article introduces here the comparison of several different types of Fuel Cells, their mechanisms and up-to-date research and developing stages for PEFC.

  88. Photoelectrochemical oxygen evolution using polysulfide as sacrificial electron acceptor 査読有り

    G Milczarek, A Kasuya, K Tohji, T Arai, T Ito

    SOLAR ENERGY MATERIALS AND SOLAR CELLS 86 (1) 43-52 2005年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.solmat.2004.06.004  

    ISSN:0927-0248

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    A two-compartment photoelectrochemical cell consisting of a TiO2 photoanode, Nafion membrane and platinized tin oxide glass as the cathode was constructed. The anolyte and catholyte were 1 M NaOH and 1 M Na2S4, respectively. Illumination of the photoanode resulted in oxygen evolution in the anodic compartment simultaneously with the reduction of tetrasulfide in the cathodic compartment. The mechanism of such a photoelectrochemical oxygen evolution is discussed throughout and the possible application of this reaction in solar water splitting is mentioned. (C) 2004 Elsevier B.V. All rights reserved.

  89. New electron-doped superconducting cuprate LixSr2CuO2Br2 査読有り

    T Kajita, M Kato, T Suzuki, T Itoh, T Noji, Y Koike

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (11B) L1480-L1481 2004年11月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.43.L1480  

    ISSN:0021-4922

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    A new electron-doped superconductor LixSr2CuO2Br2 with x = 0.15 has successfully been synthesized by an electrochemical Li-intercalation technique. The magnetic susceptibility shows superconductivity of bulk with the superconducting transition temperature T-c = 8 K. This compound is the first electron-doped superconducting cuprate with the K2NiF4 structure.

  90. Raman spectro-electrochemistry of LiCoxMn2-xO4 thin film electrodes for 5 V lithium batteries 査読有り

    K Dokko, N Anzue, M Mohamedi, T Itoh, Uchida, I

    ELECTROCHEMISTRY COMMUNICATIONS 6 (4) 384-388 2004年4月

    出版者・発行元:ELSEVIER SCIENCE INC

    DOI: 10.1016/j.elecom.2004.02.005  

    ISSN:1388-2481

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    Raman spectra of thin films of LiCoxMn2-xO4 (0 &lt; x &lt; 1) were recorded in a mixture of ethylene carbonate and dimethyl carbonate (1:1 by volume) containing 1 M LiBF4 at electrode potentials of 3.5-5.5 V. The thin film electrodes were fabricated on gold substrates by electrostatic spray deposition (ESD). The in situ Raman spectra exhibited changes correlatable with the crystallographic structure and oxidation state of manganese and cobalt. The spectral changes were reversible by changing the electrode potential, indicating that lithium ion extraction and insertion proceeds in a reversible manner. (C) 2004 Elsevier B.V. All rights reserved.

  91. In situ Raman spectroelectrochemistry of oxygen species on gold electrodes in high temperature molten carbonate melts 査読有り

    T Itoh, K Abe, K Dokko, M Mohamedi, Uchida, I, A Kasuya

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 151 (12) A2042-A2046 2004年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1812735  

    ISSN:0013-4651

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    In order to clarify the reaction mechanisms for oxygen reduction related to superoxide and peroxide ions in molten carbonates, we have attempted to obtain in situ Raman spectra on a gold electrode by a surface-enhanced Raman scattering technique at the three-phase boundary under potentiostatic conditions. In situ experiments were carried out with a gold electrode in molten (62 + 38) mol% (Li + K) CO3 eutectic at 923 K and in molten Li2CO3 at 1123 K. Raman lines at 1047, 1080, and 800 cm(-1) appeared for the (62 + 38) mol% (Li + K) CO3, and at 735 cm(-1) for the Li2CO3 single melt. These Raman lines are assigned to the stretching vibration of superoxide ions (1047 and 1080 cm(-1)), and peroxide ions (800 and 735 cm(-1)). These oxide species may be associated with the oxygen reduction at the three-phase boundary interface. The results suggest the oxygen reduction in a Li2CO3 melt involves peroxide ions, while the reduction in a (62 + 38) mol% (Li + K) CO3 melt involves both peroxide and superoxide ions. (C) 2004 The Electrochemical Society.

  92. Impedance spectroscopic characterization of polymer lithium-ion battery at elevated temperatures in accelerated rate calorimeter (ARC) 査読有り

    H Ishikawa, M Mohamedi, T Itoh, Uchida, I

    ELECTROCHEMISTRY 71 (12) 1030-1032 2003年12月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:1344-3542

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    In this work, we present a set of thermal characterization experiments of charged prismatic polymer lithium-ion battery (PLB). Cells at different state of charge (SOC) were tested inside an accelerated rate calorimeter (ARC) to determine the onset-of-thermal runaway (OTR) temperatures, and the thermally activated components were followed by monitoring the impedance (at 1 kHz) and the open circuit voltage (OCV) as a function of temperatures. An increase in the impedance was observed at around 133 degreesC corresponding to the polyethylene separator shutdown. Above 140 degreesC, the OCV dropped to zero indicating an internal short-circuit due to the separator meltdown, suggesting that the pinholes created in the separator at meltdown were large enough to create an internal short circuit. In addition, electrochemical impedance spectroscopy (EIS) at some SOCs was performed in the frequency range of 10 kHz-0.1 Hz at various temperatures (25-13 degreesC). Results were modeled using an appropriate equivalent circuit, and parameters that affected the battery behavior at high temperatures would be identified.

  93. Fabrication of thin film electrodes of LiMxMn2-xO4 (M = Ni, Co) for 5 volt lithium batteries 査読有り

    K Dokko, N Anzue, Y Makino, M Mohamedi, T Itoh, M Umeda, Uchida, I

    ELECTROCHEMISTRY 71 (12) 1061-1063 2003年12月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:1344-3542

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    By means of an electrostatic spray deposition technique, thin-films (0.5 mum thick) of LiMxMn2-xO4 (M = Ni, Co) were fabricated on gold substrates. The prepared thin-films had a spinel-related structure. Cyclic voltammetry (CV) measurements were performed in a potential range of 3.4-5.5 V vs. Li/Li+. Both LiNixMn2-xO4 and LiCoxMn2-xO4 exhibited reversible CV peaks at higher than 4.5 V. LiNixMn2-xO4 showed two peaks at 4.7 V, and those corresponded to the redox of Ni2+/4+ in the spinel structure, while the redox of Mn3+/4+ took place at 4 V. Similarly, LiCoxMn2-xO4 displayed current responses at 5 V due to the redox of Co3+/4+.

  94. In situ assessment of LiMn2O4 degradation during prolonged exposure in carbonate-based electrolytes 査読有り

    M Mohamedi, N Anzue, K Dokko, T Itoh, Uchida, I

    ELECTROCHEMISTRY 71 (12) 1168-1171 2003年12月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:1344-3542

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    The degradations of thin-film LiMn2O4 electrodes during prolonged exposure to 1 M LiPF6/EC-DMC at room temperature and 55degreesC, were assessed by in situ Raman spectroscopy. Our results demonstrate that different deterioration mechanisms of the spinel were found depending on the temperature. Exposure of a thin-film spinel LiMn2O4 electrode to LiPF6/EC-DMC electrolyte at room temperature and WC led to spontaneous formation of a thin insulating surface layer. This process is accompanied by the transformation of the LiMn2O4 electrode surface into lambda-MnO2 and Mn2O3 at room temperature and 55degreesC, respectively.

  95. Influence of oxygen on luminescence and vibrational spectra of Mg-doped GaN 査読有り

    Y Koide, DE Walker, BD White, LJ Brillson, T Itoh, RL McCreery, M Murakami, S Kamiyama, H Amano, Akasaki, I

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH 240 (2) 356-359 2003年11月

    出版者・発行元:WILEY-V C H VERLAG GMBH

    DOI: 10.1002/pssb.200303279  

    ISSN:0370-1972

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    Mg-doped GaN epilayers are analyzed by Raman and low-energy electron-excited nanoluminescence (LEEN) spectroscopies before and after oxygen ambient annealing at temperatures from 450 to 550 degreesC. Annealing as low as 450 degreesC shows the appearance of a local vibrational mode of the Mg-Ga acceptor. Correspondingly, LEEN emission at 2.8 eV increases and that at 3.27 eV decreases after annealing in oxygen ambient. On the other hand, electron beam treatment decreases 2.8 eV emission and increases 3.27 eV emission. These luminescence properties are explained by a donor-acceptor pairs transition model due to hydrogen-related deep and shallow donors and MgGa acceptor. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  96. Temperature effect on methanol and ethanol electrooxidation at Pt/C and Pt-Ru/C microporous electrodes 査読有り

    CG Lee, T Itoh, M Mohamedi, M Umeda, Uchida, I, HC Lima

    ELECTROCHEMISTRY 71 (7) 549-554 2003年7月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:1344-3542

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    Temperature effect on methanol and ethanol electrooxidation was investigated with cyclic voltammetry at carbon supported Pt and Pt-Ru microporous electrodes. In methanol solution, the currents were enhanced by 10 and 20 times at Pt/C and Pt-Ru/C, respectively in the temperature range from 25degreesC to 80degreesC. With increasing temperature at both electrodes, decreases in the potential difference of oxidation peaks at positive and negative potential scanning were observed, indicating that OH adsorption on the catalysts affects methanol oxidation and bifunctional mechanism is active. Especially, vertically increased oxidation peak during negative potential scanning was observed at Pt/C, presumably due to the weak OH adsorption on the platinum surface. The effect of ruthenium addition on the poisoning reduction was also confirmed. In ethanol solution, Pt/C increased currents only by a factor of 4 whereas Pt-Ru/C raised it about 8 times for the same temperature range. Lower temperature dependence of currents in the ethanol solution is probably caused by weaker OH adsorption in the ethanol solution than in the methanol solution. The ruthenium addition remarkably enhanced ethanol oxidation performance probably due to the strong adsorption of OH. In both alcohols, Pt-Ru/C showed larger apparent activation energies of oxidation than Pt/C, representing higher temperature dependence of OH adsorption on ruthenium.

  97. In situ Raman spectroscopic study of thin-film Li1-xMn2O4 electrodes 査読有り

    N Anzue, T Itoh, M Mohamedi, M Umeda, Uchida, I

    SOLID STATE IONICS 156 (3) 301-307 2003年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0167-2738(02)00693-8  

    ISSN:0167-2738

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    In order to investigate structural changes in lithium manganese oxide during the insertion and extraction of lithium ions, Raman spectra of thin films of Li1-xMn2O4 produced by electrostatic spray deposition (ESD) were recorded in situ during a voltammetric scan in 1 M LiClO4 in propylene carbonate (PD)/ethylene carbonate (EC) solutions. Five Raman-active bands, as predicted by the theory, were observed for the Li1-xMn2O4 compound. The X-MnO2 phase has a distinct band at 592 cm(-1) and therefore can be clearly recognized from Raman spectra. The changes observed in Raman lines of Li1-xMn2O4 were ascribed to the occurrence of the phase transition of Li1-xMn2O4 electrodes. From the energy-dependence of Raman spectra, it is suggested that each value of x in Li1-xMn2O4 possesses its own electronic band structure. (C) 2003 Elsevier Science B.V. All rights reserved.

  98. Porous micro-ring electrode - Preparation and investigation of methanol oxidation 査読有り

    Y Hatakeyama, M Umeda, M Mohamedi, T Itoh, Uchida, I

    ELECTROCHEMISTRY 70 (12) 964-965 2002年12月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:1344-3542

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    We have developed a porous micro-ring electrode, which conventionally represents a part of membrane electrode assembly (MEA) of proton exchange membrane (PEM) fuel cell. The porous micro-ring electrode has a PEM/electro-catalyst layered structure at a tip of a glass capillary. This electrode has proven to exhibit electrocatalytic properties. Moreover, the methanol oxidation reaction at the PEM/electrocatalyst could be measured and evaluated.

  99. Electrochemical investigation of LiNi0.5Mn1.5O4 thin film intercalation electrodes 査読有り

    M Mohamedi, A Makino, K Dokko, T Itoh, Uchida, I

    ELECTROCHIMICA ACTA 48 (1) 79-84 2002年11月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0013-4686(02)00554-6  

    ISSN:0013-4686

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    This work provides kinetic and transport parameters of Li-ion during its extraction/insertion into thin film LiNi0.5Mn1.5O4 free of binder and conductive additive. Thin films of LiNi0.5Mn1.5O4 (0.2 mum thick) were prepared on electronically conductive gold substrate utilizing the electrostatic spray deposition technique. High purity LiNi0.5Mn1.5O4 thin film electrodes were observed with cyclic voltammetry, to exhibit very sharp peaks, high reversibility, and absence of the 4 V signal related to the Mn3+/Mn4+ redox couple. The electrode subjected to 100 CV cycles of charge/discharge delivered a capacity of 155 mAh g(-1) on the first cycle and sustained a good cycling behavior while retaining 91% of the initial capacity after 50 cycles. Kinetics and mass-transport of Li-ion extraction at LiNi0.5Mn1.5O4 thin film electrode were investigated by means of electrochemical impedance spectroscopy. The apparent chemical diffusion coefficient (D-app) value determined from EIS measurements changed depending on the electrode potential in the range of 10(-10)-10(-12) cm(2) s(-1). The D-app profile shows two minimums at the potential values close to the peak potentials of the corresponding cyclic voltammogram. (C) 2002 Elsevier Science Ltd. All rights reserved.

  100. In situ Raman spectroelectrochemistry of electron transfer between glassy carbon and a chemisorbed nitroazobenzene monolayer 査読有り

    T Itoh, RL McCreery

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 124 (36) 10894-10902 2002年9月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/ja020398u  

    ISSN:0002-7863

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    In situ Raman spectroscopy was used to monitor 4-nitroazobenzene (NAB) in an electrochemical cell, both as a free molecule and as a chemisorbed monolayer on a glassy carbon (GC) electrode surface. Reduction of free NAB exhibited two well-defined voltammetric couples in acetonitrile, and the accompanying spectral changes supported a mechanism involving two successive 1-e(-) transfers. Raman spectra of NAB chemisorbed to GC via diazonium ion reduction were obtained in acetonitrile with a high-sensitivity, line-focused CCD spectrometer. The chemisorbed NAB spectra were quite different from the free NAB spectra, and were sufficiently strong to monitor as a function of applied potential. In the potential range of +400 to -800 mV vs Ag/Ag+, the intensity of the Raman bands associated with the phenyl-NO2 moiety varied, implying an electronic interaction between the T system of the graphitic substrate and the chemisorbed NAB molecules. Negative of -800 mV, a 1-e(-) voltammetric reduction peak was observed, which was reversible on the positive voltage scan. This peak was accompanied by significant spectral changes, particularly the loss of the N=N and NO2 stretches. The spectra are consistent with formation of a quinoid structure containing a C=C double bond between the NAB and the graphitic surface. The electron transfer and spectral changes occurred over a wider potential range than expected for a conventional Nernstian equilibrium, but did not appear to be broadened by slow electron-transfer kinetics. The results imply a significant perturbation of electron transfer between the GC and the monolayer, caused by strong electronic coupling between the graphitic pi, system and the NAB orbitals. Rather than a discrete electron transfer to a free molecule, the electron transfer to chemisorbed NAB is more gradual, and is presumably driven by the electric field at the electrode/solution interface.

  101. A mechanism for conductance switching in carbon-based molecular electronic junctions 査読有り

    AO Solak, S Ranganathan, T Itoh, RL McCreery

    ELECTROCHEMICAL AND SOLID STATE LETTERS 5 (8) E43-E46 2002年8月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1490716  

    ISSN:1099-0062

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    A molecular junction formed by a 10-15 Angstrom organic monolayer between carbon and mercury contacts exhibited conductance switching for several monolayer structures. When the carbon potential was scanned to a sufficiently negative voltage relative to the mercury, the junction resistance suddenly decreased by at least an order of magnitude, and high resistance could be restored by a positive voltage scan. The high and low conductance states were persistent, and conductance switching was repeatable at least 100 cycles for the case of a terphenyl junction. The switching behavior is consistent with phenyl ring rotation and formation of a planar, quinoid structure as a consequence of electron injection into the monolayer. A unique feature of the junction structure is the strong electronic coupling between the monolayer pi system and the graphitic carbon through a quinoid double bond. Not only does this interaction lead to high conductivity and possible practical applications as a molecular switch, it also combines the electronic properties of the conjugated monolayer with those of the graphitic substrate. The switching mechanism reported here is an example of "dry electrochemistry'' in which a redox process appears to occur under the influence of a high electric field in the absence of solvent or electrolyte. (C) 2002 The Electrochemical Society.

  102. Electrochemical stability of thin film LiMn2O4 cathode in organic electrolyte solutions with different compositions at 55 degrees C 査読有り

    M Mohamedi, D Takahashi, T Itoh, Uchida, I

    ELECTROCHIMICA ACTA 47 (21) 3483-3489 2002年8月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0013-4686(02)00285-2  

    ISSN:0013-4686

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    A survey of the electrochemical stability of electrostatic spray deposited thin film of LiMn2O4 was performed in LiClO4-EC-PC, LiBF4-EC-PC, and LiPF6-EC-PC solutions at 55 C. The solution resistance, the surface film resistance, and the charge-transfer resistance were all found to depend on the electrolyte composition. Among the LiX-salts studied, the lowest charge transfer-resistance, and surface layer resistance were obtained in LiBF4-EC-PC solution. There is no major influence of the electrolyte solution compositions upon lithium ion transport in the LiMn2O4 bulk at 55 degreesC. The diffusion coefficient of lithium in the solid phase varied within 10(-10)-10(-8) cm(2) s(-1) in the three solutions. In general, it seems that in LiBF4 solutions, the surface chemistry is the most stable in the three solutions examined, and hence the electrode impedance in LiBF4 solutions was the lowest. In LiPF6 solutions, HF seems to play an important role, and thus, the electrode impedance is relatively high due to the precipitation of surface LiF. (C) 2002 Elsevier Science Ltd. All rights reserved.

  103. Cyclic voltammetry and AC impedance of MmNi3.55Co0.75Mn0.4Al0.3 alloy single-particle electrode for rechargeable Ni/MH battery 査読有り

    M. Mohamedi, T. Sato, T. Itoh, M. Umeda, I. Uchida

    Journal of the Electrochemical Society 149 (8) A983-A987 2002年8月

    DOI: 10.1149/1.1488646  

    ISSN:0013-4651

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    Voltammetry and ac impedance techniques were run on a single particle of MmNi3.55Co0.75Mn0.4Al0.3 alloy electrode with the aim of refining the investigating of the kinetics of the hydrogen adsorption-absorption processes into mischmetal alloys. The experimental impedance spectra for the hydrogen adsorption/absorption are similar in shape and in accordance with the theoretical predictions. Data were analyzed using an equivalent circuit based on the knowledge of the different processes taking place in the metal hydride electrodes. The model fitted the experimental data remarkably well. The equivalent circuit considers the charge-transfer reaction, the hydrogen transition between the adsorbed and absorbed states, and the impedance of finite hydrogen diffusion into the metal hydride electrode particle with spherical symmetry. The values of the obtained diffusion coefficient of hydrogen in the solid phase were 8.7-9 × 10-8 cm2 s-1 for the hydrogenation and dehydrogenation processes, respectively.

  104. Impedance characterization of hydrogen adsorption-absorption into an Mg2Ni alloy single particle electrode 査読有り

    M Mohamedi, T Sato, T Itoh, M Umeda, Uchida, I

    JOURNAL OF NEW MATERIALS FOR ELECTROCHEMICAL SYSTEMS 5 (3) 197-202 2002年7月

    出版者・発行元:ECOLE POLYTECHNIQUE MONTREAL

    ISSN:1480-2422

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    Simple electroless solutions plating have been applied to Mg2Ni alloy: (i) Ni-plating solution using NiSO4 + NaPH2O2 + NaH2C6H5O7, (ii) a reducing solution using NaPH2O2 + NaH2C6H5O7, and (iii) acid solution consisting of CuSO4 + H2SO4. The electrochemical characteristics and performance of thus modified electrodes were examined using cyclic voltammetry, and electrochemical impedance spectroscopy techniques with the microelectrode technique focusing on a single particle of the alloy. The results show that all applied surface modifications have significantly improved the electrocatalytic activity of the Mg2Ni towards hydrogen absorption/adsorption processes compared to the untreated alloy. Among all the treated samples, the highest discharge capacity of 320 mAh/g, and the lowest charge-transfer resistance were obtained with Mg2Ni alloy treated by copper plating method.

  105. Microvoltammetric study of electrochemical properties of a single spherical nickel hydroxide particle 査読有り

    HS Kim, T Itoh, M Nishizawa, M Mohamedi, M Umeda, Uchida, I

    INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 27 (3) 295-300 2002年3月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0360-3199(01)00118-5  

    ISSN:0360-3199

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    Electrochemical studies of spherical nickel hydroxide Ni(OH)(2) with high density were carried out by using a microelectrode technique. A carbon fiber microelectrode was contacted with a single particle of nickel hydroxide in 5 M KOH aqueous solution. In this way, cyclic voltammetry and galvanostatic charge/discharge experiments were carried out. The Ni(OH)(2); NiOOH redox reaction, oxygen evolution reaction and charge/discharge capacity were examined without any dilution with a binder and a conductive additive. Data were compared with those of the composite electrode consisting of the nickel hydroxide particle and a polymer binder, which is the practical form in the Ni-MH batteries. The potential-step technique was also performed to evaluate the apparent chemical diffusion coefficient of the proton (D-app) in the nickel hydroxide. Since the nickel hydroxide particle was a dense, conductive sphere, the spherical diffusion model was employed for the analysis. The D-app was found to be around 10(-9) cm(2) s(-1). (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

  106. Rapid evaluation of charge/discharge properties for lithium manganese oxide particles at elevated temperatures 査読有り

    K Dokko, S Horikoshi, T Itoh, M Nishizawa, T Abe, M Umeda, Uchida, I

    JOURNAL OF SOLID STATE ELECTROCHEMISTRY 6 (3) 188-193 2002年3月

    出版者・発行元:SPRINGER-VERLAG

    DOI: 10.1007/s100080100216  

    ISSN:1432-8488

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    A microelectrode technique was applied to investigate the electrochemical properties of LiMn2O4 particles at elevated temperatures. Cyclic voltammograms of LiMn2O4 were measured after the particles were exposed to the electrolytes. This technique results in rapid and precise evaluation of the redox behavior of the materials. A significant capacity fading was observed in 1 M LiPF6/EC + PC electrolytic solution, which indicates that both LiMn2O4 and LiPF6 participate in the reaction to produce an inert material on the particle surface. Next, the capacity fading for two different BET surface area particles were compared using 1 M LiPF6/ EC+ PC at 50 degreesC. The reaction was found not to be controlled by the surface area. Finally, a Li1.1Mn1.9O4 particle was employed. The fading in discharge was ca. 10% for 50 cycles even at 50 degreesC, which means that the partial substitution of Mill in LiMn2O4 by Li substantially enhanced the capacity stability.

  107. ESD fabricated thin films of spinel LiMn2O4 for lithium microbatteries - I. Effects of thickness 査読有り

    M Mohamedi, D Takahashi, T Itoh, M Umeda, Uchida, I

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 149 (1) A19-A25 2002年1月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1424285  

    ISSN:0013-4651

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    Electrochemical properties of thin films of LiMn2O4 spinels of several thicknesses prepared by electrostatic spray deposition (ESD) were studied in 1 M LiClO4/propylene carbonate solution using cyclic voltammetry and electrochemical impedance spectroscopy. The shapes of the cyclic voltammograms (CVs) is extremely affected by the scan rate. In general, at a constant film thickness, the slower the scan rates the sharper and narrower are the peaks. A progressive decrease in the charge-transfer resistance was always found with raising the film thickness and the applied potential. Both the film thickness and the charge injection process effectively limit the region over which diffusion control is observed. The diffusion control domain shrinks with decreasing film thickness in agreement with the theoretical predictions. The diffusion coefficient of Li ions in the solid phase varied in a similar manner with the potential, irrespective of the film thickness. The diffusion coefficient exhibited a peak-shaped function of the electrode's potential with minima at potentials close to the peak potentials of the CV. Importantly, operating at a constant potential, the chemical diffusion coefficient decreases within the 1-0.5 mum range, and is almost constant for smaller thicknesses. (C) 2001 The Electrochemical Society.

  108. In situ Raman spectroscopic studies of LiNixMn2-xO4 thin film cathode materials for lithium ion secondary batteries 査読有り

    K Dokko, M Mohamedi, N Anzue, T Itoh, Uchida, I

    JOURNAL OF MATERIALS CHEMISTRY 12 (12) 3688-3693 2002年

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/b206764a  

    ISSN:0959-9428

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    Chemical states and structural changes accompanying the electrochemical Li extraction and insertion of LiNixMn2-xO4 (0 &lt; x &lt; 0.5) thin films in LiBF4-EC-DMC solutions, studied by in situ Raman spectroscopy, are reported for the first time. Ex situ Raman measurements for the virgin electrodes revealed that the oxidation state of Ni in the pristine thin films was Ni2+. In situ Raman spectra of the thin films collected in the organic electrolyte during Li ion extraction and insertion in the potential range 3.4-5.0 V vs. Li/Li+ showed a new Raman band at 540 cm(-1) appearing around 4.7 V, which is attributed to the Ni4+-O bond. In addition, from the in situ Raman spectral changes, it is suggested that Li ion extraction and insertion proceed as follows: the redox of Ni2+/3+ takes place in the potential range 4.4-4.7 V, and Ni3+/4+ in the 4.7-5.0 V range, while the redox at 3.8-4.4 V corresponds to Mn3+/(4+). Furthermore, it was confirmed that these changes in the Raman spectra were reversible upon changing the electrode potential, and the Li ion extraction and insertion proceed in a reversible manner.

  109. Explicit study on the oxidation mechanism of nickel in molten Li2CO3-K2CO3 査読有り

    M Mohamedi, Y Hisamitsu, T Kudo, T Itoh, Uchida, I

    JOURNAL OF SOLID STATE ELECTROCHEMISTRY 5 (7-8) 538-545 2001年10月

    出版者・発行元:SPRINGER-VERLAG

    DOI: 10.1007/s100080000180  

    ISSN:1432-8488

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    The oxidation behavior of nickel in Li + K carbonate melt is followed by measuring the open-circuit potential and by electrochemical impedance spectroscopy under an O-2 + CO2 gas mixture in the ratio 90/10 at a total pressure of 1 atm at 650 degreesC. X-ray diffraction (XRD) and energy-dispersive spectroscopy are employed for qualitative and quantitative analyses of the different compounds involved during the oxidation of nickel. Atomic force microscopy is used for both imaging the evolution of the oxide layer and determining its surface roughness. The in situ oxidation process of nickel demonstrates three stages: rapid formation of a compact surface oxide (first stage), thicker oxide layer (second stage), and a porous oxide structure (third stage). The lithiation reaction has been identified to occur during the second stage. Formation of an intermediate and unstable compound, namely NiCO3, has been confirmed by XRD.

  110. Xerographic and electroabsorption study of primary photocarrier generation process in x-form metal-free phthalocyanine 査読有り

    M Umeda, M Mohamedi, T Itoh, Uchida, I

    JOURNAL OF APPLIED PHYSICS 90 (8) 3984-3987 2001年10月

    出版者・発行元:AMER INST PHYSICS

    DOI: 10.1063/1.1403674  

    ISSN:0021-8979

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    Using a dual-layered photoconductor, we have investigated the primary photocarrier generation process in x-form metal-free phthalocyanine (x-H2PC) over a wide range of illumination wavelengths. According to the results of quantum efficiency measurements, it has been established that the photocarrier generation mechanism in x-H2PC occurs via two processes: (i) production of an intermediate that depends solely on the excitation energy, and (ii) subsequent free carrier production in the presence of an electric field. In addition, the spectral quantum efficiency and the electroabsorption spectrum were measured and compared. Based on that, the primary process efficiency was divided into four regions in terms of photon energy, which explained well the relationship between them. The excitation energy dependence of the primary efficiency was semiquantitatively validated based on the electron transfer theory. (C) 2001 American Institute of Physics.

  111. Methanol gas sensing using ultramicroelectrodes: studies on sensing mechanism and its enhancement 査読有り

    M Umeda, A Kabasawa, M Kokubo, M Mohamedi, T Itoh, Uchida, I

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 40 (8) 5141-5144 2001年8月

    出版者・発行元:INST PURE APPLIED PHYSICS

    DOI: 10.1143/JJAP.40.5141  

    ISSN:0021-4922

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    Electrochemical detection of methanol vapor has been achieved using a highly sensitive small detector by an ultramicroelectrode-based electrochemical method. First, a peak cur-rent was observed by employing potential sweep voltammetry at a microring ring electrode. The current peak was confirmed to be that of the methanol vapor. Next, (i) the potential-sweep rate dependence of the peak current at the microring ring electrode, and (ii) the electrode-gap width dependence of the cyclic voltammogram at the microgap electrode were measured. Based on the results, the electrochemical-detection mechanism of vapor methanol has been proposed. Finally, an enhancement method for detecting methanol vapor was achieved by the proposed mechanism. Namely, using a Nafion (R) -membrane-coated dualmicroelectrode we succeeded in detecting the methanol vapor by approximately 200 times higher than that by the bare electrode at an applied voltage of 4V.

  112. In situ SERS spectroscopy of Ag-modified pyrolytic graphite in organic electrolytes 査読有り

    T Itoh, K Abe, M Mohamedi, M Nishizawa, Uchida, I

    JOURNAL OF SOLID STATE ELECTROCHEMISTRY 5 (5) 328-333 2001年7月

    出版者・発行元:SPRINGER-VERLAG

    DOI: 10.1007/s100080000139  

    ISSN:1432-8488

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    Surface enhanced Raman scattering (SERS) has been applied to study the lithium intercalation/deintercalation process at the interface of a pyrolytic graphite electrode with propylene and ethylene carbonate containing organic solutions. We have focused on the lattice vibration of the most outer graphite surface layer simultaneously with cyclic voltammetric measurements. In situ Raman spectroscopy performed in this way allowed us to determine the La value that describes the size of graphitic microcrystallites along the a-axis. It was found that the La value decreases when the electrode is polarized to potentials between 0.02 and 1.0 V. This phenomenon can be correlated with the intercalation of lithium ions into the graphene structure. According to the spectral change, the size of the graphitic microcrystallites shows reversible behavior with potential cycling at the surface of the electrode.

  113. Recent investigations on thin films and single particles of transition metal oxides for lithium batteries 査読有り

    Uchida, I, M Mohamedi, K Dokko, M Nishizawa, T Itoh, M Umeda

    JOURNAL OF POWER SOURCES 97-8 518-524 2001年7月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0378-7753(01)00724-8  

    ISSN:0378-7753

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    Various aspects in the lithium battery field have been explored in our group: (i) uniform and dense thin films of LiMn2O4, up to 0.5 mum thickness have been synthesized by electrostatic spray deposition (ESD). The electrochemical properties of these films were investigated by cyclic voltammetry and impedance spectroscopy under a variety of experimental conditions. (ii) The kinetic and transport properties of Lithium insertion/extraction of numerous sphere-shaped single particles have been also evaluated by transient techniques as well as by ac-impedance spectroscopy. (iii) Electrochemical quartz crystal microbalance (EQCM) technique was employed to study the low capacity fading of LiMn2O4 at elevated temperatures in LiPF6 containing solutions. It has been confirmed that this phenomenon is due to the manganese dissolution promoted by acidic species (HF) originated from the reaction of LiPF6 with water. (iv) Alternative materials were sought to replace the actual LiCoO2 or LiMn2O4. Among them: Li1.1Mn1.9O4. LiNi0.85Co0.15O2, and Li,Li1.10Mn1.852Cr0.048O4. Interestingly, Li1.10Mn1.852Cr0.048O4 exhibited no significant capacity fading even in the 1 M LiPF6/PC-EC (1:1) solution at 50 degreesC upon 50 cycles of charge/discharge. (C) 2001 Elsevier Science B.V. All rights reserved.

  114. Gas phase hydrogen electrooxidation using an integrated ultramicroelectrode 査読有り

    M Umeda, K Dokko, M Mohamedi, T Itoh, Uchida, I

    CHEMISTRY LETTERS (6) 508-509 2001年6月

    出版者・発行元:CHEMICAL SOC JAPAN

    DOI: 10.1246/cl.2001.508  

    ISSN:0366-7022

    eISSN:1348-0715

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    We have demonstrated a hydrogen electrooxidation in the gas phase by employing a Nafion-coated integrated ultramicroelectrode, which represents the three-phase interface of a membrane assembled electrode for a polymer electrolyte fuel cell. The limiting current of gas-phase hydrogen oxidation is proven to be more than ten times larger than that in hydrogen saturated water.

  115. Kinetic characterization of single particles of LiCoO2 by AC impedance and potential step methods 査読有り

    K Dokko, M Mohamedi, Y Fujita, T Itoh, M Nishizawa, M Umeda, Uchida, I

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 148 (5) A422-A426 2001年5月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1359197  

    ISSN:0013-4651

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    This is the first report of impedance technique run on single particle LiCoO2 electrodes with the aim of clarifying its electronic and ionic transport properties. Measurements were successfully conducted on a LiCoO2 particle of 15 mum diam resulting in impedance magnitude on the order of M Omega. The impedance spectra exhibited (i) one semicircle in the high frequency region, (ii) Warburg impedance in low frequencies, and finally, (iii) a limiting capacitance in the very low frequencies. The spectra were analyzed using a modified Randles-Ershler circuit, so that the reaction kinetics could be precisely evaluated. The charge transfer resistance decreased as the potential increased, whereas the double layer capacitance was almost invariant with the potential. Thus, the apparent chemical diffusion coefficient (D-app) of lithium ions was determined to be 10(-11) to 10(-7) cm(2)/s as function of electrode potential. These results are in agreement with those obtained by potential step chronoamperometry technique. (C) 2001 The Electrochemical Society.

  116. Explicit analysis of impedance spectra related to thin films of spinel LiMn2O4 査読有り

    M Mohamedi, D Takahashi, T Uchiyama, T Itoh, M Nishizawa, Uchida, I

    JOURNAL OF POWER SOURCES 93 (1-2) 93-103 2001年2月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0378-7753(00)00551-6  

    ISSN:0378-7753

    eISSN:1873-2755

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    A uniform, dense film of spinel LiMn2O4 (0.1 mum thick) has been prepared by the electrostatic spray deposition (ESD) technique. The electroanalytical behavior of this electrode is elucidated by application of electrochemical impedance spectroscopy (EIS). The data have been modeled using an equivalent circuit approach. An excellent fit was found between measured data and an equivalent circuit, comprising Li+ migration through surface him, potential-dependent charge transfer resistance, semiinfinite Warburg-type element, reflecting solid state Li+ ion diffusion and a finite space Warburg-type element, describing both diffusion and accumulation of lithium at the very low frequency. The apparent chemical diffusion coefficient of lithium in the spinel phase was found within 10(-12) &lt; &lt;(D)over tilde&gt;(Li) &lt; 10(-9) cm(2) s(-1) as a function of electrode potential with minima at the potentials corresponding to the voltammetric peaks. The intercalation capacitance was found 0.7 &lt; C-L &lt; 47 mF cm(-2) exhibiting maxima at the potentials corresponding to the voltammetric peaks. (C) 2001 Elsevier Science B.V. All rights reserved.

  117. Ni-Al alloy as alternative cathode for molten carbonate fuel cells 査読有り

    M Mohamedi, Y Hisamitsu, K Kihara, T Kudo, T Itoh, Uchida, I

    JOURNAL OF ALLOYS AND COMPOUNDS 315 (1-2) 224-233 2001年2月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0925-8388(00)01278-0  

    ISSN:0925-8388

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    The in situ oxidation of Ni-5at.%Al and Ni-15at.%Al alloys in Li+K carbonate melt were investigated by measuring open-circuit potential and electrochemical impedance spectroscopy under an O-2 + CO2 gas mixture in the ratio 90:10 at a total pressure of 1 atm at 650 degreesC. In situ oxidation processes of Ni-Al alloys demonstrate three stages. The period of the oxidation process depends on the aluminum content in the alloy. The final product has probably a multilayer structure. Where the inner part is compact (probably also multilayer in nature) and the outer part (solution side) is porous. Ni-5at.% Al electrode exhibited excellent stability during one-week; immersion in the carbonate melt. Extension of cathode lifetime in molten carbonate fuel cells (MCFC) appears possible if the Ni cathode is modified by the addition of small concentration of aluminum. (C) 2001 Elsevier Science B.V. All rights reserved.

  118. Solubility of NiO as cathode material for MCFC in alkali carbonate melts 査読有り

    M Mohamedi, Q Yu, K Kihara, Y Hisamitsu, T Kudo, T Itoh, M Umeda, Uchida, I, Selman, JR

    PROCEEDINGS OF THE 6TH INTERNATIONAL SYMPOSIUM ON MOLTEN SALT CHEMISTRY AND TECHNOLOGY 6 (2001) 235-240 2001年

    出版者・発行元:SHANGHAI UNIV

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    An optimized alkali carbonate composition of 47.4 mol% Li2CO3/32.6 mol% Na2CO3/20 mol% K2CO3 is proposed for molten carbonate fuel cells. This composition was obtained by considering both the oxygen solubility and the electrolytic conductivity in various electrolyte compositions. Solubility measurements of NiO in this composition is also reported and compared with these in Li/K and Li/Na carbonate melts under atmospheric O-2/CO2=90/10 or O-2/CO2=20/80 gas mixtures. It has been found that under O-2/CO2=90/10 NiO has almost the same solubility in all melts. On the other hand under O-2/CO2=20/80, the 70 mol% Li2CO3/30 mol% Na2CO3 melt exhibits the lowest NiO solubility. If the electric conductivity were the only factor determining cell performance, also the 70 mol% Li2CO3/30 mol% Na2CO3 melt would be selected as the electrolyte of choice for MCFC. On the condition that oxygen solubility, electrolytic conductivity, and NiO solubility were to be considered, the 47.4 mol% Li2CO3/32.6 mol% Na2CO3/20 mol% K2CO3 ternary melt would be the best candidate for MCFC.

  119. Amorphous tin oxide films: preparation and characterization as an anode active material for lithium ion batteries 査読有り

    M Mohamedi, SJ Lee, D Takahashi, M Nishizawa, T Itoh, Uchida, I

    ELECTROCHIMICA ACTA 46 (8) 1161-1168 2001年1月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/S0013-4686(00)00702-7  

    ISSN:0013-4686

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    Tin oxide thin films were prepared by the electrostatic spray deposition at 400 degreesC, followed by annealing at 500 degreesC in air. X-ray diffraction and X-ray photoelectron spectroscopy revealed that the resulting films were amorphous SnO2. The electrochemical properties of the SnO2 films with lithium were studied by in situ conductivity measurements using an interdigitated microarray electrode as well as by cyclic voltammetry, galvanostatic cycling measurements and ac-impedance spectroscopy in 1 M LiClO4/(PC + EC). The SnO2 film electrodes exhibited reversible capacities greater than 1300 mA h g(-1) when cycled between 0.05 and 2.5 V at 0.2 mA cm(-2). However, this capacity faded rapidly after repeated cycling. If the electrode was cycled between 0 and 1.0 V, a reversible capacity of 600 mA h g(-1) was maintained for more than 100 cycles. In addition, a stable reversible capacity of about 500 mA h g(-1) was obtained even at current density as high as 2 mA cm(-2). Thus it is suggested that a higher potential than 1.5 V would cause reformation of tin oxide, which may destroy the stable nanocomposite structure of metallic tin and lithium. These arguments were supported by in situ conductivity measurements with microarray electrodes. (C) 2001 Elsevier Science Ltd. All rights reserved.

  120. Effect of molten carbonate composition on oxygen reduction under pressurized conditions: cyclic voltammetry and equivalent circuit analysis 査読有り

    M Mohamedi, Y Hisamitsu, Y Ono, T Itoh, Uchida, I

    JOURNAL OF APPLIED ELECTROCHEMISTRY 30 (12) 1397-1404 2000年12月

    出版者・発行元:KLUWER ACADEMIC PUBL

    DOI: 10.1023/A:1026539032082  

    ISSN:0021-891X

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    The oxygen reduction mechanism was investigated in carbonate melts of variable composition ranging from the eutectics Li-K, Li-Na to ternary Li-Na-K melts. The effect of pressure on electrode kinetics was also examined. Cyclic voltammetry, convolution voltammetry and electrochemical impedance spectroscopy have shown that oxygen reduction is mass-transfer limited in all melt compositions investigated. It was also found that pressurizing increased the concentration of oxygen electroactive species. To gain information about the reaction mechanism, the impedance spectra have been fitted to four possible equivalents circuits: (i) Randles circuit, (ii) Randles circuit extended by a parallel RC circuit due to film formation, (iii) Gerisher (homogeneous reaction) impedance, and (iv) Modified Randles circuit. The discussion of the results is based on careful analysis of fit quality and meaningfulness of fit parameters.

  121. Spectroelectrochemical studies on highly polarized LiCoO2 electrode in organic solutions 査読有り

    T Itoh, N Anzue, M Mohamedi, Y Hisamitsu, M Umeda, Uchida, I

    ELECTROCHEMISTRY COMMUNICATIONS 2 (11) 743-748 2000年11月

    出版者・発行元:ELSEVIER SCIENCE INC

    DOI: 10.1016/S1388-2481(00)00112-0  

    ISSN:1388-2481

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    In situ Raman spectroscopy was conducted on thin film electrodes of pure LiCoO2 in order to observe the nature of the changes in interfacial structure between LiCoO2 and organic solutions (propylene carbonate and ethylene carbonate containing 1 M LiClO4) when LiCoO2 is scanned up to highly anodic potentials (similar to 5.0VLi(+)/Li). Raman spectra and cyclic voltammograms were recorded simultaneously during the potential scan. We observed a sudden increase in the background signals of the Raman spectra at potentials more positive than 4.7 V. The increased background did not change after potential cycling. The change was irreversible, indicating that surface film formation occurred at positive potentials. As organic compounds fluoresce by visible light, the increased background is ascribed to the formation of a film On the LiCoO2 electrode surface in organic solutions. (C) 2000 Published by Elsevier Science S.A.

  122. Microvoltammetry of lithium nickel oxide single particle: deterioration of the redox behavior by water molecules 査読有り

    K Dokko, M Umeda, T Itoh, Uchida, I

    ELECTROCHEMISTRY COMMUNICATIONS 2 (10) 717-719 2000年10月

    出版者・発行元:ELSEVIER SCIENCE INC

    DOI: 10.1016/S1388-2481(00)00110-7  

    ISSN:1388-2481

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    The microelectrode technique was applied to investigate the electrochemical behavior of LiNiO2 which seriously influenced by water molecules. Cyclic voltammograms of humidified LiNiO2 particles were compared to that of as-synthesized. As a result, a significant peak-potential shift was observed, which denotes that the reaction product caused by H2O generates an electrochemical inactive material on the particle which prevents the Li+ insertion/extraction. The reaction product was considered to be NiO, and deterioration property has also been discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

  123. Microvoltammetry for cathode materials at elevated temperatures: electrochemical stability of single particles 査読有り

    K Dokko, S Horikoshi, T Itoh, M Nishizawa, M Mohamedi, Uchida, I

    JOURNAL OF POWER SOURCES 90 (1) 109-115 2000年9月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0378-7753(00)00456-0  

    ISSN:0378-7753

    eISSN:1873-2755

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    The electrochemical stability of single particles of cathode materials (LiMn2O4, Li1.10Cr0.048Mn1.852O4, LiCoO2 and LiNi0.85Co0.15O2) was investigated by means of a microelectrode technique at 25 degrees C and 50 degrees C. The cycle stability was evaluated by multi-cyclic voltammetry. LiMn2O4 showed good cycle stability in LiClO4/propylene carbonate (PC) + ethylene carbonate (EC) and LiBF4/PC + EC solutions even at 50 degrees C. On the contrary, in LiPF6/PC + EC, significant capacity fading during charge-discharge was observed at 50 degrees C. The cycle stability of LiMn2O4 in the latter solution was improved by partial substitution of Mn by Cr and Li. Regarding LiCoO2, its cycle life in LiClO4/PC + EC at 50 degrees C was unsatisfactory when the potential was scanned between 3.60 and 4.30 V. On the other hand, LiCoO2 retained 90% of its capacity when the potential scan was limited to 4.00 V. LiNi0.85Co0.15O2 showed similar trend at 50 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.

  124. Electric-field dependent redox electron transfer in an organic solid: study of carrier photogeneration efficiency 査読有り

    M Umeda, M Nishizawa, T Itoh, Selman, JR, Uchida, I

    CHEMICAL PHYSICS LETTERS 326 (3-4) 219-224 2000年8月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0009-2614(00)00766-1  

    ISSN:0009-2614

    eISSN:1873-4448

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    We have investigated the electric field dependence of the carrier photogeneration efficiency in an organic photoconductor with high sensitivity. The rate-determining step to generate photocarriers was considered to be the electron transfer between the neighboring two-redox molecules, which is influenced by the electric field. The overall carrier photogeneration efficiency was expressed by employing the electron-transfer velocity at the rate-determining step as a function of electric-field-dependent activation energy. This model successfully fits the experimental results for an organic photoconductor over a wide range of field strengths. (C) 2000 Published by Elsevier Science B.V.

  125. Electrochemical quartz crystal microbalance investigations of LiMn2O4 thin films at elevated temperatures 査読有り

    T Uchiyama, M Nishizawa, T Itoh, Uchida, I

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 147 (6) 2057-2060 2000年6月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1393485  

    ISSN:0013-4651

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    Electrochemical properties of a LiMn2O4 Blm in 1 M LIPF6/PC + EC solution was studied by means of the electrochemical quartz crystal microbalance (QCM) at an elevated temperature (50 degrees C). The film preparation was conducted by an electrostatic spray deposition, which enabled us to obtain a uniform and dense film of LiMn2O4 on a QCM electrode at low temperature (400 degrees C) to avoid the thermal damage of the quartz. During the galvanostatic charge-discharge experiment, the mass of electrode specimen increased, most likely due to the formation of a passivation film. If an as-prepared electrode was only immersed in the LiPF6 solution at 50 degrees C, the mass of electrode decreased steadily, resulting eventually in extinction of the manganese film. Such manganese dissolution was attended by a shift of open circuit voltage from 3.8 to 4.3 V vs. Li, suggesting a formation:for lambda-MnO2 as an intermediate in the dissolution reaction. (C) 2000 The Electrochemical Society. S0013-4651(99)09-053-9. All rights reserved.

  126. Electrochemical in-situ conductivity measurements for thin film of Li1-xMn2O4 spinel 査読有り

    M Nishizawa, T Ise, H Koshika, T Itoh, Uchida, I

    CHEMISTRY OF MATERIALS 12 (5) 1367-1371 2000年5月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/cm990696z  

    ISSN:0897-4756

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    Electrical conductivity of LiMn2O4, which is a promising cathode active material for lithium ion batteries, was monitored in situ during electrochemical lithium extraction and reinsertion reactions in 1 M LiClO4 propylene carbonate solution. The in-situ conductivity measurement was achieved by means of an interdigitated microarray electrode coated with a uniform and dense film of LiMn2O4 The conductivity of Li1-xMn2O4 was found to exhibit a peak-shaped profile as a function of lithium content. The conductivity of Cr3+-doped spinel, LiMn1.95-Cr0.05O4, decreased monotonically with decreasing lithium content. These results are discussed by considering the effects of phase transformation on the conductivity of these materials.

  127. In situ observation of LiNiO2 single-particle fracture during Li-ion extraction and insertion 査読有り

    K Dokko, M Nishizawa, S Horikoshi, T Itoh, M Mohamedi, Uchida, I

    ELECTROCHEMICAL AND SOLID STATE LETTERS 3 (3) 125-127 2000年3月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1390977  

    ISSN:1099-0062

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    Electrochemical lithium-ion extraction/insertion properties of Li1-xNiO2 single particles were investigated by attaching a filament microelectrode to the particle in 1 mol/dm(3) LiClO4/ethylene carbonate + propylene carbonate electrolyte. High-resolution cyclic voltammograms and galvanostatic chronopotentiograms were recorded. In addition, we observed in situ particle fracture during charge-discharge using an optical microscope equipped with a charge-coupled device camera. We found that the particle fractures when it is polarized above 4.2 V vs. Li/Li+. This phenomenon was explained by the change in crystal parameters expected to occur for x &gt; 0.75 in Li1-xNiO2. (C) 2000 The Electrochemical Society. S1099-0062(99)11-042-3. All rights reserved.

  128. High-Speed voltammetry of Mn-doped LiCoO2 using a microelectrode technique 査読有り

    S Waki, K Dokko, T Itoh, M Nishizawa, T Abe, Uchida, I

    JOURNAL OF SOLID STATE ELECTROCHEMISTRY 4 (4) 205-209 2000年3月

    出版者・発行元:SPRINGER VERLAG

    DOI: 10.1007/s100080050196  

    ISSN:1432-8488

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    The microelectrode technique was applied to investigate the electrochemical properties of LiCo1-xMnxO2 (x = 0, 0.01, 0.05, 0.2, or 0.5) synthesized using the citrate process. From the X-ray diffraction measurements, an expansion of the c-axis and a decrease in the crystal size of the materials were observed on substitution of Mn into LiCoO2 In the electrochemical measurements, the high-speed cyclic voltammogram for the Mn-substituted materials gave one set of peaks at 3.9 V vs. Li/Li+. The apparent chemical diffusion constant (D-app) of LiCo0.8Mn0.2O2 obtained from the potential step experiment was 6.4 x 10(-8) cm(2)/s, which is larger than that of LiCoO2. The increase in D-app is attributable to the expansion of the c-axis and/or the decrease in the crystal size. In addition, the increase in Mn substitution up to 20% lead to an improvement in the kinetic reversibility and the cycle stability of LiCoO2.

  129. Influence of adsorption phenomena upon the mechanism and kinetics of oxygen reduction at a gold electrode in (Li-Na)CO3 melt 査読有り

    M Mohamedi, Y Hisamitsu, Y Ono, T Itoh, Uchida, I

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 147 (2) 490-495 2000年2月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.1393222  

    ISSN:0013-4651

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    The reduction of oxygen at a gold flag electrode fully immersed in (53 + 47) mol % (Li-Na)CO3 was investigated at different temperatures (600 similar to 750 degrees C) using cyclic voltammetry and the semi-integral method. It was found that the electrode reaction mechanism depends critically on the scan rate and temperature. The overall mechanism is complicated by adsorption phenomena. This was identified via semi-integral analysis by the appearance of a peak-shaped semi-integrated voltammetric response. An electron transfer number equal to 2 was determined by the simultaneous use of the voltammetric peak and the maximum value of the semi-integral curve. Both the initial surface excess, Gamma*, and the mass-transfer parameter CD1/2 could be determined from the semi-integration of a single voltammogram. (C) 2000 The Electrochemical Society. S0013-4651(99)06-048-6 All rights reserved.

  130. EQCM investigations of LiMn2O4 thin films at elevated temperatures 査読有り

    T Uchiyama, M Nishizawa, T Itoh, Uchida, I

    INTERCALATION COMPOUNDS FOR BATTERY MATERIALS, PROCEEDINGS 99 (24) 160-173 2000年

    出版者・発行元:ELECTROCHEMICAL SOCIETY INC

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    Electrochemical properties of a LiMn2O4 film in 1M LiPF6 / PC+EC solution was studied by means of the electrochemical quartz crystal microbalance (EQCM) at an elevated temperature (50 degrees C). The film preparation was conducted by an electrostatic spray deposition (ESD), which enables us to obtain a uniform and dense film of LiMn2O4 onto a QCM electrode at low temperature (400 degrees C) to avoid the thermal damage of the quartz. During the galvanostatic charge-discharge experiment, the mass of electrode specimen increased probably due to the formation of a passivation film. If an as-prepared electrode was just immersed in the LiPF6 solution at 50 degrees C, the mass of electrode decreased steadily, resulting eventually In extinction of the manganese film. Such manganese dissolution was attended by a shift of open circuit voltage from 3.8V to 4.3V vs. Li, suggesting a formation of lambda-MnO2 as an intermediate in the dissolution reaction.

  131. Chronoamperometric studies of LiCoO2 and LiNiO2 particles during lithium-ion insertion/extraction

    K Dokko, S Horikoshi, M Nishizawa, T Itoh, T Abe, Uchida, I

    LITHIUM BATTERIES, PROCEEDINGS 99 (25) 290-297 2000年

    出版者・発行元:ELECTROCHEMICAL SOCIETY INC

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    Lithium-ion insertion/extraction kinetics at a single particle of transition metal oxides (LiCoO2 and LiNiO2) were investigated with microelectrode technique, in which a fine metal filament was manipulated to make an electric contact with a single particle placed in an electrolyte solution. The apparent chemical diffusion coefficient (D-app) of lithium ion was determined by potential-step chronoamperograms assuming spherical diffusion in the particle. It was found that the diffusion rate of lithium ions within these layered oxides increases with the expansion of interlayer distance. In addition to such general tendency, the plots of D-app showed minimum values at the two-phase reaction regions.

  132. High temperature in situ Raman spectroscopy of oxide species in molten (Li + K) carbonate eutectic 査読有り

    T Itoh, K Abe, Y Hisamitsu, M Mohamedi, M Nishizawa, T Abe, P Tomczyk, Uchida, I

    CHEMISTRY LETTERS (10) 1115-1116 1999年10月

    出版者・発行元:CHEMICAL SOC JAPAN

    DOI: 10.1246/cl.1999.1115  

    ISSN:0366-7022

    eISSN:1348-0715

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    In situ Raman spectra of active oxygen species present in solutions of potassium superoxide (KO2) in (62 + 38) mol% (Li + K)(2)CO3 eutectic at 650 degrees C were observed. We have attempted to obtain vibrational spectra of these entities by surface enhanced Raman scattering (SERS) technique.

  133. In situ conductance measurement to investigate roles of conductive additives in lithium ion battery electrodes 査読有り

    M Nishizawa, H Koshika, T Itoh, M Mohamedi, T Abe, Uchida, I

    ELECTROCHEMISTRY COMMUNICATIONS 1 (9) 375-378 1999年9月

    出版者・発行元:ELSEVIER SCIENCE INC

    ISSN:1388-2481

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    Electrical de conductance of a composite electrode for a lithium-ion battery was monitored in situ during successive charge/discharge cycles, in order to investigate functions of conductive additives. Such measurement was achieved by means of an interdigitated microarray electrode with a bipotentiostat. The composite films of mesocarbon microbeads ( MCMBs) heat-treated at 1000 degrees C were studied with conductive additives of acetylene black or a synthetic graphite in a 1 M LiClO4, non-aqueous carbonate solution. The role of the conductive additives is discussed in connection with their type and content within the composites. In addition, we propose a modified preparation procedure for the composites having a high retention of conductance. (C) 1999 Elsevier Science S.A. All rights reserved.

  134. Electrochemical quartz crystal microbalance for insertion/extraction of lithium in spinel LiMn2O4 thin films 査読有り

    M Nishizawa, T Uchiyama, T Itoh, T Abe, Uchida, I

    LANGMUIR 15 (15) 4949-4951 1999年7月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/la990270z  

    ISSN:0743-7463

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    The electrochemical quartz crystal microbalance (EQCM) technique was successfully used to investigate the lithium insertion/extraction reaction in LiMn2O4 spinel. A uniform and dense film of LiMn2O4 was prepared by electrostatic spray deposition (ESD) onto an Au-coated quartz plate, which was used as an electrode for the EQCM experiments. The ESD method enabled us to perform the low-temperature spinel synthesis at 400 degrees C td avoid the thermal damage of the quartz. The electrochemical properties of the LiMn2O4 film in a 1 M LiClO4 carbonate solution were studied at 50 degrees C. The data obtained for the lithium insertion/extraction were discussed for the first time in connection with the mass change of the LiMn2O4 specimen.

  135. Microvoltammetric study of electrochemical hydrogenation of a surface-treated Mg2Ni alloy single particle 査読有り

    HS Kim, M Nisizawa, T Itoh, Uchida, I

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 72 (7) 1643-1646 1999年7月

    出版者・発行元:CHEMICAL SOC JAPAN

    DOI: 10.1246/bcsj.72.1643  

    ISSN:0009-2673

    eISSN:1348-0634

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    The effects of surface treatments on the hydrogen storage properties of a Mg2Ni alloy particle were investigated by the microvoltammetric technique, in which a carbon-filament microelectrode was manipulated to make electrical contact with the particle placed in a KOH aqueous solution. It was found that the hydrogen storage properties of Mg2Ni at room temperature were improved by the surface treatments with a nickel plating solution. The sodium salts (sodium phosphinate and sodium dihydrogen citrate) contained in the nickel plating solution made the alloy form an amorphous-like state, resulting in an improved hydrogen absorption/desorption capacity at room temperature as high as about 150 mA hg(-1) from the original value of 17 mA hg(-1).

  136. Ion- and electron-transport properties of a single particle of disordered carbon during the lithium insertion reaction 査読有り

    M Nishizawa, H Koshika, R Hashitani, T Itoh, T Abe, Uchida, I

    JOURNAL OF PHYSICAL CHEMISTRY B 103 (24) 4933-4936 1999年6月

    出版者・発行元:AMER CHEMICAL SOC

    DOI: 10.1021/jp990604t  

    ISSN:1089-5647

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    The electrical de conductance (S) and the solid-state diffusion coefficient of the lithium ion (D-Li(+)) were evaluated for a single spherical particle of mesocarbon microbead (MCMB) heat-treated at 1000 degrees C. The measurements were conducted in situ during the electrochemical lithium insertion into the MCMB by using microelectrode-based techniques. The data obtained are discussed as functions of the electrode potential and of the amount of inserted lithium. Both parameters (S and D-Li(+)) were found to depend on the lithium content, and their variation manner changed around 0.6 V vs Li/Li+ at which the inserted lithium amount was ca. 25% of the total insertion. The results would arise from the difference between the first and the second half of the lithium insertion reaction mechanisms.

  137. Convolution voltammetry applied for the diagnosis of adsorption phenomena during the oxygen reduction in alkali carbonate eutectic 査読有り

    M Mohamedi, Y Hisamitsu, Y Ono, T Itoh, Uchida, I

    CARBONATE FUEL CELL TECHNOLOGY 99 (20) 242-252 1999年

    出版者・発行元:ELECTROCHEMICAL SOCIETY INC

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    Adsorption process during the reduction of oxygen was investigated at different temperatures (600 similar to 750 degrees C) at a gold flag electrode fully immersed in the (53+47)mol%(Li-Na)CO3. Detection of adsorption was achieved by means of semiintegration of the experimental current in voltammetry. The electron number equal to 2 was determined by the simultaneous use of the voltammetric peak and the maximum value of the semiintegral curve. Both the surface excess, Gamma(*), and the mass-transfer parameter C*D-1/2 could be determined from the semiintegration of a single voltammogram.

  138. Cathodic performance of in situ oxidized Ni+Al alloys in molten Li plus Na carbonate eutectic 査読有り

    Y Hisamitsu, Y Ono, M Mohamedi, T Itoh, T Kudo, P Tomczyk, Uchida, I

    CARBONATE FUEL CELL TECHNOLOGY 99 (20) 337-346 1999年

    出版者・発行元:ELECTROCHEMICAL SOCIETY INC

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    The present work describes the electrochemical behavior of in situ oxidized (0.95Ni + 0.05Al) and (0.85Ni + 0.15Al) alloys for the oxygen reduction in (Li+Na)carbonate eutectic. Thin films of Ni+Al alloys were prepared on gold substrates by a sputtering method and subjected to in situ oxidation in the melt at 923K. Voltammetric behavior of the oxides is compared with that of the non-alloyed Ni to show that Ni+Al alloys with low content of Al are electrochemically active for the oxygen reduction and stable in the melt, Additionally it has been shown that the fractal approach can be successfully applied to simulate the rough surfaces of (Ni/Au) and (Ni+Al/Au) electrodes in molten carbonates. On the basis of data obtained this way, higher stability of oxide film at the (Ni+Al/Au) electrodes in comparison to NiO electrodes has been demonstrated.

  139. In situ Raman spectroscopic investigations of oxide chemistry in molten carbonates 査読有り

    T Itoh, K Abe, Y Hisamitsu, M Mohamedi, Uchida, I

    CARBONATE FUEL CELL TECHNOLOGY 99 (20) 212-218 1999年

    出版者・発行元:ELECTROCHEMICAL SOCIETY INC

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    In order to clarify persisting controversies about the existence of superoxide and peroxide ions in molten carbonates, we have attempted to obtain vibrational spectra of these entities by Surface Enhanced Raman Scattering (SERS) technique. In situ experiments were carried out with solutions of potassium superoxide: (KO,) in molten (62+38)mol%(Li + K) carbonate eutectic at 650 degrees C. Raman line at 1047 cm(-1) appeared clearly after addition of KO2. Observed Raman line was assigned to the stretching vibration of superoxide.

  140. Electrochemical insertion behavior of lithium ions into mesophase pitch carbon films prepared by electrostatic spray deposition 査読有り

    SJ Lee, T Itoh, M Nishizawa, K Yamada, Uchida, I

    DENKI KAGAKU 66 (12) 1276-1280 1998年12月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:0366-9297

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    A carbon thin film (thickness, ca. 1 mu m) was prepared by the electrostatic spray deposition onto a Ni-substrate at 400 degrees C and heat-treated at 500 degrees C in vacuum. Electrochemical lithium ion insertion/extraction properties of the resulting carbon film electrodes were studied by cyclic voltammetry and electrochemical impedance spectroscopy in IM LiClO4/ (PC + EC). In the case of slow scan rates less than 10mV / 22sec in step potential electrochemical spectroscopy, two anodic peaks appeared, indicating that there are two different insertion / extraction mechanisms. Cole-Cole plots of impedance spectra showed two well-separated semicircles and a linear locus. The first semicircle at higher frequency range seems to correspond to the migration of lithium ions through passivating film at carbon surface, and the second semicircle and linear locus arise from carbon thin film itself.

  141. Irreversible conductivity change of Li1-xCoO2 on electrochemical lithium insertion/extraction, desirable for battery applications 査読有り

    M Nishizawa, S Yamamura, T Itoh, Uchida, I

    CHEMICAL COMMUNICATIONS (16) 1631-1632 1998年8月

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/a802962h  

    ISSN:1359-7345

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    Electrical conductivity of a sputter-deposited LiCoO2 thin film was studied in situ during electrochemical lithium extraction/insertion, revealing that the metallic behavior of Li1-xCoO2 induced by the initial lithium extraction did not revert to its original insulating state in the following successive reduction/oxidation cycles.

  142. Measurements of chemical diffusion coefficient of lithium ion in graphitized mesocarbon microbeads using a microelectrode 査読有り

    M Nishizawa, R Hashitani, T Itoh, T Matsue, Uchida, I

    ELECTROCHEMICAL AND SOLID STATE LETTERS 1 (1) 10-12 1998年7月

    出版者・発行元:ELECTROCHEMICAL SOC INC

    ISSN:1099-0062

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    The solid-state diffusion of lithium ion in carbon was directly investigated in single spherical particles of graphitized mesocarbon microbeads (MCMB, Osaka Gas Co.). In order to achieve electrochemical measurements focusing on a single particle, a molybdenum-filament microelectrode was maneuvered to make electrical contact with a single MCMB placed in an organic solvent mixture containing lithium ions as an electrolyte. This novel microelectrode technique gives electrochemical information about a MCMB particle, itself, without any dilution with additives such as organic binders. The chemical diffusion coefficient (D) of lithium ion was determined from potential-step chronoamperograms assuming spherical diffusion of lithium ions in the MCMB particle. The values of D were found to change the order between 10(-9) and 10(-11) cm(2)/s depending on the electrode potential. Plots of D showed pronounced minima at the potentials where the transformation of staging level of lithium intercalation compounds occurred. (C) 1998 The Electrochemical Society, Inc. S1099-0062(98)01-019-0.

  143. In situ SERS study of water molecules on silver electrodes in alkali-hydroxide solutions 査読有り

    T Itoh, Y Sasaki, T Maeda, C Horie

    SURFACE SCIENCE 389 (1-3) 212-222 1997年11月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0039-6028(97)00415-9  

    ISSN:0039-6028

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    In situ surface enhanced Raman has been used to study water molecules adsorbed on a silver electrode in 0.5 M alkali-hydroxide aqueous solutions. Raman spectra and cyclic voltammograms were measured simultaneously while the electrode potential was swept continuously. The alkali-hydroxide solutions were LiOH, NaOH, KOH and CsOH. Raman lines associated with water molecules are identified by a comparison with those obtained for aqueous solutions with D2O instead of H2O. Strong Raman lines, which are associated with the existence of oxygen species adsorbed on silver electrode, were observed in a limited region of electrode potential. The variation of Raman intensities of water molecules, when the electrode potential is scanned, is discussed in terms of the different roles of the cations of the respective alkali-hydroxide solutions. (C) 1997 Elsevier Science B.V.

  144. In situ Raman spectroscopic study of LixCoO2 electrodes in propylene carbonate solvent systems 査読有り

    T Itoh, H Sato, T Nishina, T Matue, Uchida, I

    JOURNAL OF POWER SOURCES 68 (2) 333-337 1997年10月

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/S0378-7753(97)02539-1  

    ISSN:0378-7753

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    Simultaneous measurements of in situ Raman spectroscopy and cyclic voltammetry have been carried out for thin film electrodes of LixCoO2 in propylene carbonate containing 1 M LiClO4. The Raman lines of 485 and 587 cm(-1) observed at LixCoO2 electrodes were attributed to the A(1g) and E-g modes of the LiCoO2, respectively. The Raman intensity of two lines changed drastically during the insertion/extraction of lithium ions. This effect can be explained by the reduction of the optical skin depth due to the conductivity change of LixCoO2. Phase transition from Raman-active phase to Raman-inactive phase is also conceivable. (C) 1997 Elsevier Science S.A.

  145. Raman microprobe spectroscopic study of interfacial species between Li anD Organic Solvents

    Takashi Itoh, Youko Matsutani, Isamu Uchida

    Denki Kagaku 64 (1) 76-79 1996年

    DOI: 10.5796/kogyobutsurikagaku.64.76  

    ISSN:1344-3542

  146. Raman microprobe spectroscopic study of interfacial species between Li and organic solvents 査読有り

    T Itoh, Y Matsutani, Uchida, I

    DENKI KAGAKU 64 (1) 76-79 1996年1月

    出版者・発行元:ELECTROCHEMICAL SOC JAPAN

    ISSN:0366-9297

  147. リチウム金属/有機溶媒界面のその場顕微ラマン分光測定 査読有り

    伊藤 隆, 松谷陽子, 内田勇

    電気化学および工業物理化学 64 76-79 1996年1月

︎全件表示 ︎最初の5件までを表示

MISC 13

  1. SiC薄膜を介したSi基板上エピタキシャルグラフェンの形成

    末光眞希, 末光眞希, 宮本優, 半田浩之, 齋藤英司, 今野篤史, 成田克, 吹留博一, 伊藤隆, 安井寛治, 中澤日出樹, 遠藤哲郎

    表面科学学術講演会講演要旨集 31st 2011年

  2. パルスモードホットメッシュCVD法によるGaN成長条件の最適化

    永田 一樹, 里本, 宗一, 片桐, 裕則, 神保, 和夫, 末光, 真希, 遠藤, 哲郎, 伊藤 隆, 中澤, 日出樹, 成田, 克, 安井 寛治

    信学技法Vol. 110, No-261 55-58 2010年10月

    出版者・発行元:電子情報通信学会

  3. Si基板上に成長させたグラフェンの共鳴ラマン分光

    宮本優, 半田浩之, 吹留博一, 伊藤隆, 末光眞希, 末光眞希

    応用物理学関係連合講演会講演予稿集 56th (1) 2009年

  4. 1. Graphene-on-silicon (GOS) technology for formation of high-mobility ultrathin channel layers on Si substrates.

    H. Handa, Y. Miyamoto, E. Saito, H. Fukidome, T. Itoh, M. Suemitsu

    IEICE Technical Reports 109 (16) 39-43 2009年

    出版者・発行元:一般社団法人電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    近年,産業への適応性から,SiCバルク基板の超高真空中アニールによるエピタキシャルグラフェンが大変注目を集めている.しかしポストCMOS材料としての適用を考慮すると,Si基板の導入と量産性に優れた成長技術が不可欠である.その要求に応えるため,我々は有機シランガスソースMBEによるSi基板上への3C-SiCエピ成長とその表面改質によるグラフェン形成,いわゆるグラフェン・オン・シリコン(GOS)技術を開発した.

  5. パルスモードホットメッシュCVD法による窒化物半導体のエピタキシャル成長

    安井寛治, 小前泰彰, 齋藤健, 末光眞希, 伊藤隆, 遠藤哲郎, 中澤日出樹, 成田克, 高田雅介, 赤羽正志

    電子情報通信学会技術研究報告 108 (269) 7-12 2008年10月

    出版者・発行元:電子情報通信学会

    ISSN:0913-5685

    詳細を見る 詳細を閉じる

    紫外・青紫LED,LD、また高温環境下で動作する電子デバイス用材料であるGaNの省資源成長法として期待されるホットメッシュCVD法において原料ガスの間欠供給及びメッシュのパルス加熱がGaN結晶膜の特性にどのような効果をもたらすか調べた。これまでルテニウム(Ru)を坦持したメッシュ状タングステン(W)を用いたホットメッシュCVD法により、メッシュ温度1100℃において良好な結晶性と深い順位からの発光が無く強いバンド端発光を示すGaN膜の成長に成功している。今回、気相反応を抑制することでGaN膜の特性を更に改善出来ないか、アンモニア及びアルキル金属原料ガスをパルス供給させ成長を行った。また、Wメッシュ上でアンモニアの吸着・分解・脱離をパルス的に行い基板に供給することでGaNの特性にどのような影響が生じるか調べた。結果、TMGをパルス供給させアンモニアを連続供給させた場合においてGaNの結晶性、発光特性ともに優れた膜が得られた。また、メッシュのパルス加熱によるGaN成長においては結晶性の改善を見出せなかった。

  6. Cat-CVD法による窒化物半導体の成長

    安井寛治, 田村和之, 深田祐介, 黒木雄一郎, 末光眞希, 伊藤隆, 成田克, 遠藤哲郎, 中澤日出樹, 高田雅介, 赤羽正志

    応用物理学関係連合講演会講演予稿集 54th (2) 2007年

  7. Hot-mesh CVD法を用いたSiC/Si(111)上へのGaN成長~AlNバッファー層の効果~

    深田祐介, 田村和之, 黒木雄一郎, 末光眞希, 伊藤隆, 成田克, 遠藤哲郎, 中澤日出樹, 高田雅介, 安井寛治, 赤羽正志

    応用物理学関係連合講演会講演予稿集 54th (2) 2007年

  8. Band-edge energies and photoelectrochemical properties of n-type AlxGa1-xN and InyGa1-yN alloys

    Katsushi Fujii, Masato Ono, Takashi Ito, Yasuhiro Iwaki, Akira Hirako, Kazuhiro Ohkawa

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 (2) B175-B179 2007年

    出版者・発行元:ELECTROCHEMICAL SOC INC

    DOI: 10.1149/1.2402104  

    ISSN:0013-4651

    詳細を見る 詳細を閉じる

    We studied photoelectrochemical properties of AlxGa1-xN for the first time, and compared with those of InyGa1-yN. The conduction band-edge energy of n-type AlxGa1-xN decreased with Al composition, however the valence band-edge energy did not significantly change. Saturated photocurrent obtained from dynamic photocurrent-voltage measurements under illumination also decreased with increasing Al composition. Greater Al composition also shifted the onset voltage to more negative direction. These phenomena can be explained by the changes of bandgap and band-edge energies with Al composition. (c) 2006 The Electrochemical Society.

  9. Si基板上SiC極薄膜の低温形成とユビキタスデバイスへの応用

    末光 眞希, 今野 篤史, 成田 克, 伊藤 隆, 安井 寛治, 中澤 日出樹, 遠藤 哲郎

    電気学会研究会資料. EFM, 電子材料研究会 2006 (15) 45-48 2006年10月3日

  10. 28aPS-94 層状ペロブスカイト型W酸化物へのLiインターカレーションによる新超伝導物質の探索(領域8 ポスターセッション)(領域8)

    梶田 徹也, 加藤 雅恒, 伊藤 隆, 小池 洋二

    日本物理学会講演概要集 59 (1) 577-577 2004年3月3日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  11. 22aPS-94 電気化学法による B クラスター物質への Li ドープの試み

    鈴木 尊士, 加藤 雅恒, 伊藤 隆, 小池 洋二

    日本物理学会講演概要集 58 (2) 533-533 2003年8月15日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  12. 22aPS-65 層状ペロブスカイト型 Nb、 Ta 酸化物への Li インターカレーションによる超伝導物質の探索

    梶田 徹也, 加藤 雅恒, 伊藤 隆, 小池 洋二

    日本物理学会講演概要集 58 (2) 526-526 2003年8月15日

    出版者・発行元:一般社団法人日本物理学会

    ISSN:1342-8349

  13. ESD法で調製したメソフェ-ズピッチカ-ボン薄膜のリチウムイオン脱挿入挙動

    李 栖宰, 伊藤 隆, 西沢 松彦, YAMADA Kohta, UCHIDA Isamu

    電気化学および工業物理化学 : denki kagaku 66 (12) 1276-1280 1998年12月5日

    出版者・発行元:電気化学会

    ISSN:1344-3542

︎全件表示 ︎最初の5件までを表示

書籍等出版物 16

  1. ラマン分光スペクトルデータ解析事例集

    伊藤 隆

    技術情報協会 2022年2月

  2. 電気化学・インピーダンス測定のデータ解析手法と事例集

    伊藤 隆

    技術情報協会 2018年12月

  3. Lecture Notes in Energy 32, Energy Storage in Batteries and Fuel Cells" in solar to Chemical Energy Conversion; Theory and Application, Part III pp.105-122.

    Tetsuya Kajita, Takashi Itoh

    2016年

  4. LiBの高容量・高耐久化のための電極-電解液(質)の界面制御技術と解析・評価法「ラマン分光法-リチウムイオン電池-」第9章第7節(2015) 297-301

    伊藤 隆

    情報技術協会 2015年2月

  5. 電気化学/インピーダンス測定のノウハウと正しいデータ解釈「ラマン分光法-リチウムイオン電池-」第3章、第1節[8] (2013) 128-132

    伊藤 隆

    情報技術協会 2013年

  6. IR分析「LiCoO2リチウム電池正極材料のラマン分光測定」第20章、第2節 (2013) 760-761

    伊藤 隆

    技術情報協会 2013年

  7. IR分析「リチウムイオン電池用負極材料のラマン分光測定」第20章、第3節 (2013)762-763

    伊藤 隆

    技術情報協会 2013年

  8. In-situ測定・分析テクニックおよび最新計測「各種測定法のIn-situ測定時のポイント、光散乱法/ラマン分光法によるIn-situ測定方法とポイント」第1章、第7節(2013)60-70

    伊藤 隆

    情報機構 2013年

  9. In-situ測定・分析テクニックおよび最新計測「リチウムイオン二次電池構成要素のIn situラマン測定」第3章、第1節(2013)257-264

    伊藤 隆

    情報機構 2013年

  10. スマートハウスの発電・蓄電・給電技術の最前線

    伊藤隆

    2011年3月1日

  11. 電池ハンドブック

    伊藤隆

    オーム社 2010年2月17日

  12. Lithium Batteries, Chronoamperometric studies of LiCoO2 and LiNiO2 particles during lithium-ion insertion/extraction

    Kaoru Dokko, Soichi Horikoshi, Matsuhiko Nishizawa, Takashi Itoh, Takayuki Abe, Isamu Uchida

    Electrochem. Soc., Proc. - Electrochem. Soc. 99-25 (2000), 290-297 2000年1月

  13. Intercalation Compounds for Battery Materials, EQCM investigations of LiMn2O4 thin films at elevated temperatures

    Takayuki Uchiyama, Matsuhiko Nishizawa, Takashi Itoh, Isamu Uchida

    Electrochem. Soc., Proc. - Electrochem. Soc. 99-24 (2000), 160-173 2000年1月

  14. Carbonate Fuel Cell Technology V, In situ Raman spectroscopic investigations of oxide chemistry in molten carbonates

    Takashi Itoh, Koji Abe, Yasunari Hisamitsu, Mohamed Mohamedi, Isamu Uchida

    Electrochem. Soc., Proc. - Electrochem. Soc., PV 99-20 (1999), 212-218 1999年1月

  15. Carbonate Fuel Cell Technology V, Convolution voltammetry applied for the diagnosis of adsorption phenomena during the oxygen reduction in alkali carbonate eutectic

    M. Mohamedi, Y. Hisamitsu, Y. Ono, T. Itoh, I. Uchida

    Electrochem. Soc., Proc. - Electrochem. Soc. 99-20 (1999), 242-252 1999年1月

  16. Carbonate Fuel Cell Technology V, Cathodic performance of in situ oxidized Ni+Al alloys in molten Li + Na carbonate eutectic

    Yasunari Hisamitsu, Yu Ono, Mohamed Mohamedi, Takashi Itoh, Takashi Kudo, Piotr Tomczyk, Isamu Uchida

    Electrochem. Soc., Proc. - Electrochem. Soc. 99-20 (1999), 337-346 1999年1月

︎全件表示 ︎最初の5件までを表示

講演・口頭発表等 45

  1. In Situ Raman Analysis for High Capacity Zinc Anode in Alkaline Solutions (Keynote Lecture) 招待有り

    Takashi Itoh

    7th International Conference on Functional Materials and Devices (ICFMD2022) 2022年8月25日

  2. 化学反応を観る -究極の電池に向けた光分析- 招待有り

    伊藤 隆

    「第136回」産学連携セミナー「寺子屋せんだい」、公益財団法人仙台市産業振興事業団 2019年10月24日

  3. In Situ Spectrospectroscopic Study for Zinc Electrodes in Highly Concentrated Alkaline Solutions, Keynote Lecture 招待有り

    伊藤 隆

    15th IUPAC International Conference on Novel Materials and their Synthesis (NMS-XV) 2019年9月9日

  4. In Situ Raman Analysis for High Capacity Zinc Anode in Alkaline Solutions, Invited Lecture 招待有り

    伊藤 隆

    Asia Pacific Society for Materials Research 2019 Annual Meeting 2019年7月27日

  5. 再エネ利用における蓄電技術の現状と課題の概要、取組紹介 招待有り

    伊藤 隆

    石油学会新エネルギー部会講演会 2019年2月21日

  6. In Situ Raman Spectroelectrochemistry for High Capacity Zinc Anode in Alkaline Solutions 国際会議 招待有り

    Takashi Itoh

    14th IUPAC International Conference on Novel Materials and their Synthesis (NMS-XIV) 2018年10月21日

    詳細を見る 詳細を閉じる

    Takashi Itoh and Azhagurajan Mukkannan

  7. 2次電池によるエネルギー貯蔵 ―リチウム電池から革新電池へー 招待有り

    伊藤 隆

    2018年 第65回応用物理学会春季学術講演会 2018年3月17日

    詳細を見る 詳細を閉じる

    伊藤 隆、 ムカンナン アザグラジャン

  8. In Situ SERS Analysis of Water Libration on Silver Electrode in Various Alkali Hydroxide Aqueous Solutions 招待有り

    IUPAC 13th International Conference on Novel Materials and their Synthesis (NMS-XIII) 2017年10月15日

  9. 電気化学エネルギー変換デバイスにおける極限電気化学界面の探索ーリチウム2次電池のサイエンスー 招待有り

    熊本大学 自然科学研究科 特別講演会 2015年12月10日

  10. In Situ Surface-enhanced Raman Analysis of Water Libration on Silver Electrode in Various Alkali Hydroxide Aqueous Solutions (Invited Lecture) 招待有り

    4th International Symposium on Energy Challenges and Mechanics (ECM4) - working on small scales 2015年8月11日

  11. 電気化学エネルギー変換デバイスにおける極限電気化学界面の探索ーリチウム2次電池のサイエンスー 招待有り

    第1回RIECENセミナー 2015年8月6日

  12. In Situ Raman Spectro-electrochemistry for Cathode Materials in High Voltage Lithium Secondary Batteries (Keynote Lecture) 招待有り

    IUPAC 10th International Conference on Novel Materials and Synthesis (NMS-X) 2014年10月10日

  13. 『電気化学エネルギー変換デバイスの現状と未来 ?2次電池と燃料電池ー』 招待有り

    RCASTセミナー(公開技術セミナー特別講演) 2014年3月14日

  14. In Situ FT-Raman Spectroelectrochemistry for Binder Included Cathode Electrodes in LiPF6 Electrolyte Systems (Keynote Lecture) 招待有り

    IUPAC 9th International Conference on Novel Materials and Synthesis (NMS-IX) 2013年10月17日

  15. In Situ FT-Raman Spectroelectrochemistry for Lithium Ion Battery Cathode 招待有り

    IUPAC 8th International Conference on Novel Materials and Synthesis & 22nd International Symposium on Fine Chemistry and Functional Polymers 2012年10月14日

  16. 2次電池・燃料電池の評価方法と今後の研究開発動向 招待有り

    ホンダ東陽テクニカKEISOKU Tec. 2012 2012年8月22日

  17. その場ラマン分光法を用いた高エネルギー電極反応の探索 招待有り

    サーモフィッシャーサイエンティフィック株式会社ユーザーズフォーラム2012 2012年6月8日

  18. リチウムイオン二次電池の研究最前線 招待有り

    東陽ソリューションフェア2011 2011年11月2日

  19. 2次電池の信頼性評価技術 招待有り

    東京大学ITSセミナーin仙台 2011年10月24日

  20. In Situ FT Raman Spectroelectrochemistry on Highly Polarized Cathode Materials for Lithium Ion Batteries 招待有り

    IUPAC 7th International Conference on Novel Materials and Synthesis (NMS-VII) & 21st International Symposium on Fine Chemistry and Functional Polymers (FCFP-XXI) 2011年10月16日

  21. 固体高分子形燃料電池の高性能化と低コスト化−ハイブリッドセパレータとFePt触媒からのアプローチ− 招待有り

    石油学会東北支部講演会 2010年11月18日

  22. 電気化学エネルギー変換デバイスの最先端−燃料電池と2次電池 招待有り

    みやぎ高度電子機械産業振興協議会 エネルギーデバイス市場・技術研究会 2010年10月22日

  23. In Situ Spectro-Electrochemistry for Energy Conversion Interface 招待有り

    Sony Electronics Singapore Company Invited Lecture 2010年9月21日

  24. In Situ Raman Spectroelectrochemistry on Highly Polarized Cathode Materials for Lithium Ion Batteries 招待有り

    5th Asian Conference on Electrochemical Power Sources 2010年9月17日

  25. リチウム二次電池の電極反応 招待有り

    2010年秋季応用物理学会学術講演会 2010年9月15日

  26. 電極材料の過剰な負荷条件下におけるその場振動分光 招待有り

    日本金属学会分科会シンポジウム 2010年7月29日

  27. 二次電池の信頼性評価技術ー電気化学エネルギー変換デバイスのサイエンスー 招待有り

    第1回次世代移動体システム研究報告会 2010年3月12日

  28. 電極材料の過剰な負荷条件下におけるその場振動分光解析 招待有り

    第24回JFCAテクノフェスタ 2010年1月25日

  29. 「電気化学エネルギー変換デバイスの最先端 −燃料電池と2次電池− 招待有り

    NPO法人環境エネルギー技術研究所第2回SFTEEセミナーDC利用技術の最先端 2009年11月27日

  30. In Situ Raman Spectroelectrochemistry for Energy Conversion Interfaces 招待有り

    5th IUPAC International Symposium on Novel Materials and Synthesis (NMS-V) & 19th International Symposium on Fine Chemistry and Functional Polymers (FCFP-XIX) & 3rd Symposium on Power Sources for Energy Storage and their Key Materials (PS-III: Internation 2009年10月18日

  31. 燃料電池用Fe-Pt電極触媒ナノ粒子の特性評価 招待有り

    社団法人未踏科学技術協会ナノ粒子研究会第45回公開講演会 2008年12月17日

  32. In Situ Raman Photo-electrochemistry for GaN electrodes in aqueous solutions 招待有り

    University of California Santa Barbara Special Semiar 2008年5月23日

  33. 電気化学エネルギー変換デバイス材料のその場ラマン分光 招待有り

    日本金属学会2008年春期講演大会 2008年3月26日

  34. In Situ Raman Spectroelectrochemistry for Energy Conversion Interfaces 招待有り

    Chemistry Department Special Seminar, University of California Riverside 2008年2月19日

  35. In Situ SERS Spectroelectrochemistry of Oxide Chemistry at Energy Conversion Interfaces 招待有り

    35th International Conference on Spectroscopy, Colloquium Spectroscopicum Internationale XXXV 2007年9月23日

  36. 水素発生のための光電気化学反応のその場観察 招待有り

    第68回応用物理学会学術講演会シンポジウム”光と半導体による新しいエネルギー生成と環境浄化” 2007年9月4日

    詳細を見る 詳細を閉じる

    伊藤 隆,藤井克司,八百隆文

  37. その場赤外・ラマン分光法による電極表面解析 招待有り

    表面科学会 第26回表面科学講演大会 2006年11月6日

  38. In situ Raman spectroelectrochemicstry for energy conversion interfaces 招待有り

    56the Annual Meeting of the International Society of Electrochemistry 2005年9月25日

  39. 高エネルギー界面のスペクトロエレクトロケミストリー 招待有り

    平成17年度 化学系学協会東北大会 2005年9月23日

  40. In Situ Surface-Enhanced Raman Scattering Spectroelectrochemistry of Oxygen Species 招待有り

    Faraday Discussions 2005年9月19日

  41. ナノ構造エネルギー変換デバイスとラマン分光 招待有り

    第35回マテリアルズ・テーラリング研究会プログラム 2003年7月31日

  42. エネルギー変換デバイスのその場ラマン分光と電気化学測定に関する研究 招待有り

    社団法人 電気化学会 創立70周年記念大会 2003年4月1日

  43. In Situ Raman Spectroelectrochemistry for Battery Active Materials 招待有り

    1st Sino-Japan Seminar on Advanced Battery Materials 2002年10月7日

    詳細を見る 詳細を閉じる

    Takashi Itoh, Mohamed Mohamedi and Isamu Uchida

  44. In Situ Raman Spectroscopy for Lithium ion batteries 招待有り

    4th Chicago Battery Workshop 2000年4月10日

  45. In Situ Raman Spectroscopy for Lithium ion batteries 招待有り

    Battery Conference in Polish Academy of Sciences 1999年10月24日

︎全件表示 ︎最初の5件までを表示

共同研究・競争的資金等の研究課題 23

  1. 酸化物フリーCuナノワイヤが実現する完全塗布型太陽電池

    横山 俊, 伊藤 隆

    2022年4月1日 ~ 2026年3月31日

  2. 金属の溶解析出反応を制御する有機物添加剤の超高感度ラマン分光学解析

    伊藤 隆, 横山 俊

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2022年4月1日 ~ 2025年3月31日

  3. Cuナノワイヤを基軸にした高性能・高耐久な透明導電膜の創製と太陽電池応用

    横山 俊, 伊藤 隆

    2019年4月1日 ~ 2023年3月31日

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    銅ナノワイヤを太陽電池の透明導電膜へ応用するため、現在用いられている酸化インジウムスズの性能や耐久性を超えるために研究を進行してきた。現在までに、形状、表面制御によってITOと同等以上の性能発現に成功し、更にAg被覆によって数百時間の耐久性付与に成功している。しかし、実際の太陽電池の透明導電膜として使用するためには、数年から数十年の耐久性を必要とするため、酸化亜鉛によるナノワイヤ被覆による耐久性の向上を検討した。 酸化亜鉛被覆は研究代表者の開発しているアミンヒドロキソ亜鉛錯体の脱水による酸化亜鉛薄膜形成法を展開し、被覆法の開発を行った。アミンヒドロキシ亜鉛は、アンモニア水溶液に酸化亜鉛を溶解し得ることが出来るが、これまでのアンモニア濃度では、ナノワイヤとの反応時にpHが高く、ナノワイヤが劣化するため、アンモニア濃度、亜鉛濃度を制御した結果、アンモニア濃度をアミンヒドロキソ亜鉛錯体を形成可能な範囲で低減し、14.8Mから1M程度まで低減出来た。また、アンモニア濃度の低い場合に形成される酸化亜鉛はこれまで水酸化亜鉛を多く含んでいたが、水酸化亜鉛の比率が低く、質のよい酸化亜鉛を形成可能であることを明らかとして、詳しい機構は解明中である。この溶液条件を用いたところ、ナノワイヤを劣化させずに酸化亜鉛を数nm程度で被覆することに成功した。現在劣化環境下で耐久性を調査中であるが、Ag被覆よりさらに耐久性を付与可能であることが示唆されている。

  4. ソフト化学法による高アモルファス型高密度Na吸蔵放出材料の開拓

    梶田 徹也, 伊藤 隆

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Young Scientists (B)

    研究機関:Tohoku University

    2016年4月1日 ~ 2018年3月31日

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    本研究課題の目的は、ソフト化学法を用いて高度にアモルファス化した材料を創製し、新たなNa二次電池用電極材料群を開拓することにある。ソフト化学法により Si, Geにてアモルファス構造をとりえる材料を創製できることを確認した。しかし、アモルファスGe系材料のみ、Na二次電池特性を示した。ソフト化学合成を行う際、Zitle相NaMを酸化するためのアルコール種に2級アルコールである2-プロパノールを用いる事で、数ミクロンの微粒子を持つ材料の合成が可能になった。また、エーテル系溶媒をNa二次電池電解液に用いることで、アモルファスGe材料の電気化学的特性が大幅に向上した。

  5. 高活性電極界面における溶媒和イオン反応過程のその場分光

    伊藤 隆, 吉本 惣一郎, 梶田 徹也

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2015年4月1日 ~ 2018年3月31日

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    研究代表者の研究グループでは、電池の電極反応を分光学的な視点より解明している。電池特性の鍵である高活性な電池電極界面では、溶媒和した分子が溶媒和・脱溶媒和しながら電極反応が進行していると考えられるが、その反応についての詳細は未だ推測の域を脱していない。当該研究課題では、分光学的手法であるラマン分光法などの振動分光学的な手法を高活性な電池材料界面に展開する。得られる知見は、急速充放電を必要としている電気自動車用車載リチウムイオン2次電池の研究開発に大きな知見を与えると考えている。

  6. 電気化学反応の高速可視化装置とリチウム電池層間反応への応用

    板谷 謹悟, 伊藤 隆, 吉本 惣一郎

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2013年4月1日 ~ 2016年3月31日

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    本研究課題では、世界に先駆け、電気化学および界面化学に衝撃を与える成果を出した。研究代表者自身が発明・開発した電気化学STM/AFMの装置の登場によって電極表面の原子構造、吸着構造の可視化することになったが、電極表面の面内観察領域は最大数ミクロンと狭く電極反応のダイナミクスをリアルタイムでの追跡は非常に困難であった。研究代表者は、本研究課題により、電気化学的な環境下において原子段差を直接観測できる特殊微分干渉顕微鏡の開発・改良を行い、重要な反応の可視化に初めて成功した。

  7. 電気化学界面における炭素-炭素間電子移動過程のその場振動分光解析

    伊藤 隆, 梶田 徹也

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2013年4月1日 ~ 2015年3月31日

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    電気二重層領域に存在する水分子の動的挙動の解明は電気化学の根源的問題であり、電極反応に関わる水分子の役割は興味深い研究対象である。表面増強ラマン分光法は、通常のラマン散乱より著しく散乱強度が増大する現象として知られている。SERSを電極反応の解析に応用すると、電極表面に吸着する分子数が少ない場合にも吸着現象に関する情報をラマン散乱を通じて得ることが可能である銀電極-アルカリ水溶液界面のその場SERS測定を電極電位を印加しながら行い、銀電極近傍の水分子の動的挙動、特に水分子ライブレーション振動の電極依存性、カチオン依存性について検討を行った。

  8. 単層カーボンナノチューブ薄膜を使用した高性能リチウムイオンキャパシタ正極の開発

    佐藤 義倫, 伊藤 隆, 利根川 敏, 羽藤 之規, 宮川 里咲

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Young Scientists (A)

    研究機関:Tohoku University

    2011年4月1日 ~ 2014年3月31日

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    カルボキシル基を持つ高結晶性単層カーボンナノチューブ薄膜を正極に用いたリチウムイオンキャパシタの特性を調べた。キャパシタの容量は高レートでの低下が少なく、過充電では静電容量の低下、内部抵抗の上昇を抑えられた。単層カーボンナノチューブの静電容量が大きくなれば、高性能なリチウムイオンキャパシタを作製できる。一方で、過放電ではリチウムイオンキャパシタの特性が低下する。今後は過放電時の単層カーボンナノチューブ電極で起きている現象を明らかにする。 アミノ化単層カーボンナノチューブ電極の水系電解質電気二重層キャパシタ特性がカルボキシル化単層カーボンナノチューブ電極のものより優れていることを明らかにした。

  9. エネルギー・環境応用を目指した高結晶性ナノ粒子の創製プロセス開発

    ビー ジャヤデワン, 伊藤 隆, 松本 高利, 篠田 弘造, 粕谷 亮

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:The University of Shiga Prefecture

    2010年 ~ 2012年

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    金属粒子の合成技術開発に関する基礎的研究をベースとした実施計画を立て、エネルギー・環境分野への応用を目指した高結晶性ナノ粒子の創製と物性評価を行った。光電変換材料開発に関連して、サイズ及び形状を制御した純粋な酸化銅(CuO、Cu2O)ナノ粒子の合成技術を開発し、その半導体特性を確認すると同時に酸化銅-C60太陽電池セルを作製し、量子効率を評価した。また燃料電池触媒として、貴金属であるPt使用量の減量、PtのCO被毒改良と使用後のPt回収を目的としたFe-Pt磁性合金ナノ粒子合成と特性評価を行い、Fe33Pt66ナノ粒子は純Pt粒子に比べて高性能を示すことを確認した。また、 Ni95Pt5及びNi90Pt10磁性合金ナノ粒子を合成し、水素化反応においては純Pt粒子と同程度の触媒性能を示すことを確認した。さらに、電磁波吸収体・アンテナ素材としての応用を目指したFeCoやFeNiなどFeベース合金粒子の合成技術開発と物性評価を行い、それらの材料のポテンシャルや課題を明確にした。特にFeCo合金粒子のアンテナ材料としての高いポテンシャルを確認した。

  10. 電気化学その場ラマン分光によるオキサイドケミストリーの新展開

    伊藤 隆

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Young Scientists (A)

    研究機関:Tohoku University

    2006年 ~ 2008年

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    電気化学的な条件下で酸素還元反応を進行させ,その場ラマン分光法にて電極界面からのラマンスペクトルを測定すると,酸素分子に起因したラマン線が観測され,サイドオン型やエンドオン型といった吸着形式の中間体を取ることが本研究にて判明した.また,この酸素分子の吸着は,電極電位に依存している.この反応解析は,科学の根源をなす反応として古くから注目されており,当該研究課題にて酸素還元反応の反応経路解析に一石を投じている.

  11. 1ナノメータ粒子の精密物性解析と電子的材料機能の開拓

    粕谷 厚生, 伊藤 隆, 前川 英己

    2006年 ~ 2008年

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    本研究の目的は機能性半導体として有用なII-VI族化合物の一つであるCdSeについて、(CdSe)13、(CdSe)19、(CdSe)33、(CdSe)34、(CdSe)48、等の直径1ナノメートル台の粒子を溶液法で選択的に大量合成し、原子数に依存する物性を詳細に解析することによってバルクでは実現せぬ電子機能を開拓して応用に役立てる萌芽的研究を実施することであった。この分子的ナノ粒子は原子と固体の中間に位置する新しい物質群と見なすことが出来、物質科学と材料工学に未開分野に属する。初年度より以下の実験を実施し、成果をあげた。 1. ナノ粒子の生成過程の解析と単離条件の決定(粕谷、伊藤) 1ナノメータ粒子として(CdSe)13、(CdSe)33、(CdSe)34、(CdSe)48、を単離する条件を見出した。 2. 核磁気共鳴(NMR)によるナノ粒子の構造解析(前川、伊藤) 得られた(CdSe)13、(CdSe)33、(CdSe)34、(CdSe)48、についてNMR測定を行い、(CdSe)13ではCdとSeからの鋭いピークをそれぞれ1本、(CdSe)48では2本観測し、試料が完全に単離されて単一であること、原子配列の対称性が極めて高いことが証明された。 3. 顕微分光によるナノ粒子の物性解析(伊藤、粕谷) 局所的な分光を行うための顕微装置を立ち上げ、それぞれの1ナノメータ粒子の光吸収、発光、ラマン散乱測定を行い、基礎的な電子物性と結合状態を明らかにした。 3. ナノ粒子の電子的、電気化学的特性の評価(伊藤、前川) 次ぎに電気化学測定を行い、1ナノメータ粒子の化学的特性、光電気化学反応、触媒効果、を調べた 4. ナノ粒子の整列薄膜化と集積的電子材料機能の開拓(伊藤、前川、粕谷)更にこれら単離された1ナノメータ粒子を基板上に整列させた薄膜を作製し、互いの相互作用或いは干渉効果による、諸特性の増強、先鋭化、の有無を解析した。 以上の結果を基にして1ナノメータ粒子及び集合体のフォトニックデバイス、光単電子素子、蓄電材料、分子認識センサー、電力変換触媒、等としての特有の性能を評価し、原子数の精度でナノ構造と材料機能を捉える物質科学と材料工学への貢献を総括した。

  12. 高機能性微小粒子の集積回路網による化学変換デバイスの構築

    粕谷 厚生, 伊藤 隆, 田路 和幸, 須藤 彰三, 樋口 秀男, 川添 良幸

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2004年 ~ 2006年

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    原子が十数個から数千個結合して出来た微小粒子は、構成原子数に著しく依存する特異な電子状態と化学活性表面を持ち合わせた高機能性物質である。本研究では粒子の原子数を揃えて2次元或いは3次元に配列させた集積回路網を組み上げ、入射する電子、原子、分子、イオンが粒子表面或いは内部での反応を介して検知、伝達、分解、組み替え、蓄積される高速且つ高効率な化学変換デバイスの構築を試みた。 研究課題は、1.高機能性微小粒子の合成、2.集積回路網の組み上げ、3.化学変換デバイスの作製に分かれる。バルク結晶では実現しないような特性を有する物質を設計制作する観点から最大限に微小な粒子を作製することに主力を置き、光学的に有用なII-VI族半導体の一つであるCdSeについて、粒径が1nm台で原子数まで正確に揃ったナノ粒子、(CdSe)_n、を作製する方法を見出した。このように微小な粒子では原子数も100を割り、分子的となる。このため集積化、デバイス化に対しても原子レベルでの構築が可能であり必要ともなり、微視的な原子配列に基づく特徴的な物性を解析して高材料機能を生み出すナノ科学と技術としての貴重な手法を導出すことが出来た。 高機能性微小粒子の合成については、特に(CdSe)_nについて反応条件を整えることによって(CdSe)_<13>、(CdSe)_<34>、(CdSe)_<48>、(CdSe)_<60>等を単離することが出来た。これは(CdSe)_nについて原子数nが100を割るように少なくなると、粒子の安定性がnに著しく依存するようになり、13、34,48,60,などの特定の数でのみ安定となって成長するためとわかった。これにより、原子数まで正確に揃った1nm粒子を得る方法が見付かった。 集積回路網の組み上げについては単に配列させるに留まらず、有機ポリマー上に規則配列させた試料を作製することが出来た。 化学変換デバイスについても例えば粒子表面をトリオクチルフォスピン(TOP)と結合させると(CdSe)_nの発光効率を2桁以上向上させることが出来、ローダミンなどの実用有機色素と同等の特性を得る素子を作製することが出来た。 何れも原子レベルでの精密な構造制御によって性能や特性を飛躍的に高めた1nm粒子の作製と物性解析に基づき得られた成果である。

  13. ポーラスシリコンを用いた太陽光動作光触媒素子の開拓

    粕谷 厚生, 須藤 彰三, 伊藤 隆, 香川 昌宏

    2003年 ~ 2005年

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    本研究では水素原子を終端したシリコン完全結晶表面をポーラスシリコンの理想モデルと見なして単純な平坦面から凸凹なポーラス面に至る試料について順次光電気化学的特性を解析し、光触媒効果を原子的素過程として解明する。即ち光照射によりシリコン内部で励起された電子が表面に吸着する水素と電荷の授受を行い、分子として脱離する過程を電気化学分光、電子分光、赤外分光などの測定技術を駆使して詳細に解析することを目的とした。 初年度に光電気化学セルを作製し、2年度に引き続いて電解液中の電気化学測定と走査トンネル顕微鏡、原子間力顕微鏡測定並びにラマン散乱分光による反応過程のその場観察を行った。また赤外分光、超高真空走査トンネル顕微鏡と高分解能電子エネルギー損失分光の組み合わせ装置により、反応中間体や生成物の同定を試みてきた。 3年次において以下の結果と結論を得た。 1.シリコンは表面を水素で終端することにより、還元電位より卑であれば電機化学的に極めて安定であることがわかった。これにより良質なショットキ障壁が形成される。 2.H+がHに還元される反応では表面を終端する水素は脱離することなく結合し、安定な電極として働くことが重水素をつかった赤外分光測定で明らかになった。 3.更にこの反応において電解液中のHは表面のみならず内部にまで侵入し、表面準位を形成することがわかった。この表面準位が電気化学反応の効率に重要となることがわかった。これに表面の凸凹が加わると表面積を増やすことのみならずに反応活性点も増加し、極めて高効率の電極になることが始めて理解されるに至った。

  14. 電気化学In Situラマン分光法のアゾ化合物を修飾した炭素電極への展開

    伊藤 隆

    2002年 ~ 2004年

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    当該研究課題は,(1)その場ラマン分光システムをアゾ化合物で修飾したカーボン電極に展開する,(2)アゾ化合物で修飾したカーボン電極を固体高分子型燃料電池の電極材料として用い,その電極特性を検討することを目的としている.研究の初期段階において4-NitoroAzoBenzene等をカーボン電極に修飾することに成功した.研究の第一段階としてその吸着過程をIn Situラマン分光測定を行い,吸着過程の電極電位依存性を解明した.本年度はその手法を幅広い電極,分子種に展開した. 吸着分子種の幅を広げつつ,電極反応過程の詳細なる検討を行った.アセトニトリル中においていて4-NAB,AB(AzoBenzene)等のアゾ化合物のカーボン電極の吸着過程を中心にその場ラマン分光測定を行った.昨年度までの研究成果において,4-NABの吸着過程の分光学的研究を行っており,これまで(a)NABは非常に大きなラマン散乱強度を持つラマンバンドが存在する,(b)カーボン電極へのNABの吸着は比較的強固である,(c)NABは良い電子伝導性をもつなどの実験結果を得ることができている.これを踏まえた吸着過程の電極電位依存性を検討した結果,電極界面における分子の配向,単分子層吸着のメカニズム等を解明することができた.同様な解析手法を展開しつつ,その場ラマン測定の高感度化を試みた結果,高感度化により,幅広い分子種のラマン測定のみならず,多種多様な電気化学反応解析を行うことができた.この実験結果より,電気化学反応の詳細を描くことができたと考えている.

  15. 固体高分子形燃料電池用in-situ/ex-situ電気化学計測システムの開発

    梅田 実, 内田 勇, 岸岡 真也, 山田 明文, 伊藤 隆

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Nagaoka University of Technology

    2002年 ~ 2003年

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    固体高分子形燃料電池単セルに電気化学計測技術を適用してセル中で(in-situ)電気化学計測を行い,また使用される材料単体の計測をセル外で(ex-situ)行う,新規な電気化学計測システムを構築した。従来,固体高分子形燃料電池(PEFC)の電気化学的試験評価は,単セルそのものを用いた電流-電圧特性の測定に終始していたが,本研究では実際に使用される環境下で計測する電気化学的基礎手法を確立した。主な研究成果は,以下の通りである。まず,多孔質マイクロディスク電極と多孔質マイクロリング電極を用いて,電極触媒単体および電極触媒/固体高分子電解質積層構造の電気化学特性を計測できるようにした。次に,電解質膜の膜厚方向の精密なプロトン伝導率をマイクロ電極の使用により可能とした。これを単セルにおけるカレントインタラプタ法による伝導率と比較したところ,よい一致を示した。一方,マイクロ電極を用いて固体高分子電解質膜単独のアルコールクロスオーバ測定方法を開発した。このことにより,簡便な電気化学測定によりクロスオーバの定量化が可能となった。また,電気化学計測用分光光度計を用い,芳香族アルコールの酸化還元機構の研究を通して,その新規燃料としての可能性を研究した。さらに,マイクロ電極を用いてナフィオン膜のイオン伝導性に及ぼす水および水とアルコール混合比の影響を研究した。これは,PEFCならびに直接メタノール形燃料電池(DMFC)運転に際して電解質膜の基礎特性となるものである。以上のように,固体高分子形燃料電池単セルと使用される材料の各電気化学特性を計測しあるいは比較することで,従来は困難であった材料ないしはセルシステムの電気化学研究が大きく進展した。

  16. メソフェーズ炭素薄膜電極のラマン散乱分光法による動的評価 競争的資金

    2002年4月 ~

  17. ウルトラマイクロ電極を用いる高分子電解質/電極触媒界面の評価システムの構築

    内田 勇, 伊藤 隆, MOHAMEDI Mohamed, 梅田 実

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2001年 ~ 2002年

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    新規ウルトラマイクロ電極群を作製することにより,従来は困難であった高分子電解質/電極触媒界面の電気化学計測を簡便に行える電気化学計測システムを構築した。抵抗率の大きな固体高分子電解質においてマイクロ電極はiを小さくできるためiR降下の少ない電気化学計測を可能とした。また集合型のマイクロ電極を用いることで,電極触媒の関与する反応機構を明らかにした。結果的に本研究により,固体高分子形燃料電池(PEFC)の計測に資する技術が構築された。主な研究成果は,以下の通りである。まず,集積化マイクロ電極を創製し,ガスフェーズの電極反応を計測できるようにした。また,マイクロアレー電極を使用して,ナフィオン膜のイオン伝導性に及ぼす水および水とアルコール混合比の影響が明確にされた。これは,PEFCならびに直接メタノール形燃料電池(DMFC)の運転に際して基礎特性となるものである。またマイクロアレー電極を用いて,メタノール電極酸化反応の反応中間体を電気化学的に検出することに初めて成功した。このような計測には,通常回転リング-ディスク電極が使用されるが,中間体の検出の報告はなく,今回の検出によりDMFCの燃料極反応機構の理解が進展した。次に,多孔質マイクロディスク電極(電極先端をエッチングにより空洞を設けそこに粉体を充填する)を作製し,これまで単独で計測することが難しかったサブミクロン径の電極触媒の,簡便な電気化学計測が可能となった。さらに,多孔性マイクロリング電極を作製し,先端に高分子電解質/電極触媒の積層構造を形成できるようにし,膜電極構造体(MEA)の電気化学計測を可能にした。以上のように,複数の新規ウルトラマイクロ電極の設計と作製により,従来から困難とされてきた高分子電解質/電極触媒界面の電気化学研究が大きく進展した。

  18. 電気化学InSituラマン分光法の高温溶融炭酸塩系への展開

    伊藤 隆

    2000年 ~ 2001年

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    (1)溶融炭酸塩へのIn Situラマン分光法の展開を行うため,In Situ測定の可能な高温電気化学セルの作製を行った.さらに,溶融炭酸塩の成分組成の条件出し,ガス雰囲気の決定等を行うための実験を行った.共晶組成であるLi/K=62/38を923Kに加熱し,溶融炭酸塩からのIn Situラマン測定を行った. (2)溶融炭酸塩中における酸素活性種(スーパーオキサイド,パーオキサイド)の同定をおこなうために,外部からKO_2,Li_2O_2等の活性酸素種を含む化合物を溶融炭酸塩に投入した場合のラマンスペクトルの測定にはじめて成功した. (3)共晶組成であるLi/K=62/38を923Kに加熱した溶融炭酸塩のガス組成依存性を検討した.これまでのところ,In Situラマンスペクトルのガス組成依存性はみられなかった. (4)さらに上記のIn Situ測定に加えて,電位規制下における金電極-溶融炭酸塩界面における電気化学反応を,高温In Situラマン分光法にて観察している.これまでのところ,酸素活性種に帰属できるラマン線が観測されている.

  19. 溶融炭酸塩中における金属表面の分光学的研究 競争的資金

    2000年4月 ~

  20. プロチウム材料溶液界面のマイクロACインピーダンス解析と電極過程のモデル化

    伊藤 隆, 梅田 実, 内田 勇

    2000年 ~ 2000年

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    当該研究は,ニッケル水素2次電池への応用を念頭においたプロチウム固溶材料の材料特性評価を行ったものである.マイクロ電極法とACインピーダンス法を組み合わせた電気化学測定は,プロチウム固溶材料(Mm系合金材料,Mg_2Ni,Pd)-電解液界面系における二重層容量,電極抵抗,電荷移動抵抗等の見積もりが可能であった.さらに,プロチウム固溶過程のモデルを厳密等価回路を用いて表現し,得られた結果との整合性を議論することができた.特に,Mg_2Ni系粒子のプロチウムインサーション反応についての知見は,特に良い電気化学的整合性をみることができている. このマイクロ電極を用いた電気化学的手法は,従来の電池として用いられる電池活物質そのものの特性を評価することができる.結着剤,導電助剤等加えたコンポジット電極を用いた評価では,これらの影響が含まれるため,不確定性が大きい.また,プロチウムの拡散係数も,信憑性のおけるデータが得られており,この測定手法を応用することも可能であると考えている.また,マイクロ電極の手法は,電池の小型化という側面も持ち合わせている.マイクロレベルで電極を設計・制作し,電極の任意の位置に堆積して薄膜化する技術をもってすれば,現在の携帯機器に代表されるような新型2次電池技術に新たな側面を付与することができ,新たな技術の展開が期待される.さらにこのマイクロ電極を用いた電気化学測定を,燃料電池系にさらに展開し,燃料電池における電極触媒効能の評価を行っている.

  21. ラマン分光による光インサーション材料の界面構造解析

    伊藤 隆, 内田 勇

    1999年 ~ 1999年

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    当該研究は,光インサーション材料による構造規制界面の構築とそれによる新規な界面構造の機能発現過程を電気化学測定と組み合わせたラマン分光法やマイクロ電極法により追跡し,リチウムイオン2次電池材料における光充電の可能性追及とその機能発現のメカニズムを分光学的手法により解析することが目的である.当該領域で用いたラマン分光法は,非常に浅い測定深さを有しており,電気化学における根源的問題である固-液界面解析に有用な研究手法である.光インサーション反応は,光エネルギーを化学エネルギーに変換する独創的発想であり,この研究成果より,遷移金属化合物に新たな機能を有する界面構造が創製されると考えている.主眼となる研究手法は,その場ラマン分光法とマイクロ電極法である.特に静電噴霧法で作製したLi_xMn_2O_4薄膜電極を研究対象とし,光照射(インサーション)と対応した界面の極微細構造変化や格子震動変化を追跡し,光充電過程をミクロスコピックな観点から記述することを試みた.さらに複数の励起波長に対応したスペクトル測定を行い,電極材料のバンドギャップを意図したスペクトル解析を行った. はじめに有機電解液中におけるLi_xMn_2O_4薄膜電極のサイクリックボルタモグラム(CV)の測定を行った.Li_xMn_2O_4へのリチウムイオンの脱挿入反応に起因した電流応答が見られている.このCV測定を行いながらスペクトル測定を行なった.その結果,Li_xMn_2O_4中のxの減少に伴い,スペクトルに変化が見られ,新たなラマン線が出現した.この実験結果は,有機溶液中におけるLi_xMn_2O_4その場ラマン測定に初めて成功したことを意味している.さらに,スペクトル変化はLi_xMn_2O_4の相構造の変化により説明することができている.また,ラマンスペクトルの励起波長依存性についても検討を行なった.これは,Li_xMn_2O_4のバンドギャップを意図したスペクトル測定である。励起波長を514.5nm(2.48eV)から647.1nm(1.97eV)とすると,格子振動に起因するラマン線の散乱強度が減少した.これは,Li_xMn_2O_4の相変化に伴い,バンドギャップが変化したため,スペクトルの励起波長依存性が見られたと考えている.また,ラマン散乱強度は振動数に比例して減少することが知られており,これが,当該成果で得られた実験結果と合致することも否めない.どちらが優位であるかを現時点で判断できないが,当該課題で得られた励起波長を変化しながら測定したその場ラマンスペクトルより得られた知見は,壮大な光電気化学反応に大きな影響を与えると確信している.本研究は"光充電可能な2次電池"として大きな可能性を秘めており,今後さらなる研究が必要であろう.現在の携帯機器に代表されるような新型2次電池に新たな側面を構築することにより,新たな新技術が生まれだすと考えている.

  22. リチウムイオン脱挿入化合物のミクロ構造制御と単一粒子レベルの電池特性評価

    内田 勇, 松木 健三, 伊藤 隆, 西澤 松彦, 漆畑 広明, 仁科 辰夫

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:TOHOKU UNIVERSITY

    1998年 ~ 1999年

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    本研究は二つの大学がそれぞれ異なる手法を用いて協力し,電気自動車等への応用が期待される高性能2次電池,いわゆるリチウムイオン電池の材料開発と評価法の確立に取り組んだものである. 1.山形大では,各構成原子を原子レベルで均一に混合でき,且つ多成分の層状化学物を簡便かつ系統的に合成できるクエン酸錯体法を改良・駆使してミクロ構造制御合成を行った。特に,今後の材料展開を予想してニッケル系およびマンガンスピネル系材料で焼成条件の最適化を進め,サイクル安定性に優れた材料を得ている.(1)LiNiO_2系ではLiやNiに対するクエン酸のモル比を量論比で1.5以上とし,分散仮焼することにより反応を抑制し,最終的に酸素中720℃,15時問以上の焼成で安定な材料を得た。(2)LiCoO_2やLiMn_2O_4の場合は,クエン酸錯体生成後,空気中300℃以下の低温仮焼段階で既にサブミクロンサイズの微粒子の基本骨格が生成し,空気中700℃,4時間の本焼成により,結晶構造が十分に発達した粒径10μmの酸化物が合成できた。 2.東北大では,微量の電池材料で迅速に電気化学特性を評価し,電池材料としての1次スクリーニングを速度論的評価を交えて行うマイクロ電極法を確立し,それらの結果を実電池用試料に反映させるべく山形大及び三菱電機側に流すと共に,ここからフィードバックされる試料を測定に供した。成果を羅列すると,単一の電池活物質粒子(〜10μm)について,(1)分極化での粒子の機械的安定性のin-situ観察,(2)高電圧(〜5V)ボルタンメトリーによる電気化学的安定性評価(3)ACインピーダンス測定を含む過渡応答測定による拡散係数の決定と単一粒子の等価回路解析,(4)in-situラマン及び導電率測定,さらに上記の測定を(5)室温から高温(50度C)に拡張し,温度特性の評価も行っている。

  23. 有機溶媒中におけるトポケミカル反応場のスペクトロエレクトロケミストリの研究 競争的資金

    1995年4月 ~

︎全件表示 ︎最初の5件までを表示