研究者データベース

八木 一三(ヤギ イチゾウ)
地球環境科学研究院 物質機能科学部門 分子材料化学分野
教授

基本情報

所属

  • 地球環境科学研究院 物質機能科学部門 分子材料化学分野

職名

  • 教授

学位

  • 博士(理学)(北海道大学)

ホームページURL

科研費研究者番号

  • 40292776

ORCID ID

J-Global ID

研究キーワード

  • 人工生体膜反応場   金属酵素修飾電極   電極触媒   エネルギー変換材料   レーザー分光   電気化学   物理化学   Photoelectrochemistry   Interfacial Physical Chemistry   

研究分野

  • 環境・農学 / 化学物質影響 / 硝酸還元反応
  • 自然科学一般 / 生物物理、化学物理、ソフトマターの物理 / 金属酵素の分光電気化学
  • ナノテク・材料 / 機能物性化学
  • ナノテク・材料 / エネルギー化学
  • ナノテク・材料 / ナノ材料科学
  • ナノテク・材料 / 基礎物理化学

職歴

  • 2013年04月 - 現在 北海道大学 大学院地球環境科学研究院 教授
  • 2017年04月 - 2022年03月 理化学研究所 放射光科学総合研究センター 客員研究員
  • 2013年04月 - 2015年03月 技術研究組合FC−Cubic 触媒研究グループ グループ長(兼任)
  • 2010年05月 - 2013年03月 技術研究組合FC−Cubic 触媒研究グループ 研究グループ長
  • 2008年04月 - 2013年03月 理化学研究所 播磨研究所 客員研究員(兼任)
  • 2010年04月 - 2010年04月 産業技術総合研究所 ユビキタスエネルギー研究部門 招聘研究員
  • 2005年07月 - 2010年03月 産業技術総合研究所 固体高分子形燃料電池先端基盤研究センター 研究チーム長
  • 2004年10月 - 2008年03月 科学技術振興機構 「構造機能と計測分析」領域 さきがけ研究員(兼任)
  • 2005年05月 - 2005年06月 北海道大学 大学院理学研究科 助教授
  • 2005年04月 - 2005年06月 産業技術総合研究所 固体高分子形燃料電池先端基盤研究センター 招聘研究員(兼任)
  • 1999年08月 - 2005年04月 北海道大学 大学院理学研究科 講師
  • 2002年10月 - 2003年03月 NIST レーザー応用グループ 客員研究員(兼任)
  • 1997年08月 - 1999年07月 東京大学 大学院工学系研究科 助手
  • 1997年04月 - 1997年07月 日本学術振興会 特別研究員(PD)
  • 1994年04月 - 1997年03月 日本学術振興会 特別研究員(DC1)

学歴

  • 1992年04月 - 1997年03月   北海道大学   大学院理学研究科   化学専攻
  • 1989年10月 - 1992年03月   北海道大学   理学部   化学科
  • 1988年04月 - 1989年09月   北海道大学   教養部   理II系

所属学協会

  • 日本表面真空学会   光化学協会   電気化学会   日本表面科学会   国際電気化学会   触媒学会   米国電気化学会   アメリカ化学会   日本分光学会   日本化学会   

研究活動情報

論文

  • Abinash Chandro Sarker, Masaru Kato, Ichizo Yagi
    Electrochimica Acta 425 140628  2022年09月01日 [査読有り]
     
    We report the preparation of Pt and/or Pd nanoparticle-deposited fluorine-doped tin oxide (FTO) electrodes by an arc-plasma deposition (APD) technique and their electrocatalytic activity for nitrate (NO3–), nitrite (NO2–), nitric oxide (NO), and nitrous oxide (N2O) reduction reactions in acidic media. Cyclic voltammetry of the electrodes revealed that the co-presence of Pt and Pd on FTO showed higher catalytic activity than Pt or Pd on FTO for the NO3– reduction reaction, where the PtPd/Sn interface acts as the catalytic active site. The PtPd/Sn interface also showed higher catalytic activity for the N2O reduction reaction to dinitrogen than the Pt/Sn or Pd/Sn interfaces, whereas it showed no drastic contribution to the electrocatalytic NO2– and NO reduction reactions. Because the NO3– and N2O reduction reaction occur in the potential region of hydrogen adsorption on Pt and Pd electrodes, the PtPd/Sn interface could enhance NO3– and N2O adsorption and/or suppress the hydrogen adsorption. Our findings will be useful for the design of interfaces between noble metal mixture/alloy nanoparticles and Sn, leading to the practical application of denitrification to harmless dinitrogen.
  • Akinobu Yamaguchi, Naoya Akamatsu, Shunya Saegusa, Ryo Nakamura, Yuichi Utsumi, Masaru Kato, Ichizo Yagi, Tomoko Ishihara, Masaki Oura
    RSC Advances 12 17 10425 - 10430 2022年04月 [査読有り]
     
    The electrochemical Ni deposition at a platinum electrode was investigated in a plating nickel bath in the presence and absence of ethylene glycol (EG) using fluorescence yield soft X-ray absorption spectroscopy (FY-XAS) in the Ni L2,3-edge and O K-edge regions under potential control. At ≤+0.35 V vs. the reversible hydrogen electrode (RHE), the electrochemical Ni deposition was detected by the Ni L2,3-edge FY-XAS in the presence of EG whereas almost no such event was observed in the absence of EG. A drastic decrease of FY-XAS intensities in the O K-edge region was also observed in the presence of EG at >+0.35 V vs. RHE, suggesting that the nano-/micro-structured Ni deposition initiated by the removal of water molecules occurs on the Pt electrode. The complex formation of Ni2+ with EG and the adsorption of EG on the Ni surface could play an important role in the Ni deposition. This study demonstrates that the in situ FY-XAS is a powerful and surface-sensitive technique to understand (electro)chemical reactions including polyol synthesis and electrocatalysis at solid-liquid interfaces.
  • Xiao-Fei Gong, Yun-Long Zhang, Lei Zhao, Yun-Kun Dai, Jia-Jun Cai, Bing Liu, Pan Guo, Qing-Yan Zhou, Ichizo Yagi, Zhen-Bo Wang
    Journal of Materials Chemistry A 2022年 [査読有り]
  • Koki Matsumoto, Masaru Kato, Ichizo Yagi, Siqi Xie, Kiyotaka Asakura, Shin-ichiro Noro, Norimitsu Tohnai, Stéphane Campidelli, Takashi Hayashi, Akira Onoda
    28 e202103545  2022年 [査読有り][通常論文]
  • Masaru Kato, Yoshimi Iguchi, Tianchi Li, Yuta Kato, Yu Zhuang, Kotaro Higashi, Tomoya Uruga, Takahiro Saida, Keiko Miyabayashi, Ichizo Yagi
    ACS Catalysis 12 1 259 - 264 2021年12月15日 [査読有り]
  • Satoshi Yasuda, Kazuhisa Tamura, Masaru Kato, Hidehito Asaoka, Ichizo Yagi
    The Journal of Physical Chemistry C 2021年10月04日 [査読有り]
  • Masaru Kato, Yuki Unuma, Manabu Okui, Yunteng Qu, Jinhang Zheng, Satoshi Taguchi, Fumiya Kiguchi, Mashu Torihata, Yunzhi Gao, Nagahiro Hoshi, Ichizo Yagi
    Electrochimica Acta 139281 - 139281 2021年09月 [査読有り]
  • Masaru Kato, Yuya Masuda, Narumi Yoshida, Takehiko Tosha, Yoshitsugu Shiro, Ichizo Yagi
    Electrochimica Acta 373 137888 - 137888 2021年03月 [査読有り]
  • Masaru Kato, Natsuki Fujibayashi, Daiki Abe, Naohiro Matsubara, Satoshi Yasuda, Ichizo Yagi
    ACS Catalysis 2356 - 2365 2021年02月19日 [査読有り]
  • 鵜沼佑規, 奥井学, 田口哲, 加藤優, 加藤優, 八木一三, 八木一三
    表面と真空 64 8 2021年 [査読有り]
  • Masaru Kato, Yukatsu Shichibu, Kazuya Ogura, Mitsuhiro Iwasaki, Mizuho Sugiuchi, Katsuaki Konishi, Ichizo Yagi
    The Journal of Physical Chemistry Letters 11 19 7996 - 8001 2020年10月01日 [査読有り][通常論文]
  • Masaru Kato, Ryota Nakahoshiba, Kazuya Ogura, Shoichi Tokuda, Satoshi Yasuda, Kotaro Higashi, Tomoya Uruga, Yohei Uemura, Ichizo Yagi
    ACS Applied Energy Materials 2020年07月27日 [査読有り][通常論文]
  • Satoshi Yasuda, Kazuhisa Tamura, Tomo O. Terasawa, Masahiro Yano, Hideaki Nakajima, Takahiro Morimoto, Toshiya Okazaki, Ryuushi Agari, Yasufumi Takahashi, Masaru Kato, Ichizo Yagi, Hidehito Asaoka
    Journal of Physical Chemistry C 124 9 5300 - 5307 2020年03月05日 [査読有り][通常論文]
     
    Copyright © 2020 American Chemical Society. Confinement of hydrogen molecules at graphene-substrate interface has presented significant importance from the viewpoints of development of fundamental understanding of two-dimensional material interface and energy storage system. In this study, we investigate H2 confinement at a graphene-Au interface by combining selective proton permeability of graphene and the electrochemical hydrogen evolution reaction (electrochemical HER) method. After HER on a graphene/Au electrode in protonic acidic solution, scanning tunneling microscopy finds that H2 nanobubble structures can be produced between graphene and the Au surface. Defect dependence of the bubble formation suggests that intrinsic defects in graphene, which have high hydrogen permeation barrier but are permeable for protons, are involved in the fundamental mechanism of bubble formation. Strain analysis by Raman spectroscopy also shows that atomic size roughness on the graphene/Au surface originating from the HER-induced strain relaxation of graphene plays significant role in formation of the nucleation site and H2 storage capacity. The result presented herein would provide further understanding of molecular confinement at graphene-based interface and development of novel energy material.
  • Masaru Kato, Ichizo Yagi
    E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 18 81 - 93 2020年03月 
    Polymer electrolyte fuel cells (PEFCs) are a clean, sustainable device to convert chemical energy to electricity and can provide power for automobiles, trains, and ships. In PEFCs, the oxygen reduction reaction (ORR) occurs at the cathode and is catalyzed at electrocatalysts. The activity of ORR electrocatalysts is known to limit the overall performance of PEFCs because the ORR is more sluggish than the hydrogen oxidation reaction at the anode. In the state-of-the-art PEFC, platinum group metal (PGM)-based ORR electrocatalysts are used. Since PGMs are rare and expensive, highly active and durable non-PGM ORR electrocatalysts are required for widespread applications of PEFCs. In nature, metalloenzymes such as cytochrome c oxidase and multicopper oxidases efficiently catalyze the ORR and utilize multinuclear iron and/or copper complexes as active sites. The structure of these active sites and enzyme reaction mechanisms would give us design concepts of artificial non-PGM electrocatalysts for the ORR, possibly leading us to develop next-generation non-PGM electrocatalysts. Herein, recent research progress on understanding enzymatic ORR reaction mechanisms and developing non-PGM ORR electrocatalysts is reviewed from the viewpoint of bio-inspired approaches.
  • Masaru Kato, Keita Kon, Jun Hirayama, Ichizo Yagi
    New Journal of Chemistry 43 25 10087 - 10092 2019年 [査読有り][通常論文]
  • Kato Masaru, Nakagawa Shogo, Tosha Takehiko, Shiro Yoshitsugu, Masuda Yuya, Nakata Kou, Yagi Ichizo
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 9 17 5196 - 5200 2018年09月06日 [査読有り][通常論文]
  • Masaru Kato, Ai Araki, Yuki Hara, Satoshi Taguchi, Ichizo Yagi
    Electrochemistry 86 5 220 - 222 2018年08月 [査読有り][通常論文]
  • Kato Masaru, Ogura Kazuya, Nakagawa Shogo, Tokuda Shoichi, Takahashi Kiyonori, Nakamura Takayoshi, Yagi Ichizo
    ACS OMEGA 3 8 9052 - 9059 2018年08月 [査読有り][通常論文]
     
    Pt-based nanostructured electrocatalysts supported on carbon black have been widely studied for the oxygen reduction reaction (ORR), which occurs at the cathode in polymer electrolyte fuel cells. Because sluggish ORR kinetics are known to govern the cell performance, there is a need to develop highly active and durable electrocatalysts. The ORR activity of Pt-based electrocatalysts can be improved by controlling their morphology and alloying Pt with transition metals such as Ni. Improving the catalyst durability remains challenging and there is a lack of catalyst design concepts and synthetic strategies. We report the enhancement of the ORR activity and durability of a nanostructured Pt-Ni electrocatalyst by strong metal/support interactions with a nitrogen-doped carbon (NC) support. Pt-Ni rhombic dodecahedral nanoframes (NFs) were immobilized on the NC support and showed higher ORR electrocatalytic activity and durability in acidic media than that supported on a nondoped carbon black. Durability tests demonstrated that NF/NC showed almost no activity loss even after 50 000 potential cycles under catalytic conditions, and the Ni dissolution from the NFs was suppressed at the NC support, as confirmed by, energy dispersive X-ray spectroscopy analysis. Physicochemical measurements including surface-enhanced infrared absorption spectroscopy of surface-adsorbed CO revealed that the strong metal/support interactions of the NF with the NC support caused the downshift of the d-band center position of the surface Pt. Our findings demonstrate that tuning the electronic structure of nanostructured Pt alloy electrocatalysts via the strong metal/support interactions with heteroatom-doped carbon supports will allow the development of highly active and robust electrocatalysts.
  • 表面増強赤外吸収分光法による電極/溶液界面における反応計測
    八木一三, 加藤優, 中田耕, 中川省吾
    分光研究 67 2 41 - 56 2018年04月 [査読有り][通常論文]
  • Incorporation of Multinuclear Copper Active Sites into Nitrogen-Doped Graphene for Electrochemical Oxygen Reduction.
    M. Kato, M. Muto, N. Matsubara, Y. Uemura, Y. Wakisaka, T. Yoneuchi, D. Matsumura, T. Ishihara, T. Tokushima, S.-i. Noro, S. Takakusagi, K. Asakura, I. Yagi
    ACS Applied Energy Materials 1 5 2358 - 2364 2018年04月 [査読有り][通常論文]
  • Masaru Kato, Hisako Sato, Ichizo Yagi, Miwa Sugiura
    Electrochimica Acta 264 386 - 392 2018年02月20日 [査読有り][通常論文]
     
    Photosynthesis converts solar energy into chemical energy. Photosystem II (PSII) oxidizes water to produce oxygen, electrons and protons under solar light irradiation. This light-driven water oxidation initiates a series of reactions in photosynthesis. Basic photoelectrochemical studies on PSII are directed toward the enzymatic applications of PSII for sustainable production of electricity or solar fuels. To maximize the photoelectrochemical catalytic activity of PSII on electrode substrates, interfacial designs between PSII and electrode substrates are important. Herein, we report bio-inorganic photoanodes of PSII and ferricyanide-intercalated layered double hydroxide (LDH) for visible-light-driven water oxidation. PSII is simply drop-cast onto a ferricyanide-intercalated cobalt–aluminum LDH and then shows a turnover frequency of 0.5 ± 0.1 s−1 and a turnover number of 920 ± 40 for 1 h at pH 6.5 at +0.5 V vs. NHE under visible light irradiation. Photoelectrochemical experiments using a PSII inhibitor or a bio-engineered PSII suggest that interfacial electron transfer from the plastoquinone QA site of PSII to ferricyanide may play an important role in improving the photo-electrocatalytic activity and stability of PSII. Our studies will open up new possibilities in fundamental or advanced photoelectrochemical studies of PSII.
  • Tomoko Ishihara, Takashi Tokushima, Yuka Horikawa, Masaru Kato, Ichizo Yagi
    REVIEW OF SCIENTIFIC INSTRUMENTS 88 10 2017年10月 [査読有り][通常論文]
     
    We developed a spectro-electrochemical cell for X-ray absorption and X-ray emission spectroscopy, which are element-specific methods to study local electronic structures in the soft X-ray region. In the usual electrochemical measurement setup, the electrode is placed in solution, and the surface/interface region of the electrode is not normally accessible by soft X-rays that have low penetration depth in liquids. To realize soft X-ray observation of electrochemical reactions, a 15-nm-thick Pt layer was deposited on a 150-nm-thick film window with an adhesive 3-nm-thick Ti layer for use as both the working electrode and the separator window between vacuum and a sample liquid under atmospheric pressure. The designed three-electrode electrochemical cell consists of a Pt film on a SiC window, a platinized Pt wire, and a commercial Ag vertical bar AgCl electrode as the working, counter, and reference electrodes, respectively. The functionality of the cell was tested by cyclic voltammetry and X-ray absorption and emission spectroscopy. As a demonstration, the electroplating of Pb on the Pt/SiC membrane window was measured by X-ray absorption and real-time monitoring of fluorescence intensity at the O 1s excitation. Published by AIP Publishing.
  • Masaru Kato, Manabu Okui, Satoshi Taguchi, Ichizo Yagi
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 800 46 - 53 2017年09月 [査読有り][通常論文]
     
    Nitrate anion is one of the main nitrogen-containing-pollutants in groundwater and can be removed" using denitrification systems including electrocatalytic systems. Herein we report on electrocatalytic nitrate reduction catalyzed on tin-modified single crystalline electrodes of palladium, platinum and palladium-platinum alloy in acidic and neutral media. We have prepared electrodes with the (111) surface or the (100) surface and modified their surface with tin. Cyclic voltammetry of the electrodes has revealed that the tin-modified alloy (trimetallic) electrodes show higher electrocatalytic activity than the tin-modified platinum or palladium (bimetallic) electrodes, and the catalytic reaction is more efficiently catalyzed on the (100) surface rather than the (111) surface. The tin-modified PdPt(100) electrode shows the highest catalytic activity in acidic media as well as in neutral media. X-ray photoelectron spectroscopy suggests that metallic tin forms on the (100) surface, but divalent tin species on the (111) surface, indicating that a surface alloy of tin may form on the (100) surface, resulting in enhancement of the electrocatalytic activity. Our findings suggest that design and preparation of ternary metallic electrodes with the (100) surface will pave the way to the development of practical systems on electrocatalytic denitrification. (C) 2017 Elsevier B.V. All rights reserved.
  • 八木一三
    高分子 66 2 65‐66  2017年02月01日 [査読無し][招待有り]
  • Masaru Kato, Takeshi Murotani, Ichizo Yagi
    CHEMISTRY LETTERS 45 10 1213 - 1215 2016年10月 [査読有り][通常論文]
     
    We report an Fe/Cu/N-doped carbon electrocatalyst for the oxygen reduction reaction to water. Pyrolysis of metal precursors supported on oxidized carbon black provides the electrocatalyst with high catalytic activity and selectivity. Detailed physical-chemical studies have revealed that the. copresence of iron and copper catalytic sites in carbon in a 1:1 mole ratio, which is the same as that of an enzyme of cytochrome c oxidase, might be the key to synthesize highly active and selective electrocatalysts.
  • Masaru Kato, Nobuhisa Oyaizu, Katsuaki Shimazu, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 15814 - 15822 2016年07月 [査読有り][通常論文]
     
    We report two-dimensional model systems to study the electrocatalytic activities of dinuclear copper complexes for various electrocatalytic reactions including the oxygen reduction reaction (ORR), where we can use electrochemical techniques as well as surface-sensitive techniques such as X-ray photoelectron spectroscopy and vibrational sum frequency generation spectroscopy. Heteroaromatic thiols, including four triazoles and a thiadiazole, are used as metal ligands as well as anchors to a polycrystalline gold electrode. The thiols are self-assembled on the polycrystalline gold electrode and then react with copper(II) ions to give monolayers of copper-based ORR catalysts on the surface. The dinuclear copper complexes of 1,2,4-triazole-3-thiol and 3-amino-1,2,4-triazole-5-thiol show ORR activity and pH-dependent catalytic behavior similar to that of counterparts supported on carbon black, suggesting that our two-dimensional systems can serve as model catalysts for carbon-supported molecular catalysts. We have also self-assembled dinuclear copper complexes with long alkyl or perfluoroalkyl chains on the surface and studied their orientation on the surface and oxygen transport.
  • Masaru Kato, Ken'ichi Kimijima, Mari Shibata, Hideo Notsu, Kazuya Ogino, Kiyoshi Inokuma, Narumi Ohta, Hiromitsu Uehara, Yohei Uemura, Nobuhisa Oyaizu, Tadashi Ohba, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 14 8638 - 8641 2015年 [査読有り][通常論文]
     
    A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.
  • Ichizo Yagi, Kiyoshi Inokuma, Ken'ichi Kimijima, Hideo Notsu
    JOURNAL OF PHYSICAL CHEMISTRY C 118 45 26182 - 26190 2014年11月 [査読有り][通常論文]
     
    Perfluorosulfonated ionomer (PFSI), such as Nafion, in polymer electrolyte fuel cells (PEFCs) has been recognized as an important component to shuttle protons during the electrocatalytic reactions, especially the oxygen reduction reaction (ORR) at the cathode. However, a molecular structure of PFSIs inside catalyst layers in PEFCs has been unclear, since the polymers surrounding the gas-diffusion electrode with meso-to-macroporous structures have been considered to be much more complicated to resolve. Recent progress in the environmental electron microscopic technology clarified the real thickness of PFSI films to be only several nanometers, which can be analyzed by spectroscopic techniques and simulation modelings with molecular insights. Infrared and Raman spectroscopies were promptly applied to obtain the molecular arrangement of Nafion on the surface of Pt catalysts, but the thicknesses of the Nafion films seemed to be much thicker than the real thicknesses of PFSI in catalyst layers. In the present study, the preparation method of an ultrathin film of Nafion on Pt surface with <1 nm thickness was established and the vibrational sum frequency generation (VSFG) spectroscopy, which is an inherently surface-selective method, was applied to extract the interfacial molecular structure even at relatively thick Nafion films on Pt surfaces. By comparing thickness dependencies of IR and VSFG spectra, the molecular arrangement of Nafion at buried Nafion/Pt interface was confirmed to adsorb via sulfonate terminals of side-chains.
  • Ichizo Yagi, Kensuke Mikami, Masayuki Okamura, Kohei Uosaki
    CHEMPHYSCHEM 14 10 2174 - 2182 2013年07月 [査読有り][通常論文]
     
    The ultrafast dynamics of photogenerated electrons in multilayer assemblies of CdS nanoparticles prepared on quartz and indium-tin oxide (ITO) substrates were followed by femtosecond (fs) visible-pump/mid-IR probe spectroscopy. Based on the observation of the photoinduced transient absorption spectra in the broad mid-IR range at the multilayer assembly of CdS nanoparticles, the occupation and fast relaxation of higher electronic states (1P(e)) were clarified. As compared with the electron dynamics of isolated (dispersed in solution) nanoparticles, the decay of photoexcited electrons in the multilayer assembly was clearly accelerated probably due to both electron hopping and scattering during interparticle electron tunneling. By using an ITO electrode as a substrate, the effect of the electric field on the photoelectron dynamics in the multilayer assembly was also investigated in situ. Both the amplitude and lifetime of photoexcited electrons gradually reduced as the potential became more positive. This result was explained by considering the reduction of the interparticle tunneling probability and the increase in the electron-transfer rate from the CdS nanoparticle assembly to the ITO electrode.
  • Xiaojing Zhao, Akari Hayashi, Zhiyun Noda, Ken'ichi Kimijima, Ichizo Yagi, Kazunari Sasaki
    ELECTROCHIMICA ACTA 97 33 - 41 2013年05月 [査読有り][通常論文]
     
    Carbon supports of electrocatalysts for polymer electrolyte fuel cells were heat treated with the aim of proposing carbon materials with high corrosion resistance and with the sufficient nanostructure to interact with platinum particles, simultaneously. Two kinds of commercially available state-of-the-art carbon black materials, Vulcan XC-72 and Ketjen Black EC600-JD, were heat treated at 1100, 1600, and 2000 degrees C in order to produce the graphitized surface. Eight different Pt/C catalysts were synthesized, and their durability was examined using an electrochemically accelerating potential cycle protocol, considering a practical condition of fuel cell vehicles. Their durability was evaluated through the change in electrochemically active surface area, oxygen reduction reactivity, and platinum particles in TEM images. As expected, higher graphitization degree lead to increasing in corrosion resistance, but at the same time resulted in reducing the immobilization ability of platinum on carbon supports. Therefore, an optimum condition with both high corrosion resistance and sufficient interaction with platinum particles was investigated. Consequently, in this study we have found graphitization at 1600 degrees C is an optimum temperature among 1100, 1600, and 2000 degrees C to obtain highest durability for Pt/C catalysts, and the graphitization degree is an important factor to develop catalysts with high durability. (C) 2013 Elsevier Ltd. All rights reserved.
  • I. Yagi, K. Inokuma, N. Ohta
    FULLERENES, NANOTUBES, AND CARBON NANOSTRUCTURES - 221ST ECS MEETING 45 20 103 - 109 2013年 [査読有り][通常論文]
     
    Focusing the void plasmon toward the rim part of the sphere segment void (SSV) type plasmonic crystalline structures are further developed by retaining the polystyrene nanospheres inside the voids. Plasmonic whispering gallery modes (WGMs) are proved to appear in such the hybrid structures by the measurements of reflectance spectroscopy and cause the improvement of signal/background ratio in the SERS spectra. From the detailed experimental analyses, a possibility of the plasmonic WGMs to enhance the molecular signal at the Pt electrode surfaces is shown.
  • Tamio Ikeshoji, Minoru Otani, Ikutaro Hamada, Osamu Sugino, Yoshitada Morikawa, Yasuharu Okamoto, Yumin Qian, Ichizo Yagi
    AIP ADVANCES 2 3 2012年09月 [査読有り][通常論文]
     
    The charged interface between a platinum electrode and an aqueous solution is investigated by first-principles molecular dynamics simulations in which charges in the system are controlled by the effective screening medium method under periodic boundary conditions. H3O+ and OH are located above or on the Pt surface. Water molecules rotate to screen the electric field induced by the charge accumulated on the Pt surface. The time-averaged electrostatic potential near the Pt surface is structured with a flattened "bulk" region. The potential difference between the Pt Fermi level and the bulk potential is proportional to the charge and is used to estimate the Pt electrode potential via the PZC (potential of the zero charge). The surface charge significantly polarizes the water molecules near the Pt surface. The OH stretching frequency of molecules on the negatively charged (7 similar to 14 mu C/cm(2)) Pt electrode shift to lower values (red shift) by 100 similar to 200 cm(-1). For the positively charged Pt lattice, a complex feature results from a charge transfer reaction that takes place there. The electrode structure is also influenced by accumulated charge as the distance between the top surface Pt layer and the next layer underneath increases for both the negatively and positively charged surfaces. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4756035]
  • Narumi Ohta, Kamba Nomura, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 116 27 14390 - 14400 2012年07月 [査読有り][通常論文]
     
    Surface-enhanced infrared absorption spectroscopy was applied to the in situ observations of the surface. intermediates during the oxygen reduction reaction (ORR) on quasi-Au(111) thin-film electrode surfaces in contact with 0.5 M perchloric acid aqueous solutions. The spectroscopy revealed the presence of adsorbed molecular oxygen (O-2(ads)) and hydrogen superoxide (HO2(ads)) during the reaction. These species are not present on the surfaces exposed to the solutions containing no dissolved O-2. In addition, coupled to the onset of the reaction current for the ORE, the surface coverages of the O-2(ads) and the HO2(ads) showed an abrupt decrease and increase, respectively. These results constitute the first spectroscopic evidence of the proton coupled one electron electroreduction of the O-2(ads) to form the HO2(ads), which has been postulated to occur during the ORR on Au surfaces in acidic media. In addition, the spectroscopy provided for the first time detailed information regarding the structure of the ionic and molecular species formed on the electrode surface in which the O-2(ads) is present; that is, the O-2 hydrated with water molecules is preferentially adsorbed onto the surfaces over the perchlorate anions.
  • A. Hayashi, I. Yagi, K. Kimijima, K. Sasaki
    ECS Transactions 41 19 15 - 23 2012年 [査読無し][通常論文]
     
    For the purpose of studying electrochemical reactions in nanospace of structurally controlled carbon, electrochemistry inside the hydrophobic 8 nm pores with platinum deposited mesoporous carbon (Pt/MC) was investigated, and reaction selectivity within carbon nano-space was demonstrated. Distinctive activities toward hydrogen evolution/oxidation and oxygen evolution reactions were observed, comparing to reactions in larger pores (> 30 nm). Only small amount of water is expected to exist within such small nano-space even though a proton pass is effectively maintained. Consequently, selectivity in reactions, such as activation of proton-related reactions and suppression of water-related reactions, is achieved by Pt/MC electrocalatysts. ©The Electrochemical Society.
  • Toshihiro Kondo, Chunli Song, Naoko Hayashi, Takara Sakurai, Masayo Shibata, Hideo Notsu, Ichizo Yagi
    CHEMISTRY LETTERS 40 11 1235 - 1237 2011年11月 [査読有り][通常論文]
     
    Electrocatalytic activity for oxygen reduction reaction (ORR) of pseudomorphic Pt monolayer prepared electrochemically on a Au(111) surface was investigated and compared with that of a single-crystal Pt(111) electrode.
  • Takara Sakurai, Masayo Shibata, Reiko Horiuchi, Ichizo Yagi, Toshihiro Kondo
    CHEMISTRY LETTERS 40 4 402 - 404 2011年04月 [査読有り][通常論文]
     
    Platinum (Pt) dissolution during oxidation/reduction cycle in various potential cycle ranges and in various pHs of the oxygen-saturated and deaerated H2SO4 and HClO4 electrolyte solutions was monitored by the highly sensitive electrochemical quartz crystal microbalance (EQCM) system. It was found that the Pt mass reduction depended on the potential cycle range and pH of the electrolyte solution with dissolved oxygen. Based on these results, it can be suggested that the dissolution of Pt requires one proton per one Pt and that it also requires dissolved oxygen, and then we can conclude that the dissolution reaction of Pt is as followings; PtO + H+ + 1/2O(2) + H2O -> Pt(OH)(3)(+) and/or PtOH + H+ + 3/4O(2) + 1/2H(2)O -> Pt(OH)(3)(+).
  • I. Yagi, N. Ohta, K. Inokuma
    FULLERENES, NANOTUBES, AND CARBON NANOSTRUCTURES - 219TH ECS MEETING 35 25 183 - 191 2011年 [査読有り][通常論文]
     
    Two dimensional plasmonic structures provide rigid and stable SERS-active substrate. For example, sphere segment void (SSV) structure seems to be attractive, since this structure can be prepared only by wet chemistry and the SERS enhancement coupled with various plasmon modes is available. On the other hand, the SERS-active sites become unclear from the contribution of various plasmon modes and the distribution of them should be understood to investigate the electrocatalytic reactions with in situ electrochemical SERS measurements. In this study, the localization of SERS-active sites in Au-SSV and the focusing the plasmon field to different metals are investigated.
  • I. Yagi, K. Nomura, H. Notsu, K. Kimijima, N. Ohta
    POLYMER ELECTROLYTE FUEL CELLS 11 41 1 689 - 696 2011年 [査読有り][通常論文]
     
    The role of ionomer inside catalyst layers of polymer electrolyte fuel cell (PEFC) are much interested to understand the reaction mechanism and to optimize the structure of catalyst layer in the molecular scale. Electrochemical and spectroscopic investigations are performed in perfluoroalkylsulfonic acid electrolyte as models for side-chain of Nafion ionomers. Specific adsorption of Nafion side chain model anion is observed both at Pt(111) and Au(111)-like electrodes. The effect of perfluoroalkyl chain length seems clearer at Au(111)-like electrode than at Pt(111) and monitored by in situ SEIRA spectroscopy.
  • Narumi Ohta, Kamba Nomura, Ichizo Yagi
    LANGMUIR 26 23 18097 - 18104 2010年12月 [査読有り][通常論文]
     
    Surface-enhanced infrared absorption (SEIRA)-active Au/Ti bilayer films sputter deposited on Si substrates have been prepared by an electrochemical annealing (ECA) treatment for the first time. The application of Au/Ti bilayer films on Si substrates to the spectroscopic technique is a promising alternative to the conventional technique using directly deposited Au films on Si substrates, offering excellent adhesive durability of the deposited metal films. However, Au/Ti bilayer films have never been selected for the spectroscopy technique because the films in the as-prepared state exhibit relatively smooth surface morphology: the excitation of the localized surface plasmon is vital to achieving SEIRA enhancements but could hardly be observed on the smooth morphology. It is shown by ex situ scanning tunneling microscopy measurements that the unfavorable smooth morphology of the as-prepared Au/Ti bilayer films can be modified by the ECA treatment to a reasonably rough, island-structure morphology similar to that of the conventional SEIRA-active Au films. In situ infrared absorption spectroscopy of adsorbed sulfate anions has been conducted on the Au/Ti bilayer film both before and after ECA treatment. The spectroscopy measurements demonstrate that the SEIRA activity of the film after being subjected to the treatment is significantly improved so that the technique could detect adsorbates on the film electrodes even with the submonolayer coverage. As an additional benefit, the ECA treatment has brought about a substantial increase in the fraction of Au(111) domains on the polycrystalline Au film surfaces. Accordingly, this approach enables us to prepare SEIRA-active Au films having sufficient adhesion to the Si substrates as well as the highly preferred (111) orientation.
  • Ken'ichi Kimijima, Akari Hayashi, Shun Umemura, Junichi Miyamoto, Koshi Sekizawa, Toshihiko Yoshida, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 114 35 14675 - 14683 2010年09月 [査読有り][通常論文]
     
    Novel model catalysts to characterize the structural factors related to the activity of the oxygen reduction reaction (ORR) at the thin film electrode of elcctrocatalysts were proposed. Model catalysts were constructed of mesoporous carbon aerogels (CAGs) and ionomers of various molecular weights in order to estimate the effect of the nanostructure of the catalysts or catalyst layers on their ORR activity. The ORR kinetics of the Pt-deposited mesoporous CAG catalysts clearly depended on their pore sizes in the supports, and the smaller pore size resulted in a lower kinetic current for the ORR. However, the ORR kinetics even for the Pt-deposited CAG catalyst with the smallest pores (similar to 7 nm) was improved by the addition of an ionomer with a much lower molecular weight than Nafion, compared to that of the commercially available catalyst without rigid mesopores. These results indicated that the introduction of ionomers in the catalyst layer was a key to increasing the utility of a platinum catalyst and to develop a novel design of nanostructured catalyst layers.
  • Ichizo Yagi, Akari Hayashi, Ken'ichi Kimijima, Hideo Notsu, Narumi Ohta, Akira Yamaguchi
    ELECTROCHEMISTRY 78 2 105 - 113 2010年02月 [査読有り][招待有り]
     
    Construction of nanomaterials has been developed from both top-down and bottom-up approaches. In these approaches, surfactant-templated mesoporous materials are promising because of their tunability, uniformity and reproducibility in both the size and shape of produced mesopores. Mesoporous silica materials have been widely and deeply investigated in the early stage, basing on the sol-gel chemistry of silicate. Although insulating mesoporous silica cannot be directly applicable to electrode materials, the mesoporous silica films and their hybrid films are recently applied as hard templates and electrodeposition of metals inside the mesopores realizes the formation of metal nanowire assembly, which has parallel orientation to the electrode surface. Furthermore, the mesoporous silica film with perpendicularly oriented mesochannels are prepared and used as hard-template, resulting in the fabrication of metal nanowire assembly standing on the electrode surface. On the other hand, conductive materials are recently fabricated as mesoporous structure by the surfactant-template method. Mesoporous carbon becomes the most conventional mesoporous conductive material and has been investigated as the electrode material mainly applicable to energy conversion. By introducing catalyst particles and ionomers inside mesochannels, triple phase boundary can be constructed and the application toward cathode electrode in the polymer electrolyte fuel cell (PEFC) has been investigated.
  • Narumi Ohta, Kiyoshi Inokuma, Keiko Miyabayashi, Mikio Miyake, Ichizo Yagi
    ELECTROCHEMISTRY 78 2 132 - 135 2010年02月 [査読有り][通常論文]
     
    Cubic-shaped Pt nanoparticles have been deposited on carbon fiber (CF) electrode surfaces directly by two electrochemical techniques, namely, potential cycling and stepping in an aqueous solution of 1 mM K2PtCl4 and 0.1 M H2SO4 containing I mM NaI. It is shown that both nucleation and growth processes of the Pt phase formation on the CF surfaces were extensively suppressed by the strong interaction between Pt surface and I- anions. Consequently, this has lead to the formation of the highly dispersed preferentially cubic-shaped Pt nanoparticles.
  • I. Yagi, K. Nomura, H. Notsu, K. Kimijima, A. Hayashi, N. Ohta
    FULLERENES, NANOTUBES, AND CARBON NANOSTRUCTURES - 217TH ECS MEETING 28 17 111 - 120 2010年 [査読有り][通常論文]
     
    The electrochemical annealing of very flat Au thin film with adhesive Ti layer can modify its morphology to an island-like film, which is favorable for spectroscopies with the surface enhanced infrared absorption (SEIRA) method. The nanostructured Au/Ti bilayer can be also useful to detect adsorbates on commercial or developed catalysts deposited on its surface.
  • Akari Hayashi, Ken’ichi Kimijima, Ichizo Yagi
    Advances in Nanotechnology. Volume 2 325 - 346 2010年01月01日 [査読有り][通常論文]
     
    © 2010 Nova Science Publishers, Inc. Mesoporous materials are attractive because of their highly controllable ordered pore structure, and they are possibly used as catalytic nanoreactors if catalysts are successfully deposited within the pores. Among those mesoporous materials, mesoporous carbon (MC) materials were chosen owing to their high electric conductivity, and Pt was deposited inside the pores in order to apply for electrode materials. MC materials are commonly synthesized using mesoporous silica template, but the resulting pores are 2-3 nm sized and probably not large enough to deposit catalyst particles in the pores. Here, MC with relatively large pores was synthesized through self-organization of a surfactant and carbon precursors followed by carbonization. The obtained MC had 7-8 nm sized pores, and Pt nanoparticles were deposited inside the pores of MC by addition of Pt cations followed by reduction to metal Pt. The size and dispersion of Pt nanoparticles depended on the starting Pt precursors, but well dispersion of 1 nm or smaller Pt nanoparticles inside the pores was obtained without sintering. The properties as cathode of polymer electrolyte fuel cell were examined. To do so, Nafion® should also be introduced to mespores. Developing of an ideal triple phase boundary by introducing catalyst nanoparticles and ionomers into the pores and further building up the nanoreactor array were expected. When oxygen reduction reactivity with Pt deposited MC (Pt/MC) thin film rotating disk electrode was examined, the addition of Nafion® lead to increase in oxygen reduction reaction (ORR) current comparing to that without Nafion®. Therefore, a triple phase boundary was successfully developed inside the pores. Oxygen reduction reactivity depended on which Pt precursors were in use or how easily Nafion® could access to the pores. When Nafion® was dispersed in more hydrophobic solvent, Nafion® was more easily accessible to the pores, and as a result, higher ORR current was obtained. Furthermore, ORR current at Pt/MC thin film rotating disk electrode appeared to be not under control of oxygen diffusion from the electrolyte solution in the region where Pt/CB thin film rotating disk electrode showed the diffusion limited current. Then, oxygen transfer and storage processes within the pores were investigated, and the process was a characteristic function of Pt/MC. Mesopores can produce a channel connecting catalysts and external environment and favorably transferring oxygen, and oxygen is diffused through Nafion® inside the pores.
  • Ken'Ichi Kimijima, Akari Hayashi, Ichizo Yagi
    ACS National Meeting Book of Abstracts 2009年12月01日 [査読無し][通常論文]
     
    A nano-scale structure of catalyst layer (electrode) of PEFC (polymer electrolyte membrane fuel cell) seems to be one of important factors for its performance, since the formation of effective reaction sites and the mass transfer of reactant are governed by the pore structure. In order to evaluate the pore structure, a model electrode was made by using mesoporous carbon membrane which with controlled pore structure. In this report, we show that preparation of a model electrode and electrochemical analysis.
  • Akari Hayashi, Ken'ichi Kimijima, Junichi Miyamoto, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 113 28 12149 - 12153 2009年07月 [査読有り][通常論文]
     
    Platinum-deposited mesoporous carbon (Pt/MC) catalyst has revealed an interesting response toward oxygen reduction. Its thin-layer rotating disk electrode (RDE) has shown characteristic oxygen reduction Current that does not depend oil oxygen diffusion through the electrolyte solution, while Pt-deposited carbon black (Pt/CB) thin-layer RDE shows diffusion-limited current. This is due to unique oxygen transfer and storage occurring within the 7-8 nm sized mesopores of MC support, which do not exist in CB support. With a Pt/MC thin-layer electrode, mesopores can produce in ionomer-filled channel connecting catalysts and external environment and favorably transferring oxygen. Also, even after oxygen inside the pores is used up, oxygen call be restored during the potential cycling.
  • Akari Hayashi, Ken'ichi Kimijima, Junichi Miyamoto, Ichizo Yagi
    CHEMISTRY LETTERS 38 4 346 - 347 2009年04月 [査読有り][通常論文]
     
    Pt nanoparticles were deposited on mesoporous carbon support using two different Pt precursors, and the difference in mass activity toward oxygen reduction between the two was successfully examined through direct observation of Pt nanoparticles inside the mesopores. Existence of 1-nni-sized Pt particles on the wall of mesopores was observed, and catalytic activity was hi-her if the size of Pt particles inside the pores was smaller. The size and stability of Pt catalysts encapsulated in nanospace is key for catalytic activity.
  • 林直子, 野津英男, 八木一三, 近藤敏啓
    表面科学 30 9 499-502 (J-STAGE)  2009年 [査読無し][通常論文]
  • Narumi Ohta, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 112 45 17603 - 17610 2008年11月 [査読有り][通常論文]
     
    The work presented here describes the first steps toward designing a planar surface-enhanced Raman scattering (SERS)-active electrode surface, instead of randomly roughened electrode surfaces conventionally used, with the potential to conduct in situ monitoring of electrochemical and electrocatalytic reactions. A planar and preferentially (111) orientated Au film sputtered on a micropatterned Si surface consisting of a square lattice of inverted pyramidal pits has been prepared to generate high-quality SERS signals at 785 nm excitation wavelength and is applied to detect the orientational phase transition of adsorbed pyridine (Py) in aqueous solution. We have successfully obtained the potential-dependent frequency shift of the totally symmetric ring-breathing mode (v(1)) of Py adsorbed on the Au electrode surface from 1015 to 1011 cm(-1) as the electrode potential is successively changed from 0.84 to -0.06 V vs RHE, tracking the orientational phase transition of the adsorbate from almost end-on fashion at positive potentials to an almost flat-on orientation at negative potentials. This result indicates the possibility of the sensitivity of SERS on the planar Au surfaces, down to the submonolayer molecular adsorbate level. In addition, the good reversibility of the frequency shift of the v(1) mode observed during the continued positive-going potential sweep proves the planar Au surface and the Au-coated micropatterned structure are stable in the practical electrochemical condition.
  • 八木 一三
    表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 29 9 518 - 525 日本表面科学会 2008年09月10日 [査読有り][招待有り]
     
    Two-dimensional chirality has attracted interest as an approach to develop novel chiral catalysts and sensors. However, there is no standard tool to distinguish and evaluate the chirality at surfaces and interfaces, since the number of chiral molecules or chiral sites are limited in the two-dimensional system. Linear chiroptical spectroscopy, such as circular dichroism (CD) and Raman optical activity (ROA), cannot be applied to the two dimensional system, because these methods are basing on the optical transition forbidden under the electric dipole approximation and, then, the chiral responses becomes much weak. Recently, one of the nonlinear spectroscopy, infrared-visible sum frequency generation (VSFG) has been established as a novel chiroptical tool to investigate the molecular and surface chirality. In the present study, this optical technique was applied to recognize the chirality at chiral molecules-modified surfaces under the nonelectronic resonant condition. For polycrystalline films of bi-naphthol (BINOL), chiral VSFG signal reached around 50% of achiral SFG signal and the chirality of the thin film could be successfully recognized. On the other hand, for submonolayer of binaphthyl molecules on Au, there was a limitation in the sensitivity and it was desired to introduce the doubly resonant VSFG enhancement for in situ monitoring of chiral recognition processes.
  • Akari Hayashi, Hideo Notsu, Ken'ichi Kimijima, Junichi Miyamoto, Ichizo Yagi
    ELECTROCHIMICA ACTA 53 21 6117 - 6125 2008年09月 [査読有り][通常論文]
     
    Highly structurally controllable mesoporous carbon (MC) support was synthesized through the self-organization of surfactants and carbon precursors, followed by carbonization. Then, Pt catalysts were successfully deposited on MC, in order to create a model of an ideal triple phase boundary in such a nano-space. The resulting Pt/MC catalysts showed better oxygen reduction reactivity with the existence of Nafion (R) than without that. Handling of ionomers is a key to develop an ideal triple phase boundary within the pores of MC. Depending on the solvent where Nafion (R) was diluted, the reactivity toward oxygen reduction was different. Due to its hydrophobic pores of MC, Nation (R) diluted by more hydrophobic solvent was able to access to the pores easily. As a result, Pt inside the mesopores was efficiently used. Furthermore, by changing a Pt precursor, oxygen reduction current started to increase at more positive potential, indicating the enhanced activity. (C) 2008 Elsevier Ltd. All rights reserved.
  • 八木 一三
    電気化学および工業物理化学 : denki kagaku 76 3 220 - 226 電気化学会 2008年03月05日 [査読無し][招待有り]
  • Ken'ichi Kimijima, Akari Hayashi, Ichizo Yagi
    CHEMICAL COMMUNICATIONS 44 5809 - 5811 2008年 [査読有り][通常論文]
     
    A self-standing mesoporous carbon membrane (sOMC) with perpendicularly-ordered pore structures was prepared through a simple synthetic method; the pores with a diameter of 8 nm were well ordered over a large area and perpendicularly-oriented to the surface without any external field; in the formation of this ordered structure, the drying process is key, and a porous alumina support is important to induce drying.
  • Minori Taguchi, Ichizo Yagi, Masaru Nakagawa, Tomokazu Iyoda, Yasuaki Einaga
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 33 10978 - 10982 2006年08月 [査読有り][通常論文]
     
    The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices.
  • Ichizo Yagi, Kensuke Mikami, Kojiro Ebina, Masayuki Okamura, Kohei Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY B 110 29 14192 - 14197 2006年07月 [査読有り][通常論文]
     
    Ultrafast photoexcited carrier dynamics in CdS nanoparticles prepared by an AOT/n-heptane reversed micelle system were investigated by a femtosecond visible-pump/mid-IR probe technique. A mid-IR probe beam was found to mainly probe the ultrafast dynamics of photoexcited electrons in the conduction band. Dispersions of CdS nanoparticles with 8 different mean diameters from 2.9 to 4.1 nm were prepared by tuning the mole ratio between water and AOT (W = [H2O]/[AOT]) in the reversed micelle systems. The excited state lifetime strongly depended on the mean size of CdS nanoparticles with a maximum around a mean diameter of 3.5 nm. This result was explained by considering the balance between the carrier recombination rates via surface states and those via interior states. The relationship between the excited state lifetime and the size of CdS nanoparticles was drastically changed when the surface was terminated by thiol molecules.
  • Yagi, I, M Chiba, K Uosaki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 36 12743 - 12746 2005年09月 [査読有り][通常論文]
     
    Two-dimensional chirality at naturally chiral gold single crystalline surfaces was detected and characterized using optical second harmonic generation (SHG) measurements. SHG rotational anisotropy (SH-RA) patterns at Au(643)(S) and Au(643)(R) surfaces were mirror symmetric to each other. Systematic SH-RA measurements at chiral Au(hkl) surfaces with the same step and kink structures but different (111) terrace widths showed a linear correlation between surface step density and SH-RA fitting parameters arising from defects. These results indicate that SH-RA measurements provide information not only on surface chirality but also on density of surface defects.
  • 八木 一三, 魚崎 浩平
    光化学 = Photochemistry 36 1 2 - 9 光化学協会 2005年05月12日 [査読無し][通常論文]
  • Yagi, I, S Idojiri, T Awatani, K Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY B 109 11 5021 - 5032 2005年03月 [査読有り][通常論文]
     
    In situ optical second harmonic generation (SHG) technique was employed to investigate the shape and density of Cu nanoclusters, which were electrochemically formed on p-GaAs(001) electrode surfaces. Since GaAs is not a centrosymmetric medium, a significant portion of SHG signal arises from the bulk dipole susceptibility, but it was possible to separate a surface-induced signal from a bulk-induced signal by choosing an appropriate experimental geometry and appropriate data processing. The rotational anisotropy (RA) pattern of the SHG signal from a p-GaAs(001) electrode changed in both shape and magnitude during potential cycling in an electrolyte solution containing Cu2+. The surface plasmon-induced SHG signal from Cu nanoclusters deposited on GaAs was attributed to the modulation source for the RA-SHG pattern. More detailed study was carried out with both in situ SHG and ex situ AFM measurements for Cu nanoclusters deposited by potential step. The results showed that the SHG signal at the present optical geometry was sensitive to the number of oblate or flattened Cu nanoclusters with lateral diameter larger than 30 nm and that the SHG enhancement occurred because of resonant coupling between the surface plasmon induced in the flattened Cu nanoclusters and the near-infrared fundamental light.
  • Yagi, I, T Ishida, K Uosaki
    ELECTROCHEMISTRY COMMUNICATIONS 6 8 773 - 779 2004年08月 [査読有り][通常論文]
     
    Electrocatalytic reduction of oxygen at a boron (B)-doped diamond (BDD) electrode on which Au nanoclusters (GNCs) were deposited by vacuum-evaporation was investigated in 50 mM H2SO4 solution. Oxygen reduction current started to flow at a more positive potential at the GNCs/BDD electrode than at a polycrystalline gold electrode. Formation of water through a 4-electron reduction pathway at the GNCs/BDD electrode was confirmed, although oxygen reduction at gold electrodes in acidic solutions generally proceeds via a 2-electron pathway generating H2O2. (C) 2004 Published by Elsevier B.V.
  • H Koshima, H Miyamoto, Yagi, I, K Uosaki
    CRYSTAL GROWTH & DESIGN 4 4 807 - 811 2004年07月 [査読有り][通常論文]
     
    Noncentrosymmetic and chiral cocrystals were prepared from 2-amino-3-nitropyridine (2A3NP) and achiral benzenesulfonic acids (Ar-SO3H), which were designed for second-order nonlinear optical materials. Both components are commonly crystallized in 1:1 ionic forms of 2A3NPH(+)-Ar-SO3-. The molecular packings of cocrystals are controlled by the aromatic-aromatic interactions as well as multidirectional ionic and hydrogen bonds between the 2A3NPH(+) cations and the sulfonate anions. The crystal of 2A3NP with p-toluenesulfonic acid belongs to acentric space group Pna2(1), in which 2A3NPH(+) cations and anions are alternately stacked with some dihedral angle due to the large sulfonate anions to form two independent column structures in a perpendicular direction to each other. The crystal of 2A3NP with p-nitrobenzenesulfonic acid crystallizes into chiral space group P2(1)2(1)2(1). The 2A3NPH(+) cations and the anions are also alternately stacked to give herringbone network of 2A3NPH(+) cations. The crystal of 2A3NP with 2,5-dimethylbenzenesulfonic acid belongs to acentric space group Pn, in which two independent stacking structures are formed in perpendicular directions. Second-harmonic generation (SHG) power measured with an evanescent wave technique revealed the relatively high SHG efficiency of cocrystal of 2A3NP with p-toluenesulfonic acid, 2-fold larger than that of well-known m-nitroaniline.
  • K Ebina, Yagi, I, H Noguchi, K Uosaki
    CHEMISTRY LETTERS 33 5 604 - 605 2004年05月 [査読有り][通常論文]
     
    The femtosecond visible pump mid-IR probe technique was employed to investigate photogenerated carrier dynamics in n-GaAs (100) crystals Subjected to various surface treatments in a time domain of picoseconds-several tens of picoseconds. Pt- or Ru-treatment significantly accelerated the carrier recombination as a result of the introduction of surface states. The recombination rate was also increased by Au-treatment but less significantly than that by the Pt- or Ru-treatment. The effect of sulfide treatment on the recombination dynamics seemed to be rather small, although it has been reported that the density of Surface states is decreased by the Sulfide treatment.
  • Hideko Koshima, Hironori Miyamoto, Ichizo Yagi, Kohei Uosaki
    Molecular Crystals and Liquid Crystals 414 77 - 86 2004年 [査読有り][通常論文]
     
    Cocrystals were prepared from 2-amino-5-nitropyridine (2A5NP) and achiral benzenesulfonic acids (Ar-SO3H), which were designed for second-order nonlinear optical materials. Both components are commonly crystallized in 1:1 ionic forms of 2A5NPH+̇Ar-SO3 -, The cocrystal of 2A5NP with 2-nitrobenzenesulfonic acid belongs to acentric space group Pc, in which 2A5NPH+ cation and anion are alternately stacked in an almost parallel and superimposed manner to form column and layer structures. The cocrystal of 2A5NP with 3-nitrobenzenesulfonic acid is crystallized into chiral space group P21212 1. The 2A5NPH+ cation and anion are also alternately stacked with some dihedral angle to form column structures. These organic-organic cocrystals are controlled by the aromatic-aromatic interactions as well as multidirectional ionic and hydrogen bondings between the 2A5NPH + cations and Ar -SO3- anions. Second-harmonic generation (SHG) powers of the crystals measured by second-harmonic generation with evanescent wave (SHEW) technique were, however, smaller than that of area. The reasons for small SHG powers are discussed based on the molecular arrangements.
  • H Koshima, H Miyamoto, Yagi, I, K Uosaki
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 414 77 - 86 2004年 [査読有り][通常論文]
     
    Cocrystals were prepared from 2-amino-5-nitropyridine (2A5NP) and achiral benzenesulfonic acids (Ar-SO3H), which were designed for second-order nonlinear optical materials. Both components are commonly crystallized in 1:1 ionic forms of 2A5NPH(+).Ar-SO3-. The cocrystal of 2A5NP with 2-nitrobenzenesulfonic acid belongs to acentric space group Pc, in which 2A5NPH(+) cation and anion are alternately stacked in an almost parallel and superimposed manner to form column and layer structures. The cocrystal of 2A5NP with 3-nitrobenzenesulfonic acid is crystallized into chiral space group P2(1)2(1)2(1). The 2A5NPH(+) cation and anion are also alternately stacked with some dihedral angle to form column structures. These organic-organic cocrystals are controlled by the aromatic-aromatic interactions as well as multidirectional ionic and hydrogen bondings between the 2A5NPH(+) cations and Ar-SO3- anions. Second-harmonic generation (SHG) powers of the crystals measured by second-harmonic generation with evanescent wave (SHEW) technique were, however, smaller than that of area. The reasons for small SHG powers are discussed based on the molecular arrangements.
  • Yagi, I, T Awatani, T Kondo, K Hanaoka, J Morita, S Takakusagi, K Tamura, M Takahasi, J Mizuki, K Uosaki
    SURFACE OXIDE FILMS 2003 25 143 - 150 2004年 [査読有り][通常論文]
     
    Electrochemical oxide layer formation and reduction processes at single crystalline Au(100) and Au(111) surfaces were investigated by optical second harmonic generation (SHG) and surface X-ray scattering (SXS) techniques. SH signal response under 600 nm excitation wavelength at highly ordered Au(100) and Au(111) single crystalline surfaces were totally different. At the Au(100) electrode, the SH signal under 600 nm excitations increased upon the formation of highly oxidized surface. This response was essentially the same as those at polycrystalline Au electrode surfaces. At the Au(111) electrode, however, the SH signal excited by 600 nm showed essentially no change within the oxide formation/reduction region. On the other hand, the SXS results have indicated that the rate of incorporation of oxygen species into the low-lying Au layers was higher at the Au(100) than at the Au(111) surfaces. These results were explained in terms of the kinetically controlled formations of different kinds of Au oxides at each surface.
  • H Koshima, H Miyamoto, Yagi, I, K Uosaki
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 420 79 - 89 2004年 [査読有り][通常論文]
     
    Cocrystals were prepared from 2-amino-5-nitropyridine ( 2A5NP) and achiral benzenesulfonic acids (Ar-SO3H), which were designed for second-order nonlinear optical materials. Both components are commonly crystallized in 1: 1 ionic forms of 2A5NPH+.Ar-SO3-. The cocrystal of 2A5NP with 2-nitrobenzenesulfonic acid belongs to acentric space group Pc, in which 2A5NPH(+) cation and anion alternately stacked in almost parallel and superimposed manner to form column and layer structures. The cocrystal of 2A5NP with 3-nitrobenzenesulfonic acid is crystallized into chiral space group P2(1)2(1)2(1). The 2A5NPH(+) cation and anion are also alternately stacked with some dihedral angle to form column structures. These organic-organic cocrystals are controlled by the aromatic-aromatic interactions as well as multidirectional ionic and hydrogen bondings between the 2A5NPH(+) cations and Ar-SO3- anions. Second-harmonic generation ( SHG) powers of the crystals measured by second-harmonic generation with evanescent wave ( SHEW) technique were, however, smaller than that of urea. The reasons for small SHG powers are discussed based on the molecular arrangements.
  • Yagi, I, K Ogai, T Kondo, A Fujishima, K Ueda, K Uosaki
    CHEMISTRY LETTERS 32 11 1050 - 1051 2003年11月 [査読有り][通常論文]
     
    The substitution of surface hydrogen on boron (B)-doped diamond electrodes during electrochemical hydrogen evolution was confirmed using TOF-ESD method. The results show that surface-H(D) was substituted by D(H) as a result of the reduction of D+(H+) in solution during the electrochemical hydrogen evolution at the B-doped diamond.
  • Tadashi Awatani, Ichizo Yagi, Hidenori Noguchi, Kohei Uosaki
    Journal of Electroanalytical Chemistry 524-525 1 184 - 193 2002年05月03日 [査読有り][通常論文]
     
    Electrochemical deposition (electrodeposition) and dissolution processes of Pd on a polycrystalline Au electrode surface in HClO4 solution containing PdCl42- were investigated by second harmonic generation (SHG) measurements. Both 1064 nm (near-IR) and 600 nm (visible) excitations were employed to monitor the SHG behavior in situ. Under the near-IR excitation, the resulting SHG signal contained contributions from both the Pd deposit and the adsorbed PdCl42-. On the other hand, the adsorption of the PdCl42- did not affect the SHG signal under the visible excitation. The SHG signal under the visible excitation was resonantly enhanced with the first and second monolayer depositions of Pd but declined with higher Pd coverage. These results confirm the unique structure and property of an ultra-thin Pd overlayer on gold, suggested by scanning tunneling microscopy (STM), surface X-ray scattering (SXS) and electrochemical measurements at electrodeposited Pd thin layers on single crystalline gold surfaces. © 2002 Elsevier Science B.V. All rights reserved.
  • Yagi, I, K Tsunozaki, A Fujishima, B Ohtani, K Uosaki
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 149 1 E1 - E5 2002年01月 [査読有り][通常論文]
     
    The influences of nitrogen addition and the attenuation of microwave power during microwave plasma-assisted chemical vapor deposition (MPCVD) of diamond films on electrochemical properties of the grown films were investigated. Although diamond films grown in the presence of a small amount of nitrogen did not contain sp(2) carbon and appeared to be normally deposited films, the electrical and electrochemical properties were different from films grown under an atmosphere without nitrogen. Especially, the potential windows of diamond films grown in the presence of nitrogen at low microwave power were very wide and extended to 3.6 V in sulfuric acid solution, which is comparable to the widest value of the potential window of diamond electrodes reported till now. It was also found that the attenuation of the plasma power during MPCVD by itself was effective in the expansion of the potential window because of the defect-free growth of diamond crystals. (C) 2001 The Electrochemical Society.
  • H Koshima, M Hamada, Yagi, I, K Uosaki
    CRYSTAL GROWTH & DESIGN 1 6 467 - 471 2001年11月 [査読有り][通常論文]
     
    A series of noncentrosymmetric cocrystals were prepared from 2-amino-5-nitropyridine (2A5NP) and achiral benzenesulfonic acids (Ar-SO3H), which were designed for nonlinear optical materials. The cocrystals are colorless, and the melting points are fairly high, at around 200degreesC. Both components are commonly crystallized in 1:1 ionic forms of 2A5NP(+).Ar-SO3-. The crystal of 2A5NP and 3-methyl-4-nitrobenzenesulfonic acid belongs to chiral space group P2(1)2(1)2(1), in which the 2A5NP(+) cation and the anion are alternately stacked with a dihedral angle due to the large sulfonic anion to form column structures. Crystals of 2A5NP with both p-toluenesulfonic acid and p-chlorobenzenesulfonic acid are crystallized into noncentrosymmetric space group Pc and are isomorphic with each other. The 2A5NP+ cation and anion in each crystal are also alternatively stacked to form independently elongated zigzag and layer arrays in perpendicular directions. The crystal of 2A5NP and p-phenolsulfonic acid belongs to acentric space group Pna2(1), in which herringbone networks of 2A5NP(+) cations are arranged in the lattice. The feature of these organic-organic crystals is that the molecular packings are controlled by the aromatic-aromatic interactions as well as multidirectional hydrogen bondings between the 2A5NP(+) cations and anions. Second-harmonic generation (SHG) powers measured by the SHEW (second-harmonic generation with evanescent wave) technique revealed the high SHG efficiencies of cocrystals of 2A5NP with p-toluenesulfonic and p-phenolsulfonic acid, comparable to those of the well-known m-nitroaniline and 4-(dimethylamino)-3-acetamidonitrobenzene (DAN), respectively.
  • H Masuda, T Yanagishita, K Yasui, K Nishio, Yagi, I, TN Rao, A Fujishima
    ADVANCED MATERIALS 13 4 247 - + 2001年02月 [査読有り][通常論文]
     
    Alumina templates are used to assist the deposition of highly ordered polycrystalline diamond nanocylinders (see Figure) and diamond-like carbon nanotubes. The growth of diamond is carried out by microwave plasma-assisted CVD, using acetone as the carbon source. The dimensions of the nanofibers are easily controllable and this technique could be adopted to prepare arrays for various applications.
  • H Notsu, Yagi, I, T Tatsuma, DA Tryk, A Fujishima
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 492 1 31 - 37 2000年09月 [査読有り][通常論文]
     
    Oxygen-containing functional groups can be introduced onto the surface of polycrystalline boron-doped diamond electrodes by either anodic polarization or oxygen plasma treatment. Of these, the carbonyl groups are of particular interest and can be studied specifically by means of specific chemical modification with dinitrophenylhydrazine (DNPH). The modification of the surface carbonyl groups with DNPH retards the Fe2+/3+ redox reaction, which is known to be catalyzed by carbonyl groups. Anodic polarization generated a larger number of carbonyl groups per unit area that were reactive with DNPH than that generated by oxygen plasma treatment. The molar ratio of the DNPH-reactive carbonyl groups to the total of all types of oxygen atoms could be as high as 5% for electrochemically oxidized diamond surfaces. This value is reasonable in view of steric limitations. The total number of carbonyl groups per unit area introduced by oxygen plasma treatment was probably larger than that introduced by anodic polarization, but the number that can react with DNPH is lower due to disordering by energetic oxygen ions. (C) 2000 Elsevier Science B.V. All rights reserved.
  • M Yanagisawa, H Tai, Yagi, I, DA Tryk, A Fujishima, L Jiang
    DIAMOND MATERIALS VI 99 32 423 - 427 2000年 [査読有り][通常論文]
     
    Both homoepitaxial and polished polycrystalline diamond films were used to produce micrometer and sub-micrometer-scale patterns that were characterized by differences in conductivity, topography, and friction force. In some cases, the differences in conductivity were more than two orders of magnitude. The patterns were produced by repetitively scanning the surface with a gold-coated AFM tip, with the sample biased positive (+2 to +3 V) vs, the tip. It may be possible to use the patterns thus produced for the preparation of nanoscale electronic devices such as field-effect transistors.
  • H Notsu, Yagi, I, T Tatsuma, DA Tryk, A Fujishima
    ELECTROCHEMICAL AND SOLID STATE LETTERS 2 10 522 - 524 1999年10月 [査読有り][通常論文]
     
    Two simple methods for chemically modifying boron-doped diamond (BDD) films by oxidative treatment were examined. These treatments have shown promise in imparting selectivity to BDD electrodes, for example, between dopamine and ascorbic acid (AA). BDD surfaces were treated either by oxygen plasma or anodic polarization in alkaline solution. The treatments resulted in the incorporation of substantial amounts of oxygen on the surface and also increased the overpotential for AA oxidation. Interestingly, using cathodic polarization, the increase in overpotential was largely negated for the anodically treated surface, whereas it was little affected on the plasma-treated surface. Two different models are proposed to explain this difference in behavior. (C) 1999 The Electrochemical Society. S1099-0062(99)05-079-6. All rights reserved.
  • Yagi, I, K Tsunozaki, DA Tryk, A Fujishima
    ELECTROCHEMICAL AND SOLID STATE LETTERS 2 9 457 - 460 1999年09月 [査読有り][通常論文]
     
    The photoelectrochemical response of boron-doped diamond electrode/electrolyte interfaces was examined to establish the influence of the chemical termination at the diamond surface on the dynamics of photogenerated carriers. Photocurrent transients resulting from pulsed excimer laser irradiation at hydrogen-terminated (as-deposited) diamond electrodes and at oxygen-terminated electrodes, which were prepared either by exposing the surface to oxygen plasma or by anodic polarization in an electrolyte solution, were compared. A significant difference between the photocarrier dynamics for these two surfaces was observed in terms of the full width at half-maximum of the photocurrent transients. The much faster decay rate that was observed for the oxygen-terminated surface is attributed to either the depassivation of deep trapping sites due to removal of subsurface hydrogen or to the introduction of defect recombination sites by the oxygen plasma. (C) 1999 The Electrochemical Society. S1099-0062(99)03-024-2. All rights reserved.
  • A Fujishima, TN Rao, E Popa, BV Sarada, Yagi, I, DA Tryk
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 473 1-2 179 - 185 1999年09月 [査読有り][通常論文]
     
    Highly boron-doped diamond thin-film electrodes were examined for various possible applications in electroanalysis. Electrochemical oxidation of dopamine and NADH was investigated using cyclic voltammetry and chronoamperometry. Comparison experiments were performed using glassy carbon electrodes. Anodically treated diamond electrodes made it possible to determine dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in acidic media. A detection limit of 50 nM was obtained using chronoamperometry. The treated electrodes were found to be stable for several months. Electrochemical oxidation of NADH was carried out at as-deposited diamond electrodes, with which very stable and reproducible cyclic voltammograms for NADH oxidation were obtained, unlike glassy carbon, at which a significant positive shift (similar to 200 mV) in the peak potential was observed within 1 h. The amperometric detection limit was found to be similar to 10 nM. Interference of ascorbic acid was minimal using untreated electrodes when the concentration of ascorbic acid was comparable to the NADH concentration. Diamond microelectrodes small enough to consist of only one or two high quality microcrystals were fabricated in order to compare the electrochemical behavior with that of polycrystalline thin film electrodes, which contain large numbers of grain boundaries, at which non-diamond (sp(2)) carbon can exist. This work demonstrates the potential of diamond electrodes for electroanalytical applications. (C) 1999 Elsevier Science S.A. All rights reserved.
  • Yagi, I, H Notsu, T Kondo, DA Tryk, A Fujishima
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 473 1-2 173 - 178 1999年09月 [査読有り][通常論文]
     
    Oxygen-terminated diamond electrodes were prepared by exposing as-grown hydrogen-terminated diamond thin films to oxygen plasma. The as-grown surfaces, which were highly hydrophobic, become hydrophilic after the oxygen plasma treatment. The apparent surface conductivity was not significantly changed after the oxygen plasma treatment. However, the electrochemical responses to several redox systems became remarkably different. For example, the cyclic voltammetric anodic-cathodic peak separations for the oxygen-terminated diamond electrodes became extremely large compared to those for the as-grown electrodes. This behavior was examined in comparison with as-grown diamond and glassy carbon electrodes. (C) 1999 Elsevier Science S.A. All rights reserved.
  • TN Rao, Yagi, I, T Miwa, DA Tryk, A Fujishima
    ANALYTICAL CHEMISTRY 71 13 2506 - 2511 1999年07月 [査読有り][通常論文]
     
    Conductive boron-doped chemical vapor-deposited diamond thin films, already known to have superior properties for general electroanalysis, including low background current and a wide potential window, are here shown to have additional advantages with respect to electrochemical oxidation of nicotinamide adenine dinucleotide (NADH), including high resistance to deactivation and insensitivity to dissolved oxygen, Cyclic voltammetry, amperometry, and the rotating disk electrode technique were used to study the reaction in neutral pH solution. Highly reproducible cyclic voltammograms for NADH oxidation were obtained at as-deposited diamond electrodes. The response was stable over several months of storage in ambient air, in contrast to glassy carbon electrodes, which deactivated within 1 h, The diamond electrode exhibited very high sensitivity for NADH, with an amperometric detection limit of 10 nM (S/N = 7), The response remained stable, even in the very low concentration range, for several months. In addition, interference effects due to ascorbic acid were minimal when the concentrations of NADH and ascorbic acid were comparable. An NADH-mediated dehydrogenese-based ethanol biosensor incorporating an unmodified diamond electrode is demonstrated. The present results indicate that diamond is a useful electrode material for the analytical detection of NADH, making it attractive for use in sensors based on enzyme-catalyzed reactions involving NADH as a cofactor.
  • 八木一三, 藤嶋昭
    表面技術 50 6 486 - 493 一般社団法人 表面技術協会 1999年06月01日 [査読無し][招待有り]
  • 梶村綾子, 須磨岡淳, 児玉照幸, 八木一三, 藤嶋昭, 小宮山真
    希土類 34 178 - 179 1999年05月27日 [査読無し][通常論文]
  • T Kondo, S Horiuchi, Yagi, I, S Ye, K Uosaki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 121 2 391 - 398 1999年01月 [査読有り][通常論文]
     
    The second harmonic (SH) intensity at gold electrodes modified with self-assembled monolayers (SAMs) of two novel molecules, which have trans-ferrocenyl-nitrophenyl ethylene and thiol groups as the second harmonic generation and surface-attached groups, respectively, was found to be strongly dependent on the oxidation state of the ferrocene group. The SH intensity increased when the ferrocene moiety of the SAMs was oxidized electrochemically to the ferricenium cation, and it decreased and returned to the original value when the ferricenium cation of the ferrocene moiety was reduced to neutral ferrocene. These changes were reversible and were repeated many times. The molecular orientation change in each SAM upon reduction/oxidation of the ferrocene moiety was investigated by in situ Fourier transform infrared reflection-absorption spectroscopy, and the hyperpolarizabilities of these molecules were calculated using a computational electronic structure model. The origin of the SH intensity change is discussed on the basis of these results.
  • Yagi, I, S Nakabayashi, K Uosaki
    SURFACE SCIENCE 406 1-3 1 - 8 1998年05月 [査読有り][通常論文]
     
    Electrochemical deposition of Te on a single crystal Au(lll) electrode was monitored by the optical second harmonic generation (SHG) technique. The rotational anisotropic SHG measurement was used to estimate the overall symmetry of the electrode surface during the first underpotential deposition (upd), the second upd and bulk deposition of Te in real time. The formation of the first Te upd layer seemed to proceed in two steps as the SH rotational anisotropy became rather isotropic in the middle of the first upd and, then, the anisotropic character of the surface recovered again after the completion of the first upd. The experimental results suggest random deposition in the initial stage followed by the island growth, leading to the highly ordered (root 3 x root 3)R30 degrees structure. It was also found that the anisotropic character of the overall surface symmetry was attenuated after the second upd and bulk deposition of Te. (C) 1998 Elsevier Science B.V. All rights reserved.
  • I Yagi, S Nakabayashi, K Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY B 102 15 2677 - 2683 1998年04月 [査読有り][通常論文]
     
    The electrodeposition of Te on a single-crystalline Au(111) electrode was studied with 1064-nm-excited SH rotational anisotropy measurements. The SH rotational anisotropy was significantly changed with the first underpotential deposition (upd) of Te, and the bulk Te deposition attenuated the anisotropic character of the overall surface symmetry. The change in the SH rotational anisotropy during the first upd of Te was examined using two different models. The first model considered only the contribution of the Au(111) surface to the SHG response, while the second one took into account the contributions of both the Au(111) substrate and the adsorbed Te layer. In the former case, the change in the SH rotational anisotropy can be explained by considering the quenching of the nonlinear susceptibility of the Au(111) surface. The analysis based on the latter model resulted in a rotation angle of 608 for the adsorbed Te layer against the the Au(111) lattice. This value was not consistent with that expected from the adsorbate structure of the first upd layer of Te, i.e., (root 3x root 3)R30 degrees. Thus. the former model seems to be more appropriate to explain the present results. The SH rotational anisotropy measurement also suggests that the morphology became more isotropic after the bulk Te deposition.
  • S Nakabayashi, Yagi, I, N Sugiyama, K Tamura, K Uosaki
    SURFACE SCIENCE 386 1-3 82 - 88 1997年10月 [査読有り][通常論文]
     
    When a platinum electrode is dipped into aqueous sulfuric acid solution containing formaldehyde, the surface is covered by CO, which is formed by the dissociative adsorption of formaldehyde. A second harmonic generation voltammogram pumped by a 532 nm laser pulse and photo-reflectance voltammogram probed by a 670 nm laser beam are sensitive to the surface CO and surface oxide, respectively. The experiments demonstrate that the anodic oxidation pathway of the formaldehyde through CO adsorption proceeds by coupling with the surface oxide formation and that the CO controls the dual reaction pathway, the anodic and cathodic path of the reaction, and induces a non-linear self-sustained oscillation. The kinetics of the dissociative adsorption is discussed based on the time course of the current induced by the laser desorption of CO. (C) 1997 Elsevier Science B.V.
  • Yagi Ichizo, Nakabayashi Seiichiro, Uosaki Kohei
    Journal of Physical Chemistry B 101 38 7414 - 7421 American Chemical Society 1997年09月18日 [査読有り][通常論文]
     
    The interfacial electronic structure of a CO-covered polycrystalline platinum electrode has been studied by using the optical second harmonic generation (SHG) and sum frequency generation (SFG) techniques with various excitation wavelengths. Although the nonlinear optical (NLO) signal was enhanced by the absorption of CO at all excitation wavelengths employed in this study, the potential dependent behaviors of the NLO signal were different between the near-infrared excitation and the visible excitation. The difference was attributed to the different mechanisms for the enhancement of the NLO signal. While the electron transition from the Fermi level of Pt to the unoccupied 2πa* orbital of adsorbed CO was considered to be coupled with the NLO photon in the case of visible excitation, the dc field induced SHG regime was applied to the result obtained by the near-infrared excitation.
  • K Uosaki, M Koinuma, T Kondo, S Ye, Yagi, I, H Noguchi, K Tamura, K Takeshita, T Matsushita
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 429 1-2 13 - 17 1997年05月 [査読有り][通常論文]
     
    The grazing incidence X-ray diffraction technique has been applied to monitor the anodic dissolution process of GaAs(001) in 0.1M HCl solution. The surface diffraction intensity for the [11] direction of GaAs(001) was clearly observed and it decreased with time when the positive potential was applied to the electrode. (C) 1997 Elsevier Science S.A.
  • Ichizo Yagi, Juliette M. Lantz, Seiichiro Nakabayashi, Robert M. Corn, Kohei Uosaki
    Journal of Electroanalytical Chemistry 401 1-2 95 - 101 1996年01月24日 [査読有り][通常論文]
     
    The electrodeposition of tellurium (Te) on polycrystalline gold electrodes was studied using in situ optical second harmonic generation (SHG) at two different excitation wavelengths. On excitation at 1064 nm, the SH signal decreased dramatically with the first Te underpotential deposition (upd) and increased slightly with the second upd and the bulk deposition of Te. There was a linear correlation between the square root of the SH intensity from the surface and the surface coverage of Te, although the proportionality constant of this correlation for the first Te upd was different from those for the second upd and bulk deposition. This is possibly because of the stronger interaction of the first upd layer of Te than the second and bulk layer of Te with the substrate surface. However, on excitation at 585 nm, the behavior of the SH signal was more complicated, especially during the desorption process of the first Te monolayer. An increase in the SH intensity was observed with the first Te upd, but this increase in SHG still continued in the potential region in which no deposition of Te occurred. These results are interpreted by considering the existence of an optical resonance at the Au surface covered with a Te monolayer.
  • Yagi, I, S Nakabayashi, K Uosaki
    CHEMISTRY LETTERS 7 529 - 530 1996年 [査読有り][通常論文]
     
    In situ optical second harmonic generation(SHG) technique was employed to investigate the electrochemical oxidation of formaldehyde on a polycrystalline Pt electrode. At 532 nm excitation, the SH signal generated at a Pt surface seems to be enhanced by the existence of adsorbed CO and can be related to the surface coverage of CO(a) which cannot be determined by the electrochemical methods. Thus, the potential dependence of the SH signal provides useful information to understand the mechanism of this reaction.
  • K SHIMAZU, YAGI, I, Y SATO, K UOSAKI
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 372 1-2 117 - 124 1994年07月 [査読有り][通常論文]
     
    Mass transport accompanying the redox process of ferrocenyle-undecanethiol monolayers has been examined by an electrochemical quartz crystal microbalance (EQCM) for both compact and loosely packed layers with different surface coverages prepared by self-assembly method. Ferricinium cations formed upon the oxidation of ferrocene group associate with anions in solution to form ion pairs. The anion association was not accompanied by water incorporation into the layers independent of the surface coverage, unless the layers were pretreated with water before the measurements were made. Immersion of the thiol-modified electrode in water caused a drastic increase in interfacial mass transport upon oxidation, particularly at a loosely packed layer. It is concluded that this increase is the result of the incorporation of water molecules into the space between the alkyl chains of the oriented ferrocenylundecanethiol. The space seems to be pre-occupied by hexane during the self-assembly process.
  • K SHIMAZU, Y SATO, YAGI, I, K UOSAKI
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 67 3 863 - 865 1994年03月 [査読有り][通常論文]
     
    Self-assembled monolayers of 11-ferrocenyl-1-undecanethiol on Pt have been characterized with an electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy. Well-packed monolayers were defect-free, but less compact than on Au. The high affinity of Pt for oxygen made the monolayer relatively unstable compared with monolayers on Au.
  • K SHIMAZU, YAGI, I, Y SATO, K UOSAKI
    LANGMUIR 8 5 1385 - 1387 1992年05月 [査読有り][通常論文]
     
    The self-assembling process of ferrocenylundecanethiol on a gold surface has been measured in situ using the electrochemical quartz crystal microbalance (EQCM). Initial adsorption was fast and was followed by the slow adsorption whose rate was 2 orders of magnitude smaller. The number of adsorbed thiol molecules, estimated from the frequency change, suggests the formation of the monomolecular layer of the thiol. This number agrees well with that calculated from the electrochemical charge associated with oxidation/reduction of the monolayer in 1 M HClO4. The EQCM was also used to follow the mass change during the oxidation/reduction of the ferrocenylundecanethiol monolayer. It was confirmed that anions are incorporated into the self-assembled layer upon oxidation of the ferrocene group.

書籍

  • 犬飼 潤治, 米田 雅一, 唯 美津木, 石黒 志, 松井 公佑, 折笠 有基, 内本 喜晴, 上野 武夫, 矢口 紀恵, 清水 貴弘, 山田 裕久, 井上 元, 八木 一三, 徳増 崇, 棟方 稔久, 北原 辰巳, 杵淵 郁也, 宇高 義郎, 大徳 忠史, 是澤 亮, 西田 耕介, 村川 英樹, 杉本 勝美, 浅野 等, 竹中 信幸, 津島 将司, 平井 秀一郎, 墻内 孝祐, 原 正則, 東海林 篤, 近久 武美, 小川 邦康, 横内 康夫, 上野 明 (担当:共著)
    S&T出版株式会社 2015年08月 (ISBN: 4907002475) 247

講演・口頭発表等

作品等

  • CO2電解還元電極の最適化と反応機構の研究
    2001年
  • 電気化学界面における水素の観察と定量
    2001年
  • Direct Observation of Adsorbed Hydrogen
    2001年

その他活動・業績

特許

共同研究・競争的資金等の研究課題

  • 生体模倣電極触媒への展開を指向した金属酵素修飾電極におけるオペランド振動分光計測
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 八木 一三
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 八木 一三
     
    本研究ではテラヘルツラマン分光法と表面増強ラマン散乱(SERS)を組み合わせ、燃料電池カソードで起こる酸素還元反応(ORR)や蛋白質・酵素など生体高分子を電極に固定した状態で駆動される電極触媒反応などに応用することを目的としている。光源や超狭帯域ノッチフィルタなどを検討し、He-Neレーザー光源に市販のブラッググレートノッチフィルタ(BNF)を組み合わせた光学系を従来のラマン顕微鏡に組込み、テラヘルツラマン顕微鏡を構築した。電極反応において変化が予想されるナノ構造体のフォノン計測が可能かどうか見極めるため、金クラスタを計測した結果、明確なバンドを観測した。
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2012年 -2014年 
    代表者 : 八木 一三
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2009年 -2010年 
    代表者 : 八木 一三
     
    電気化学環境下、特に腐食が起こりやすい酸性で貴電位印加状態、において安定な分光信号増強能を有する分光電気化学基板の製作を検討し,プラズモニック結晶基板のデザインとその評価を試みた。具体的には燃料電池電極触媒表面における反応の原子・分子レベルでの解析を目指している。当初、逆ピラミッドピット型プラズモニック結晶により、表面増強ラマン散乱(SERS)活性な基板を製作し、単分子層レベルの感度を有することを示すことができたが、白金を用いたSERS活性基板の構築には至っていない。そこで、表面プラズモンポラリトン(SPP)の伝搬長が白金では非常に短いことを考慮し、金表面のSPPを白金に集約し、白金表面での増強を実現することを検討した。そのためにポリスチレン(PS)球を鋳型とする球状セグメントボイド(SSV)型のプラズモニック結晶を製作することにした。ラピッドコンベクションデポジション法により、金平面基板表面に直径600nmのPS球単粒子層を構築し、その隙間を金メッキにより埋めることで種々の深さを有するAu-SSV基板を製作した。引き続きPS球を保持したまま、Pt電析を行うことでAuボイドの上部にPtリムを構築した。Ptリムの有無やプローブ分子の導入法を変えながらラマン信号計測を行うことで、Auボイド内のSPPをPtリムに集約できることを明らかにした。一方、プラズモニック結晶構造の裏面から赤...
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2008年 -2008年 
    代表者 : 八木 一三
     
    本研究では、数十年に亘って未解明なままである燃料電池電極表面で起こる反応機構を明らかにするため、表面に生じる反応中間体の濃度を高速で追跡することが可能な分光計測ツールを開発することを目的としている。そのため、高感度・高速で、かつ表面構造が規定された反応場で利用できる必要がある。今年度は、分子検出に用いる分光信号を増強するために、試料電極表面にマイクロメートルスケールの凹みを形成することで高感度化が可能であることを実証した。
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2005年 -2006年 
    代表者 : 八木 一三, 野口 秀典
     
    本年度は主として、均一系であるRu三核錯体およびプルシアンブルーナノ粒子の光励起振動ダイナミクスの計測と光励起時間分解和周波発生分光系の構築に注力した。Ru三核錯体の光励起振動ダイナミクス計測については、これまでよりもより高い時間分解測定を行ったところ、従来観測されていた配位COのホットバンド(本来の吸収バンドと比較して若干低波数側に観測されていた)は、最初から低波数側に現れるのではなく、まずバンドの広がりが認められ、数百フェムト秒以内に波数シフトを示していることがわかった。これは、以前報告されている、Ru単結晶表面に吸着したCO分子の光パルス照射後のフォノン変換現象と酷似しており、おそらく三核といえどもRu30格子内でフォノンの生成が起こっているためと考えられる。また、プルシアンブルー(PB)ナノ粒子については、PBの電荷移動バンドを励起した際に、生成する緩和した双安定状態と目される、近赤外領域の吸収と、中赤外領域の吸収バンドが明確に観測された。この吸収バンドの時間分解応答は、以前報告されている、水溶性のPBコロイドと比較して遙かに長寿命であり、ナノサイズ化の影響が明確に観測されたと考えられる。一方、時間分解光励起和周波発生(SFG)分光システムの構築については、現在、ようやく可視-赤外SFG測定が可能になった段階であり、新たにポンプ光のラインを増設することができたが、ポン...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2005年 -2006年 
    代表者 : 八木 一三
     
    本年度は、種々のポリマーを鋳型とする白金または金ナノ粒子を電極表面に固定するための最適な組み合わせを明らかにすることに注力した。具体的には、ポリアクリル酸(PAA)のようなポリアニオンを鋳型として調製した白金ナノ粒子、ポリエチレンイミン(PEI)のようなポリカチオンを鋳型として調製した白金ナノ粒子、ならびにポリビニルピロリドン(PVP)に代表される中性のポリマーを鋳型とする白金ナノ粒子および金ナノ粒子を、対応するポリマーとの交互積層を行った。白金ナノ粒子を交互積層した場合には、電気化学測定により、積層数に対する水素吸脱着波の変化から、担持できた白金量を見積もるとともに、酸素還元活性を評価した。一方、金ナノ粒子の場合には、透明基板を用いて、吸光度変化から積層量を評価した。いずれの場合も、10層目あたりから、積層回数と実際の積層量との相関が線形からずれ、表面が次第にラフネスを増大させていくことがわかった。ただし、その度合いには対ポリマーの分子量や構造、親・疎水性にかなり影響を受けることもわかった。また、基板の種類に応じて、前処理を行うことが、安定した積層を行う上で、有用であることもわかってきた。以上の結果については、より系統的な研究の必要性がある。一方、さらに実際の電極触媒研究と関連づけるために、白金ナノ粒子を担持した触媒粒子の表面をポリマーで処理し、その表面電荷を利用して、サブ...
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2002年 -2002年 
    代表者 : 八木 一三, 魚崎 浩平
     
    本研究では、波長可変(紫外・可視:300〜790nm、赤外:2.4〜11μm)超短パルス(〜100fs)レーザーと電気化学測定を組み合わせた超高速分光システムを用い、Si、TiO_2、GaAsなどの半導体電極の光電子移動ダイナミクスを追跡した。本年度の研究成果は以下の通りである。1.可視光ポンプ-中赤外(吸収)プローブ画定によるCdS_XSe_<1-X>超微粒子ドープガラスにおける光生成キャリヤーダイナミクス:本年度は4種類のCdS_XSe_<1-X>超微粒子ドープガラスについてキャリヤーダイナミクス測定を行った。サブピコ秒で減衰する速い成分とそれに続くピコ秒で減衰する遅い成分が観測されている。これまでの研究によって各成分は帰属されており、速い成分は正孔トラッピング、遅い成分は電子トラッピングに対応する。これらの結果から、ガラスマトリクス中における超微粒子の光励起キャリヤーダイナミクスが観測可能であることが示された。2.表面和周波発生法を用いたTiO_2表面における吸着分子の振動分光:表面反応の詳細を理解するためには実際に反応が起こる条件で対象を観察することが重要であり、真空を必要としないSFG分光測定はこの目的に最適な手法である。本研究では二酸化チタン上におけるアルコール分子の吸着構造の評価を行った。試料にはTiO_2微粒子の希釈水溶液をスピンコートして作製した膜とゾル-ゲ...
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 2000年 -2000年 
    代表者 : 八木 一三, 武田 定, 魚崎 浩平
     
    硼素をドープした導電性ダイヤモンド電極は、きわめて広い電位窓と微小な残余電流を有し、しかも酸化還元種に対する応答が良いという特異的に優れた電極材である。ダイヤモンド表面の終端水素や表面近傍に存在する原子状水素の存在が表面の伝導性や電子放出能に大きく影響することが示唆されているが、ダイヤモンド内に局在する水素原子がどのような電子状態を形成しているか、あるいはどのような機構でダイヤモンド表面特性を変えるのか、という点については、完全な理解には至っていない。本研究では、ダイヤモンド薄膜表面及び表面近傍層における原子状水素の濃度を直接決定すると同時に、薄膜の電気化学特性・光電気化学特性との相関を細部まで調べ、水素が及ぼす影響を定量的に評価した。ダイヤモンド電極表面の原子状水素濃度を測定する手法としては、電子線励起脱離(ESD)と飛行時間型質量分析装置(TOF-MASS)を利用した走査型水素顕微鏡により表面層に局在する水素原子を検出・画像化した。測定はプラズマアシストCVD成長後のAs-Grown試料、アノード酸化処理を行った試料、および重水素化した硫酸の重水溶液中で重水素発生を行った試料について行った。各試料のESD-TOF-Massスペクトルから、As-Grown表面と比較すると、電解処理表面(重水素発生・アノード酸化処理の双方)で明らかに酸素の存在量の増大ならびに酸素の状態の変化...
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1999年 -2000年 
    代表者 : 八木 一三
     
    本研究では、ボロンドープダイヤモンド電極の陽極酸化などによるドーパミン/アスコルビン酸系への電気化学的選択性発現機構等を電気化学的・光電気化学的なアプローチにより明らかにすることを目的としている。ダイヤモンド電極における電気化学的選択性の発現においては、表面水素終端を置き換えて生成される酸素終端が非常に重要な役割を担っていることが、XPS、電気化学測定などにより明らかになった。特に、酸素終端化処理法により、その影響が異なってくることもわかってきた。酸素プラズマ処理は、その中でも最も表面への影響が大きく、陽極酸化処理よりも顕著な電気化学的選択性、すなわち特定の酸化還元種に対する電子移動速度の低下が観測された。さらに表面カルボニル基と選択的に反応するDNPH分子により修飾を行ったところ、電子移動速度が劇的に変化したことから、カルボニル基の存在が大きく効いていることがわかった。また、光電気化学ダイナミクスの測定においても、酸素プラズマ処理により、光電流の減衰が早くなり、長波長域でも光電流が観測されることがわかった。この事実は、酸素プラズマ処理によりダイヤモンド表面が酸素終端化されるのみならず、欠陥の生成や、準表面領域における水素放出が引き起こされていることを示唆している。したがって表面および表面近傍に存在する水素の影響を定量的に評価する必要がある。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 1998年 -2000年 
    代表者 : 藤嶋 昭, 八木 一三
     
    近年の社会情勢において地球温暖化などの環境間題は深刻であり、排気される炭酸ガスなどの再利用の必要性は緊急に解決するべき間題である。我々は炭酸ガスを電気化学的手法で還元・再資源化し、資源的に有用性の高いエチレンやアルコールを得るシステムの開発、およぴその応用範囲の拡大を最終日的として、特にダイヤモンド電極を利用した光電気化学法に着目し、研究を遂行してきた。ダイヤモンドはこれまでに、高硬度性を利用した切削工具、また高熱伝導性を利用したヒートシンクとして応用がなされてきた。そして現在、半導体性と高熱伝導性を利用した次世代の電子デバイスとしての研究がなされている。これに対して、半導体性と化学的安定性を利用した電極への応用に関した本研究は、きわめて独創的である。化学的安定性のおかげで、どんな過酷な条件下でも電極自身の劣化を考慮する必要性がない。さらに数日問の連続運転を行っても極めて安定であった。よって環境間題に対しての負荷が少なく、メンテナンスの必要の少ない系が構築できた。研究の成果を列挙すると以下のようになる。1)マイクロ波プラズマCVD装置によるフリースタンディングp型半導体ダイヤモンド薄膜の作製とその物性評価2)フリースタンディングダイヤモンド薄膜のXe-Hgランプ照射下における光電気化学的特性の評価、および、シリコン基板付きのダイヤモンド薄膜電極の光電気化学的特性との比較検討3...
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 1999年 -1999年 
    代表者 : 八木 一三
     
    本研究においては、導電性単結晶薄膜の成長を試み、単結晶を用いてダイヤモンド電極が本来共有する電気化学及び光電気化学特性の評価を目的としている。ここでは、人工合成ダイヤモンド単結晶基板上に導電性ダイヤモンド薄膜を作製するホモエピタキシャル成長の結果について報告する。ダイヤモンド薄膜の成長はマイクロ波プラズマCVD法により行った。基板にオフ角度をつけることにより基板上のステップ幅が基板表面に入射した炭素前駆体の拡散長より短くなり、ステップフロー成長が起こりやすくなった。結果として成長膜は平坦な単結晶(100)面であることがわかった。得られた薄膜は結晶粒界、sp^2炭素が少なく、(100)面が揃っているので、従来の多結晶薄膜に比べてより詳細にダイヤモンド電極の電気化学特性が評価できる。硝酸溶液中におけるサイクリックボルタモグラムでは、水素発生・酵素発生電流の立ち上がりがそれぞれカソード・アノード方向にシフトした。単結晶表面の抵抗率が多結晶のそれよりも高いことから、ボロンドープ量が低く、irドロップのために水素・酵素過電圧が大きいものと考えた。実際、ボロン導入が起こりやすい(111)電極では電位窓が多結晶電極とほぼ同程度のCVが報告されている。しかしながら、電解質溶液中にヘキサシアノ鉄錯体やヘキサアンミンルテニウム錯体などの一電子酸化還元種を導入した場合、多結晶電極と殆ど変わらない準...
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 1999年 -1999年 
    代表者 : 八木 一三, 藤嶋 昭
     
    B/C/N化合物の作製には、プラズマ化学気相成長(PCVD)装置を使用した。合成温度を比較的抑えることで、グラッシーカーボン様構造を得ることができると予想された。B/C/N化合物を合成する基板としては、Si基板を主として用いた。作製したBCN化合物の評価は、構造評価ならびに組成分析を併用した。作製時に各各の元素の組成比を変え、作製した薄膜の組成比と比較し、次回の反応条件にフィードバックした。導電性評価は、4探針プローブを用いて測定し、電気化学特性は、主として電位窓の大きさ、酸化還元種に対するレスポンスをサイクリックボルタンメトリー法により評価した。成膜条件を最適化するために、多くのパラメータを変えて成膜を行ったが、ステージ高さと溶媒タンクバブリング用のガス流量・組成が最も影響が高かった。液相ボロン濃度20000ppmで作製した膜ではアモルファスsp^3が増大しており、ボロン導入量が増大した。得られたB,N-ドープダイヤモンド電極のNa_2SO_4電解質溶液中で得られたサイクリックボルタモグラム(CV)では、どちらも4Vに達する非常に広い電位窓を示した。ボロンのみをドープしたダイヤモンド電極については、これまでに報告されている最大の値でも3.5V程度であり、ダイヤモンド結晶のクオリティが低いほどその電位窓が狭くなるという認識が一般化している。この事実を加味すれば、B,N-同時ド...
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 1998年 -1998年 
    代表者 : 八木 一三
     
    近年ダイヤモンドは、その化学的安定性やホウ素のドーピングによる導電性から電気化学においてHOPGやグラッシーカーボンなどのsp^2炭素材料に次ぐ新規の炭素電極材料として注目され始めてきた。これまでの研究では多結晶薄膜が用いられ、sp^2炭素、結晶粒界等の存在、面が揃っていない、等の多結晶膜の特徴がどのように電気化学特性に影響しているのか明らかにされてこなかった。ダイヤモンド電極の真の電気化学特性を明らかにするためには、白金などの貴金属電極の場合と同様、単結晶電極を用い、原子レベルで制御された表面を用いる必要がある。そこで、本研究においては、導電性単結晶薄膜の成長を試み、単結晶を用いてダイヤモンド電極が本来有する電気化学及び光電気化学特性の評価を目的としている。ダイヤモンド薄膜の成長はマイクロ波プラズマCVD法により行った。基板として人工合成単結晶ダイヤモンドの(100)面を用い、成長前に表面を(100)面に対して[110]方向に約4度傾けて再研磨したものを用いた。ヘテロエピタキシャル成長の場合は、火炎溶融法で作製したPt(111)単結晶を基板とした。ダイヤモンド基板上への成長膜は平坦な単結晶(100)面であることがわかった。基板にオフ角度をつけることにより基板上のステップ幅が基板表面に入射した炭素前駆体の拡散長より短くなり、ステップフロー成長が起こりやすくなったと考えられる。...
  • 固液界面における超高速ダイナミクスの追跡
  • 非線形分光法による電極表面反応の追跡
  • ダイヤモンド電極の電気化学特性
  • Ultrafast dynamics at solid/liquid interfaces
  • Monitoring of the Electrochemical Reactions by Nonlinear Optics.
  • Electrochemical Properties of Diamond Electrode

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  • 大学院共通授業科目(教育プログラム):JICA開発大学院連携プログラム環境科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 再生可能エネルギー、賦存量、太陽エネルギー、風力、地熱・温泉熱、バイオマス、水力、水・エネルギー・食料ネクサス、トレードオフ、生態系、温室効果ガス、化石燃料、環境、光合成 Renewable energy, Potential, Solar energy, Wind power, Geothermal and hot spring water heat, Biomass, Hydropower, Water-energy-food nexus, Trade-off, Ecosystem, Greenhouse gas, Fossil fuels, Environment, Photosynthesis
  • 再生可能エネルギー総論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 再生可能エネルギー、賦存量、太陽エネルギー、風力、地熱・温泉熱、バイオマス、水力、水・エネルギー・食料ネクサス、トレードオフ、生態系、温室効果ガス、化石燃料、環境、光合成 Renewable energy, Potential, Solar energy, Wind power, Geothermal and hot spring water heat, Biomass, Hydropower, Water-energy-food nexus, Trade-off, Ecosystem, Greenhouse gas, Fossil fuels, Environment, Photosynthesis
  • ナノ環境材料化学特論Ⅲ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 固体表面構造、ナノ構造材料、自己組織化単分子層、電気化学、半導体電極、電極触媒 Surface structure of solid materials, Nanostructured materials, Self-assembled monolayer, Electrochemistry, Semiconductor electrode, and Electrocatalysis
  • 化学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液

大学運営

委員歴

  • 2021年03月 - 現在   電気化学会   理事
  • 2020年02月 - 現在   日本化学会   速報誌編集委員会委員
  • 2019年03月 - 現在   日本化学会北海道支部   幹事
  • 2013年04月 - 現在   電気化学会北海道支部   幹事
  • 2011年02月 - 現在   電気化学会ナノ界面・表面研究懇談会   常任委員
  • 2009年10月 - 現在   触媒学会燃料電池関連触媒研究会   世話人
  • 2019年01月 - 2021年01月   電気化学会北海道支部   支部長
  • 2015年04月 - 2019年03月   日本分光学会北海道支部   支部長
  • 2017年01月 - 2018年12月   電気化学会北海道支部   副支部長
  • 2014年04月 - 2016年03月   電気化学会北海道支部   常任幹事
  • 2012年02月 - 2014年01月   電気化学会   編集委員会委員


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