Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 72 , Issue 5
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  • Jun YANO, Kenji NOGUCHI, Sumio YAMASAKI, Suzuko YAMAZAKI
    2004 Volume 72 Issue 5 Pages 304-309
    Published: May 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    An aramid resin, poly(p-phenylene terephtalamide) (PPTA) was available on an ITO electrode as a stable matrix film. Electrochromic iridium oxide was electrodeposited on the electrode. In the oxidized state, original iridium oxide without PPTA film showed blue, while the PPTA / iridium oxide film showed greenish blue: the maximum absorption wavelength of the original iridium oxide film was about 650 nm, while that of the PPTA / iridium oxide film was about 600 nm. The XPS-biding energy of Ir 4f5/2 and Ir 4f7/2 electrons was shifted to about 2 eV higher energy, meaning that the color change was probably due to donating of the lone pair electrons of PPTA to the indium. The electrodeposition of Au on the PPTA / iridium oxide film was carried out. The obtained Au-electrodeposited PPTA / iridium oxide film showed quite different electrochromic properties. New redox current peaks appeared in the CV of the film. The film was colored vermilion in the reduced state and greenish blue in the oxidized state. The XPS-biding energy of Ir 4f5/2 and Ir 4f7/2 electrons was shifted to about 2 eV lower energy, implying that the electrodeposition of Au transformed the electronic state and structure of iridium oxide, suggesting the formation of a -Au-CI-Ir- binuclear Cl-bridged complex and/or the plasmon absorption of the Au microparticles dispersed in the PPTA film.

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  • Haruhisa SAITO, Sadao UEGUSA, Takurou N. MURAKAMI, Norimichi KAWASHIMA ...
    2004 Volume 72 Issue 5 Pages 310-316
    Published: May 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Dye-sensitized solar cells were fabricated by using water-based electrolytes for the purpose to realize environmentally benign, green solar cells in which electrolyte solvent, water, can serve as a recyclable medium. Mesoporous TiO2 electrode was treated with ozone and UV light for hydrophilic conversion of the TiO2 mesopore and was dyesensitized with Ru(bipy)2 (SCN)2 in the presence of 4-tert-butylpyridine. These processes for surface activation highly improved photocurrent density and voltage of the electrode in contact with aqueous electrolytes that contain iodide/iodine as redox agents. Replacement of a portion of water with ethanol in the electrolyte composition further enhanced photovoltaic performance. With aqueous electrolyte containing 35% ethanol, photocell achieved power conversion efficiency of 2.2% under exposure to simulated solar light of 100 mW/cm2.

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  • Yi-tai XU, Noriko YAMADA, Takeshi HAMADA, Takashi AMEMIYA, Kiminori IT ...
    2004 Volume 72 Issue 5 Pages 317-321
    Published: May 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    A composite-type optical waveguide was applied to a gas sensor using a thin film of siloxane polymer which absorbs NO2 gas. The waveguide was prepared by using ion exchange (K+-doped base layer, about 2 μm thick) and sputtering (TiO2 top layer, about 20 nm thick, with slopes on both sides). A highly sensitive interferometer was constructed on the basis of the difference in cutoff thickness for TE and TM modes. Changes in thickness or refractive index taking place in the polymer film coated on to the TiO2 part induce phase shifts (Δϕ) of the propagating lightwave. NO2 gas with concentration less than 1 ppb was detected by measuring changes in Δϕ as a function of time. The response was reversible for low concentration, and irreversible for high concentration. The irreversible changes were attributed to the ion-pair formation in the film.

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Technological Reports
  • Osamu HAMAMOTO, Yumi AKAHORI, Sachiko GOTO, Yumi KATO, Mikita ISHII
    2004 Volume 72 Issue 5 Pages 322-327
    Published: May 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    Carbon dioxide was reduced by the surface modified carbon fiber electrodes impregnated with indium to form formic acid which is expected to be available for the chemiluminescent application. The PAN (polyacrylonitrile) based carbon fiber (800°C pre-heated) was baked with aluminum chloride and water in nitrogen atmosphere oven to introduce oxygen atoms and to increase the degree of crystallization, which results in the improvement in hydrogen overvoltage and some electrochemical reactivities. Indium was electrodeposited to the surface modified carbon fibers for the working electrode. The current efficiency of carbon dioxide conversion to formic acid was close to 100%, and trace of by-products such as folmaldehyde and carbon monooxide were detected under the optimum electrochemical conditions. The cell technologies of flow coulometric detectors and redox flow batteries were applied to the design of the electrolytic cells for carbon dioxide reduction.

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  • Hiroshi FUKUNAGA, Mitsuhiro KISHIMI, Tetsuya OZAKI, Tetsuo SAKAI
    2004 Volume 72 Issue 5 Pages 328-333
    Published: May 05, 2004
    Released: June 08, 2019
    JOURNALS OPEN ACCESS

    New paste-type positive electrodes with Ni- or Co(OH)2-coated Ni(OH)2 for nickel/metal-hydride (Ni/MH) battery were prepared using low-cost punching metal as substrate. Their charge-discharge properties were evaluated using non-sealed battery. Electrodes with Ni- and Co(OH)2-coated Ni(OH)2 showed higher discharge capacity than those with Ni and CoO as conductive agents, respectively. SEM observation and resistance of these Ni(OH)2 materials suggest formation of fine conductive network by homogeneous Ni and Co(OH)2 coating. The capacities of these coated electrodes faded by 25% after 50 charge-discharge cycles. Their swelling rate during cycles was larger than those of the conventional Ni-foam electrodes, and the cycle degradation was mainly attributable to decrease in current collectivity by the swelling. Sealed battery with Co(OH)2-coated Ni(OH)2 showed utilization efficiency of 77% (vs. 0.2 C) at 3 C rate, which was comparable to that of conventional Ni-foam electrode.

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