Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 70 , Issue 11
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  • Takashi MITAMURA, Yuji SAEKI, Yoichi KAMEGAYA, Hidehiko KOBAYASHI
    2002 Volume 70 Issue 11 Pages 850-854
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A new dimensionally stable Ti/(Pt + B2O3)-coated electrode has been created using H3BO3 for the first time. An application liquid, consisting of H2PtCl6·6H2O and various amounts of H3BO3 (5, 10, 20 and 30 mass% with respect to Pt) dissolved in butanol, was applied to a Ti substrate of 1 cm2. The Ti/(Pt + B2O3)-coated electrodes, with 0.2-0.8 mg of Pt, were fabricated by heating the electrode at 250-550°C for 10 min. The result of this fabrication process is a novel coating layer microstructure consisting of a network of fine Pt particles and amorphous B2O3. This novel Ti/(Pt + B2O3)-coated electrode differs significantly from conventional Ti/Pt-coated electrodes. Electrodes fabricated using 0.8 mg of Pt content and 20 mass% H3BO3 at 300°C, had a lifetime of approximately 2400 h in 1 M H2SO4 solution at 1 A cm−2 and 40°C. The high durability of the Ti/(Pt + B2O3) electrodes was found to be due to the suppression of Ti substrate dissolution into the electrolytic bath as a result of the presence of B2O3 on the grains and grain boundaries of the Ti substrate.

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  • Susumu KUWABATA, Masaki NAKAGAWA
    2002 Volume 70 Issue 11 Pages 855-859
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Electrocatalytic activities of a glassy carbon electrode coated with the Prussian blue film (PB | GC) toward reduction of NO, NO2, and NO3 have been tested. Cyclic voltammetry of the PB | GC electrode taken in a solution containing NO2 revealed that a redox reaction due to Prussian blue/Prussian white exhibited catalytic activities for electrochemical reduction of the substrate. Electrolysis of the NO2 solution with the PB | GC electrode at −1.1 V vs. Ag | AgCl gave NH3 production. The amount of NH3 production increased with a decrease in solution pH, indicating that NO species generated from NO2 in acidic solution was a reaction substrate. The NH3 production was also obtained by electrolysis of a solution containing NO3. The electrolysis of a NO gas-saturated solution using the PB | GC electrode produced NH3, as expected, and current efficiencies larger than 98% were obtained at different pH. If NO gas was introduced into the cell during the electrolysis, the constant rate of NH3 production was kept for 5 h.

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  • Takatoshi KUROSAKI, Akira NAKAGAWA, Shuji IIMURA, Sachio YOSHIHARA, Ta ...
    2002 Volume 70 Issue 11 Pages 860-862
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    In this paper Electrophoretic Sol-Gel Deposition was introduced to immobilize the TiO2 photocatalysis. Thus prepared coatings showed quite high-photocalytic activities without successive heat treatment. It is suggested that Non-heated coating showed high-photocalytic activity because it responds effectively for light, which is attributed to the nano-structure of the deposited coating.

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  • Tetsuya IWAGISHI, Yuya NAKATSUKA, Satoshi HARADA, Hiroaki YAMAMOTO, Ko ...
    2002 Volume 70 Issue 11 Pages 863-868
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The effect of addition of ethylene glycol on the electrodeposition of zinc in Lewis basic l-ethyl-3-methylimidazorium bromide (EMIB)-ZnBr2 molten salt at 120°C was investigated by cyclic voltammetry, chronoamperometry and chronopotentiometry. A current loop showing the presence of a nucleation overpotential was observed in cyclic voltammogram for the EMIB-ZnBr2 binary molten salt. Analysis of the choronoamperometric current-time transients indicated that the overpotential was related to the progressive nucleation with diffusion controlled growth of the nuclei. This nucleation loop disappeared on adding ethylene glycol more than 45 mol% to the above binary molten salt. The cathodic current was increased with increasing ethylene glycol content. These effects of ethylene glycol were probably due to the mechanism that ethylene glycol promoted the dissociation of EMIB to EMI+ cation and Br, and accordingly the concentration of ZnBn42− in the molten salt was increased.

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  • Bustam M. AZUMI, Tatsumi ISHIHARA, Hiroyasu NISHIGUCHI, Yusaku TAKITA
    2002 Volume 70 Issue 11 Pages 869-874
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Electrochemical Li intercalation properties in 12-molybdophosphoric and 12-tangstophosphoric acids were investigated. It was found that both 12-molybdophosphoric and 12-tangstophosphoric acids exhibit fairly large capacity for the Li intercalation. Flat potential of 12-tangstophosphoric acids was 0.5 V, which could be used for the anode of Li ion battery. 12-molybdophosphoric acid exhibits the flat potential of 1.5 V, although cycle stability is not high. XRD measurement shows the formation of Li2MoO4 after the intercalation of Li. Therefore electrochemical Li intercalation occurs by redox between Mo6+ and Mo4+ and so the theoretical Li intercalation capacity in 12-molybdophosphoric acid is 373 mAh/g. Ion-exchanging H+ in 12-molybdophosphoric acid to Cs+ is effective to improve the cycle stability and capacity of ca. 200 mAh/g is sustained after 10 cycles. De-intercalation potential of 4.0 V is newly appeared by substitution of Mo in 12-molybdophosphoric acid with V although the capacity is still not large. Therefore, substitution of V is effective for increasing the Li intercalation potential.

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  • Shin-ichi TOBISHIMA, Yoshihiko OGINO, Yu WATANABE
    2002 Volume 70 Issue 11 Pages 875-879
    Published: November 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The influence of additives in electrolyte solutions on overcharge tolerance and cycle life of rechargeable lithium cells is examined. The electrolyte solution employed in this work was 1 M LiClO4-propylene carbonate. The additives we studied were ten organic aromatic compounds. Biphenyl is well-known as an overcharge protection additive. The purpose of this work was to find additives with higher oxidation potential and longer charge-discharge cycle life than biphenyl. Summarizing the results, cyclohexylbenzene and hydrogenated diphenyleneoxide exhibited better performance than biphenyl.

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