Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 69 , Issue 7
Showing 1-15 articles out of 15 articles from the selected issue
Vision
Comprehensive Paper
  • Yasuhiro SHIMIZU, Kazuya OGAWA, Yoshihiro AKAI, Takeo HYODO, Yuji TAKA ...
    2001 Volume 69 Issue 7 Pages 508-515
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Behavior of microwave-induced (MI) Ar plasma generated from SiC ceramics in flowing Ar containing trichloroethylene (TCE) or trichlorotrifluoroethane (CFC 113) and the decomposition of TCE and CFC 113 by MI Ar plasma have been investigated systematically under atmospheric pressure. Both TCE and CFC 113 could be decomposed satisfactorily by MI Ar plasma with relatively low energy consumption, if an appropriate amount of O2 was added to the feed gas. These results offer potential advantages of MI Ar plasma for decomposing toxic halogenated hydrocarbons under atmospheric pressure. The notable features of the MI Ar plasma decomposition in an atmospheric Ar stream, in comparison with a thermal, surface discharge, and electron-beam method, has been discussed from the standpoints of byproduct concentrations and electrical energy consumption.

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Communication
  • Masaki YOSHIO, Yongyao XIA, Tetsuo SAKAI
    2001 Volume 69 Issue 7 Pages 516-518
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Manganese spinel without oxygen-deficiency loses capacity only in the high-voltage region during cycling at room temperature, whereas the capacity loss occurs in the both low and high-voltage regions for the oxygen-deficient spinel. The capacity loss is linked to the phase transition (from two-phase to one phase) in the high-voltage region for the oxygen-stoichiometric spinel. Low-temperature XRD and DSC analyses show that the oxygen-rich spinel did not undergo a phase transition from cubic to orthorhombic (or tetragonal) symmetry close to room temperature, whereas the phase transition was observed only in the oxygen-deficient spinel despite whether it is lithium-rich or lithium-deficient.

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Technical Papers
  • Bin YANG, Kensuke ARAI, Fumiyo KUSU
    2001 Volume 69 Issue 7 Pages 519-525
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    The first oxidation potentials of a series of structurally related flavonoids, mostly having hydroxyl substituents, were investigated by employing cyclic voltammetry and flow-through column electrolysis. The flow-through column packed with carbon fibers was useful for determining the half-wave potential (E1/2) of the flavonoids and the number of electrons (n-value) transferred in the oxidation process. The potentials of the flavonoids were shown to be strongly dependent on their structures. The important determinants for the ease of oxidation are : 1) ortho-trihydroxyl group (pyrogallol group) ; 2) ortho-dihydroxyl group (catechol group) ; 3) the presence of a 2,3-double bond in conjugation with 4-oxo and 3-hydroxyl groups ; and 4) another addition of a resonance-effective substituent. The relation between the E1/2 values of the first oxidation step obtained from the hydrodynamic voltammograms and the antioxidant data (IC50) in biological systems obtained from references was examined to determine whether the E1/2 value was an indicator of the biological activity. It was found that more negative E1/2 values of flavonoids were usually associated with decreasing IC50 values. These findings suggest that the electrochemical properties of the flavonoids contribute to their antioxidant activity, and thus the E1/2 values of flavonoids can be used as indices of their antioxidant activities in biological systems.

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  • Shuhua MA, Hideyuki NOGUCHI
    2001 Volume 69 Issue 7 Pages 526-529
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Fe doped Li2Ti3O7 has been prepared from TiO2, LiCH3CO2 • 2H2O and FeOOH. Single-phase compounds with rams-dellite structure were obtained by the heating at 950-1050°C. Fe doping decreases the formation temperature of rams-dellite phase. The limit of Fe doping to Li2Ti3O7 at 1000°C is y ( = e/(Fe + Ti) in atomic ratio) = 0.265. The Rietveld refinement shows that Fe doping did not affect the size of lattice. The results of electrochemical test show that Fe doped Li2Ti3O7 involves two redox reaction of Fe3+/Fe2+ couples and Ti4+/Ti3+ couples. The former reaction proceeds in the voltage range from 2.6 V to 1.5 V, and the latter one follows it. This is strongly supported by the agreement of calculated capacity based on Fe content with experimental one. Total discharge capacities of samples in the first cycle are 110-140 mAh/g for y≦0.189 and samples prepared at lower temperature show slightly higher capacities. All samples show excellent cycling performance.

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  • Shinji HIGASHIKA, Kenzo KIMURA, Yoshiaki MATSUO, Yosohiro SUGIE
    2001 Volume 69 Issue 7 Pages 530-535
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Polyaniline (PANI)-intercalated graphite oxides (GOs) were prepared by the reaction of surfactant-intercalated GO with PANI in N-methyl-2-pyrrolidone. After the interlayer space of GO was saturated by PANI (PANI/GO = 1.5∼1.8), excess PANI particles were deposited on the surface of intercalation compounds. Two types of PANI-intercalated GOs with zigzag and planar type PANI chains were obtained depending on the oxygen contents in graphite oxides. Three types of reactions; intercalation-deintercalation of lithium ion into partially decomposed GO stabilized by PANI and PANI containing partially decomposed GO as a counter polyanion, that of perchlorate ion into PANI occurred for these intercalation compounds after the first charge-discharge cycle. The increase of oxygen content lead the increase of the capacity of the first reaction and the discharge capacities at the 15th cycle reached 118 mAh/g for PANI1.8GO. The deposition of excess PANI particles or the surface of the intercalation compounds also increased the capacity of the above reaction and the discharge capacity reached 134 mAh/g when the surface area of PANI1.8GO was completely covered by PANI particles.

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  • Koji KATAHIRA, Hiroshige MATSUMOTO, Hiroyasu IWAHARA, Norihiko FUKATSU ...
    2001 Volume 69 Issue 7 Pages 536-541
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    A self-referenced electrode was devised for galvanic cell-type hydrogen and steam sensors. Two proton-conducting solid electrolyte discs with porous platinum electrodes, one for electrochemical pumping of hydrogen and the other for sensing of hydrogen or water vapor, were stacked and exposed to test gases at 500-600°C; a small open pore was provided in the sensing electrolyte. When a constant current was sent to the pumping cell to draw out hydrogen at the interface of the two cells, the sensing cell indicated EMF as a function of hydrogen or water vapor activity in the test gas. This suggest that the hydrogen activity at the interface could be controlled with respect the test gas atmosphere, based on the equal rate of the hydrogen pumping and hydrogen or water vapor diffusion through the pore at the stationary state.

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Technological Report
  • Jung-Hwan NA, Yoshihisa KOGO, Kazuya MURAKAMI, Isao TARI
    2001 Volume 69 Issue 7 Pages 542-546
    Published: July 05, 2001
    Released: September 25, 2019
    JOURNALS OPEN ACCESS

    Graphite anode covered with titanium lattice (hybrid electrode) was found to be used as an anode in a large scale process of manufacturing electrolytic manganese dioxide (EMD) by electrolysis of MnSO4-H2SO4 solution using graphite anode and cathode, due to easy removal of deposited EMD from the anode surface without any mechanical destruction of the anode, which was very difficult in the case of using only graphite as an anode. The electrolysis at 75°C provided an advantage of protecting the graphite anode from electrochemical corrosion in addition to heat enegy saving compared with electrolysis at 95°C. Another electrolysis at 75°C was done on a suspension bath process using titanium anode and MnSO4-H2SO4 solution with and without suspended EMD powder. The electrode in a suspesion bath was found to work for a long time without passivasion during electrolysis due to the surface modification by means of the suspended particles, while in nonsuspended bath it was passivated immediately during electrolysis. These results show that the hybrid electrode, and the titanium electrode in the suspension bath process can be used for large-scale EMD production at 75°C.

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Techniques in Electrochemical Measurements
The 20th Kako Memorial Lecture
Salon
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