Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 71 , Issue 7
Showing 1-41 articles out of 41 articles from the selected issue
Vision
Headline
  • Yoshio UMEZAWA, Takashi ITO
    2003 Volume 71 Issue 7 Pages 522-529
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    A new approach to chemical imaging was reported by the group of Umezawa in 1998, utilizing scanning tunneling microscopy (STM) with chemically modified tips. Just as in electrochemistry, electron transfer through the overlap of electronic wave functions of tip and sample surfaces plays a central role in STM, which relies on the tunneling effect as operating principle. This similarity and the success of chemically modified electrodes suggested us that "tailored" chemical modification of STM tips should allow the control of electron tunneling through rational use of chemical interactions. The chemical imaging was obtained from a distinctive chemical affinity between the imaging tip and the substrate, such as hydrogen bond and metal coordination interactions that enhanced the electron tunneling. This technique allows imaging of specific surface species at atomic/molecular resolution and will become a powerful method for fundamental chemical studies at molecular level.

    Download PDF (1128K)
Articles
  • Huan QIAO, Toshiyuki NOHIRA, Yasuhiko ITO
    2003 Volume 71 Issue 7 Pages 530-535
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    Electrochemical behavior of oxide ion at a glassy carbon electrode in a LiF-NaF-KF eutectic melt was investigated by cyclic voltammetry and chronopotentiometry at 753-823 K. The gases produced by potentiostatic electrolysis at 3.0 V (vs. K+/K) were confirmed as CO2 and CO by IR spectroscopy and gas chromatography. The anodic reaction of oxide ion was found to be an irreversible process. The diffusion coefficient of oxide ion as a function of temperature was expressed as: DO2− = 1.3×10-2 exp(−3.9×104/RT)cm2 s-1. The potential sweep method was proved to be useful for monitoring the oxide ion concentration.

    Download PDF (754K)
  • Masayuki ITAGAKI, Hajime HASEGAWA, Kunihiro WATANABE, Toshinori HACHIY ...
    2003 Volume 71 Issue 7 Pages 536-541
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    The oxygen reduction on Ag electrode in the alkaline solution has been investigated by a channel flow double electrode (CFDE). The HO2- emitted from the Ag working electrode can be detected by the collecting electrode at the downstream of the working electrode. The average number of electron transfer in oxygen reduction was determined from the working and collecting electrode currents of CFDE. The final products of the oxygen reduction on the polished Ag electrode in the alkaline solution are OH- and HO2-, and the values of are between 2 and 4. In the present paper, it was found that the n"̅ is close to 4 on Ag electrode pre-oxidized at the potential for AgO formation. The influence of pre-oxidation for Ag electrode on has been discussed. Furthermore, electrochemical impedance was measured to investigate the surface condition of the pre-oxidized Ag electrode. The electrochemical impedance of Ag during oxygen reduction shows an inductive semicircle on the complex plane, indicating the indirect 4-electron reduction.

    Download PDF (629K)
  • Yoshitsugu SONE, Xingjiang LIU, Takefumi INOUE, Xianming WANG, Saburo ...
    2003 Volume 71 Issue 7 Pages 542-548
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    We performed a cycle test with 25% and 40% depth of discharge (DoD) using 30 Ah prismatic Lithium-Ion secondary cells designed for ground applications. For 25% DoD, we observed adequate cycle performance exceeding 18,000 cycles. For 40% DoD, the end of discharge voltage (EoDV) decreased to 3.0 volt after 10,000 charge-discharge cycles, which enabled us to disassemble the cell and check the reason of performance degradation. Through the analysis, we found that the reduced cell performance mainly caused by capacity loss in the negative electrode, especially in the middle of the cell stack. The positive electrode also degraded slightly, and the impedance of the positive electrode increased. The discharge capacity during the 40% DoD test might not be restored by simulated low Earth orbit cycling because of these degradations.

    Download PDF (892K)
Technological Report
  • Choong-Gon LEE, Takashi ITOH, Mohamed MOHAMEDI, Minoru UMEDA, Isamu UC ...
    2003 Volume 71 Issue 7 Pages 549-554
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

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

    Download PDF (718K)
Note
  • Bui T. LUONG, Atsushi NISHIKATA, Tooru TSURU
    2003 Volume 71 Issue 7 Pages 555-557
    Published: July 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    Scanning Electrochemical Microscope (SECM) has been applied to study pitting corrosion of iron in a 50 mM NaCl solution at pH 8.4. In order to monitor pitting propagation, a platinum wire of 10 μm in diameter sealed in Pyrex glass tube was used as an ultra micro probe (tip electrode). In order to detect Fe3+ ion flux emitted from a pit mouth, the tip electrode was placed 5 μm above the pit and polarized at −0.4 V vs. Ag/AgCl/3 M KCl reference electrode so that the Fe3+ ion is reduced to Fe2+ on the surface. The Fe3+ ion was successfully detected on the tip electrode surface.

    Download PDF (397K)
Special Articles
 
Q & A Electrochemistry and Electrochemical Measurement
The 22nd Memorial Lecture
ECSJ News
feedback
Top