Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 73 , Issue 7
Showing 1-15 articles out of 15 articles from the selected issue
Preface
Communications
Articles
  • Yoshio MATSUZAKI, Yoshitaka BABA, Teruhiro SAKURAI
    2005 Volume 73 Issue 7 Pages 484-488
    Published: July 05, 2005
    Released: June 01, 2019
    JOURNALS OPEN ACCESS

    We have operated the single-cells in the stack structure using methane as a fuel under high fuel utilizations. Methane fuel was supplied directly to the cell-stack after addition of steam at a steam to carbon ratio of 2. A steam-reforming reaction was conducted directly on the anode (direct internal reforming: DIR). In the case of the single-cell with the anode-substrate having relatively high porosity, stack voltage was found to be 0.767 V at fuel utilization of 75%, at which d.c. energy conversion efficiency is 50.2% (H HV). A maximum energy conversion efficiency, 53.6%, was achieved at fuel utilization of 86% and cell voltage of 0.712 V. This methane-to-electricity conversion efficiency will be high enough for practical applications. For anode-supported SOFCs, concentration polarization loss in the anode can be a crucial problem because fresh fuel and electrochemical reaction products have to diffuse through a thick anode substrate in the opposite direction between the flow field (fuel distribution channel) and the anode/ electrolyte interface. Limiting current density with a diluted CO at a fixed current density was measured and analyzed to investigate the diffusion characteristics of a fuel in the anode-substrates. Diffusion parameters obtained by the analysis were verified by measurement of the limiting current density with diluted H2 and voltage response for depolarization process after current-interruption.

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  • Kenji MACHIDA, Hideaki TAKENOUCHI, Remi HIRAKI, Katsuhiko NAOI
    2005 Volume 73 Issue 7 Pages 489-495
    Published: July 05, 2005
    Released: June 01, 2019
    JOURNALS OPEN ACCESS

    A cyclic indole trimer (CIT) was studied electrochemically and was proposed as a new category of redox capacitor electrode material. ln a sulfuric acid aqueous media, the CIT electrode showed electrochemical redox activity at wide potential window between 0 and 1V vs. Ag/AgCl. The wide redox system is attributed to two redox couples, anion doping/undoping with electron transfer and proton undoping/doping. Specific capacity obtained for the CIT electrode was 55 Ah kg-1(198 Fg-1), which is three times higher than that for the polyindole (21 Ah kg-1). More importantly, the CIT electrode maintained its high capacity of 52 Ah kg-1 (187 Fg-1) after 100,000 cycling, while the capacity decreased down to 5 Ah kg-1 for the polyindole electrode.

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  • Katsuhiko NAOI, Yosuke OTA, Kenji MACHIDA
    2005 Volume 73 Issue 7 Pages 496-501
    Published: July 05, 2005
    Released: June 01, 2019
    JOURNALS OPEN ACCESS

    Under a pulse anodization mode, a dielectric Ta2O5 film and a conducting polypyrrole film were formed on a nanoporous Ta pellet anode (average pore size: 250 nm, specific surface area: 4,000 cm2 g-1, capacitance: 50,000μFV g-1). At a first pulse, Ta metal was anodized to form dielectric Ta2O5 nano film (1.6~ 14 nm in thickness) on nano-porous Ta pellet. With subsequent pulses, the polypyrrole film was deposited uniformly and compactly (average thickness: 70~230 nm) on the Ta2O5/Ta nano-porous layer. The thickness of polypyrrole film was controlled by tuning current and charge of the pulse. The polypyrrole film on the Ta2O5/Ta nano-porous layer showed low resistivity of 2×10-1Ω persquare. By AC impedance analysis, low equivalent series resistance (400 mΩ at 100 kHz) was demonstrated for a sample electrolytic capacitor with nano-porous Ta2O5/Ta anode with polypyrrole coating layer.

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