A rotating ring-disk electrode (RRDE) method is herein described for studies of O2 evolution on nickel hydrous oxide films, NiOx(hydr.), electrodeposited on the gold disk of a Au-Au RRDE in aqueous 1.0 M KOH. This technique relies on the quantitative detection of O2 generated at the NiOx(hydr.)|Au disk electrode during a linear potential scan, by the concentric, bare Au-ring electrode, which can then be used to determine contributions to the disk current (Idisk) derived solely from O2 evolution. Subtraction of such contributions from Idisk in the potential range positive to the trailing edge of the peak ascribed to the oxidation of the NiOx(hydr.) film revealed a constant, positive current when the voltage was scanned in the positive direction, and a constant, negative current, albeit of smaller magnitude, in the subsequent scan in the negative direction. This observation suggests that once account is made for O2 evolution, the NiOx(hydr.)|Au-electrolyte interface in that potential range (0.5-0.65 V vs. Hg|HgO,OH-), behaves as a (pseudo) capacitor, a model that was further confirmed by monitoring the current as a function of the scan rate. The actual values of this pseudocapacitance were found to be on the order of ca. 80 kF mol-1 Ni sites in the film (or equivalently, ca. 0.1 e- per Ni site within the potential range specified above) and, thus, very similar to those reported earlier based on current interruption-potential decay and impedance measurements for O2 evolution on NiOx(hydr.) grown on Ni electrodes. Implications of these results to the mechanism of self-discharge of NiOx(hydr.) electrodes for alkaline secondary batteries are discussed.
|ジャーナル||Journal of Electroanalytical Chemistry|
|出版ステータス||Published - 1999 6月 17|
|イベント||Proceedings of the 1998 International Symposium on New Trends in Electroanalytical Chemistry - Seoul, S Kor|
継続期間: 1998 9月 10 → 1998 9月 12
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