Abstract
Electrochemical measurements were performed with Pt and Ni electrodes forming an approximate (macroscopic) point contact with a solid electrolyte, for mixtures of in the temperature range 827 to 950°C and 775 to 924°C, respectively. Steady-state current and impedance spectra vs. overpotential under the different experimental conditions were compared with the theoretical models derived in Part I of this paper. A low-frequency inductive loop in the fourth quadrant of the impedance spectra appearing under certain experimental conditions is consistent with a model for a reaction mechanism involving two adsorbed intermediates. At high anodic overpotentials, the data for Ni electrodes are consistent with the formation of an insulating layer of nickel oxide (NiO) in the electrode/electrolyte interface. Irrespective of the experimental conditions, no effects of diffusion limitations were seen in the impedance spectra. The electrode metal plays a significant role in the overall reaction. For Ni, the results indicate a lower specific electrocatalytic activity for than for the reaction. © 2002 The Electrochemical Society. All rights reserved.
Published Version
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