화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.149, No.12, E506-E514, 2002
Electrochemical oxidation of CO on Pt and Ni point electrodes in contact with an yttria-stabilized zirconia electrolyte - II. Steady-state and impedance measurements
Electrochemical measurements were performed with Pt and Ni electrodes forming an approximate (macroscopic) point contact with a solid electrolyte, (Y2O3)(0.08)(ZrO2)(0.92), for mixtures of CO-CO2 in the temperature range 827 to 950degreesC and 775 to 924degreesC, 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 CO-CO2 than for the H-2-H2O reaction.