Oxygen reduction at the Ag|Gd0.2Ce0.8O1.9 interface studied by electrochemical impedance spectroscopy and cyclic voltammetry at the silver point electrode

Abstract

Reduction of oxygen at the silver point electrode|Gd0.2Ce0.8O1.9 interface was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Measurements were performed in the 500–700°C temperature range, at the atmospheric pressure, in oxygen and in argon/oxygen atmospheres. The results of the experiments are consistent with the mechanism in which the oxygen reduction reaction proceeds through the non-electrochemical adsorption/dissociation step and a two-electron two-step electrochemical reaction with the transfer of the first electron as a rate-determining step. Slow diffusion of oxygen is confirmed by both electrochemical impedance spectroscopy and cyclic voltammetry techniques. New equivalent electrical circuit for the investigated interface is proposed.