Reduction of oxygen at the silver point electrode vertical bar Gd0.2Ce0.8O1.9 interface was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Measurements were performed in the 500-700 degrees 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. (C) 2013 Elsevier Ltd. All rights reserved.