Structural effects in electrocatalysis: Oxygen reduction on the gold single crystal electrodes with (110) and (111) orientations

Abstract

The kinetics of O2 reduction on the Au (110) and the Au (111) single crystal electrodes have been examined using the rotating disc method. The quality of the surfaces has been determined by Auger electron spectroscopy and LEED. Two electrons are exchanged in O2 reduction on both surfaces. HO2 appears completely stable on the (111) face. The half-wave potential for the Au (110) surface is ca. 70 mV more positive than that for the Au (111) face. The cathodic and anodic kinetic data for the O2/HO2 and HO2−/OH− couples support the mechanism with the following initial two steps: O2+e−→O2−(ads) 2 O2−(ads)+H2O→HO2−+O2+OH− Slow further reduction of HO2−, which occurs on the Au (110) face, is controlled by a chemical reaction. The higher activity of the Au (110) face is explained by some reduction of HO2− on a partially discharged OH−, whose adsorption on the Au (111) face is negligible.