Hydrogen peroxide formation in oxygen reduction at gold electrodes: II. Alkaline solution

Abstract

Oxygen reduction at au electrodes in alkaline solutions is studied using a rotating disk electrode with a concentric ring. At low current densities, the tafel slope is close to −0.036 V; at high. Current densities it is close to −O.100 V. pH-dependence of potential is +0.020 V ( vs. H.E.). Hydrogen peroxide which forms at the electrode reduces only partially to water. The rate of its reduction appears to be potential-independent. Two alternative accounts of the observed kinetics are given. In the first, the second charge transfer step in a considered reaction path is the rate-controlling step. In the second, the log i- V relationship is determined by the rate of diffusion of hydrogen peroxide away from the electrode surface, rather than by a step involving an electrode reaction. For the reduction of hydrogen peroxide, a chemical step that is not preceded by a charge transfer step is the rate-controlling step.