Oxygen reduction on Au (100) and vicinal Au (910) and Au (11, 1, 1) faces in alkaline solution. A rotating disc-ring study

Abstract

The kinetics of oxygen reduction have been studied on Au (100) and vicinal Au (910) and Au (11, 1, 1) faces in 0.1 M NaOH by a rotating disc-ring method. A very high activity of these surfaces for O2 reduction was demonstrated. The reaction involves a four-electron reduction without HO2- reaching the ring electrode in the presence of the AuOH-(1-λ2) layer on the Au (100) surface. At more negative potentials, as θAuOH → 0, a four-electron reduction takes place in an interactive pathway, followed by a two-electron series pathway and, at very large overpotentials, by a four-electron series pathway. The first electron transfer is the rate-determining step for all three faces. For vicinal faces, the region of the four-electron reduction is reduced due to the smaller region of AuOH formation. Evidence for the surface diffusion of HO2- was found from analysis of the disc-ring data. There were also indications for the splitting of the OO bond by AuOH in the region of the four-electron reduction. Maps of the reaction pathways have been constructed.