The influence of pH on reaction pathways for O-2 reduction on the Au(100) face

Oxygen reduction on the Au(100) face was studied by the rotating disk-ring electrode technique in solutions of anions which adsorb strongly on gold (HSO4-/SO42- and/or OH-) over the entire pH range. The specific adsorption of OH- anions, which is a pH dependent process, is found to play the key role in determining the reaction pathways. In the absence of OH- adsorption, for pHs below 6, the reduction of O-2 begins as a 2e-process. Due to the increase in local pH during O-2 reduction, the reaction pathway turns into a 4e-reduction at a certain potential depending on the pH of the solution. For pHs higher than 6, O-2 reduction begins as a 4e-process in the potential region where specifically adsorbed OH- anions are present. Copyright (C) 1996 Elsevier Science Ltd