Theoretical Resolution of the Exceptional Oxygen Reduction Activity of Au(100) in Alkaline Media

The reason that Au(100) surfaces have exceptional activity toward the oxygen reduction reaction (ORR) in alkaline media has been a long-standing puzzle that remains unexplained. Theoretically, the high activity of Au(100) cannot be understood entirely by the widely employed computational hydrogen electrode method, because oxygen adsorption on Au(100) is calculated to be too weak. Here we present a density functional theory study of the electrochemical Au(100)/aqueous interface under constant potential conditions. Calculations of how the adsorption energies of the ORR intermediates vary as a function of applied potential and pH show that *O2H can be stabilized in alkaline media as compared to acidic media, leading to enhanced ORR activity. Adsorbed *OH can further stabilize *O2H adsorbed at a nearest neighbor site leading to the favorable 4e(-) reduction pathway and an onset potential of 0.81 V vs the reversible hydrogen electrode. These results provide a direct comparison to experiments and insight into the influence of the electrochemical interface on the ORR energetics.