Electrocatalysis of oxygen on single crystal gold electrodes

Abstract

Oxide formation and oxygen reduction on gold have been investigated with single crystal electrode surfaces of various orientations. Both reactions show sensitivity to the surface orientation, presence of steps, their density and orientation. The initial stages of oxide formation can be correlated with calculated relative surface energy. Anions exert a pronounced effect on oxide formation. The activity for oxygen reduction can be correlated with the same surface property except for Au(100). Structural effect from this particular plane outweighs the electronic effects. No correlation for alkaline solutions was found. Rotating ring-disc measurements show no hydrogen peroxide generation Au(100) in the presence of almost neutral AuOH-(1 - λ)on the surface. This makes it the most active electrocatalyst for oxygen reduction in alkaline solutions. At more negative potentials (no AuOH on the surface) a series mechanism up to the peroxide stage is operative. The Au(311) plane also shows a high activity dependent on AuOH-(1 - λ). Data for both reactions clearly demonstrate that each crystallographic orientation gives an electrode surface with distinct electrochemical properties.