Cyclic voltammetric studies on the reduction of a gold oxide surface layer

Abstract

Cathodic reduction of a stationary surface layer of gold compounds formed anodically on a gold electrode in 0.5 M H 2SO 4 solution at E=1.7 V, i.e. prior to oxygen evolution, has been investigated. With the initial amount of gold oxide on the electrode surface being constant, linear dependences of j p on v, log j c on E and log j p on E p were established. It has been found that the parameters d E/d log j c, d E p/d log j p and d E p/d log v at 1.2 V (SHE)> E> E p are close to the theoretical value of 2.3 R T/ F. Such Tafel behaviour is expected for the cathodic process in the case of a reversible metal|metal oxide electrode. It has been proposed that the reversibility of the cathodic process may be determined by the equilibrium of the following surface reaction: Au · H 2O+2H 2O⇔(Au(OH) 3) s+3H ++3e − where Au ·H 2O represents the gold surface atoms with electrostatically adsorbed H 2O, and (Au(OH) 3) s is Au(OH) 3 in the form of the surface layer. This equilibrium may exist at the interface only when the Au(OH) 3 layer is present on the electrode surface. The equilibrium potential of this reaction was evaluated as 1.28±0.01 V.