AN INVESTIGATION OF THE ELECTROCATALYTIC BEHAVIOR OF GOLD IN AQUEOUS-MEDIA

A survey was carried out on the electrocatalytic behaviour of gold, both for oxidation and reduction processes, mainly with regard to aqueous solutions of low pH. The results were interpreted in terms of the adatom-incipient hydrous oxide mediator mechanism of electrocatalysis; the important mediator for oxidation was considered to be a very low coverage Au(III) species which, as in base, can exist in two different forms. Agreement with regard to premonolayer formation potential values on changing from base to acid was excellent, providing that the process involved is assumed to exhibit a super-nernstian shift commonly observed with hydrous oxide systems. The mediation process is less effective with gold in acid as compared with base and with some organics the oxidation currents in acid exhibited significant decay with time under constant potential conditions. The reduction of persulphate was inhibited, apparently because of product adsorption at Au(I) cationic sites.