OXIDATION OF SOME REDUCING AGENTS USED IN ELECTROLESS PLATING BATHS AT GOLD ANODES IN AQUEOUS-MEDIA

The oxidation of four reductants, two of direct interest in electroless plating baths, at gold electrodes in base was investigated using cyclic voltammetry and the results were interpreted in terms of the incipient hydrous oxide model of electrocatalysis. Dimethylamine borane and tert-butylamine borane reacted in a similar manner; the results were interpreted in terms of the oxidation of the hydroxytrihydroborate anion; potential/pH studies indicate that the important mediator at the interface for this reaction is a cationic, Au(I), species. Pyridine borane reacted in a significantly different manner; the mediating species in this case appeared to be an Au(III) hydrous oxide; further work is required to explain the behaviour of this system. The oxidation of hypophosphite on gold in base was quite sluggish, as was the oxidation of hypophosphorous acid at low potentials in solutions of low pH; it was assumed here that in this system there is a complication due to phosphorous atoms adsorbing at, and thus deactivating, the gold surface.