Unusual Postmonolayer Oxide Behavior of Gold Electrodes in Base

Abstract

Gold electrodes in base exhibit an unusual type of reaction in potential sweep experiments in the region between completion of the monolayer oxide film and the onset of regular oxygen gas evolution. A large peak, which was particularly well resolved at elevated temperature, was observed on the anodic sweep; the process involved, which had no counterpart on the cathodic sweep, was attributed to catalytic eyolution of oxygen, the unusually high activity being of a transitory character. The effect was attributed to the high activity of gold cations emerging through defects in the monolayer oxide film; the subsequent loss of activity was postulated to be due to dimerization of the hydrated cations leading to accumulation of less active hydrous Au(III) oxide species. A remarkable feature of the effect was the degree to which the charge associated with this unusual peak was influenced by prepolarizing the electrode at potentials below ca. 0.1 V (reference hydrogen electrode). Certain similarities in behavior between gold and platinum in this area were pointed out.