Chloride inhibition of ethanol electrooxidation at a platinum electrode in aqueous acid solution

Abstract

The effect of adsorbed chloride ion on the electrooxidation of ethanol at a platinum electrode in 0.5 M H 2SO 4 at 25°C has been studied in order to determine if adsorbed species are important in this electrooxidation. The cyclic voltammogram for this system exhibits three anodic waves, one of which is unusual in that it occurs during the cathodic going potential sweep. The data indicate that adsorbed species are involved in all three waves. Mechanisms proposed in the literature for ethanol electrooxidation are discussed in terms of these results. The most likely mechanism for the first wave during the anodic going potential sweep includes a chemical reaction between chemisorbed CH 3ĊHOH and OH (ads), while a reaction between CH 3CH 2OH (ads) and PtO is involved in the second wave. The cathodic going potential sweep wave is acounted for by the electrooxidation of CH 3CH 2OH (ads) on a surface free of oxide and chemisorbed species.