Photocatalytic Reactions Involving Radical Chain Reactions Using Microelectrodes

Abstract

The mechanism of photocatalytic decomposition of ethanol in aqueous solution was studied using a microelectrode technique. We employed a partially Pd-covered TiO 2 film as a model for the metal-deposited photocatalyst. We observed concentration changes of dissolved oxygen and H 2 O 2 caused by the photocatalytic reaction in the absence and presence of ethanol separately above the bare TiO 2 and Pd-covered surfaces. It is clearly shown that dissolved oxygen is consumed even on oxidation sites of the photocatalyst in the presence of ethanol, producing H 2 O 2 . On the basis of these results, we conclude that radical chain reactions proceed at oxidation sites (i.e., bare TiO 2 ) but not at reduction sites (i.e., Pd-covered surface) on the photocatalyst.