MULTISTEP ONE-ELECTRON PHOTOELECTROCATALYTIC REDUCTION OF OXYGEN AT TRIS(2,2'-BIPYRIDINE)RUTHENIUM(II)-INCORPORATED NAFION(R)-COATED AND CLAY-COATED ELECTRODES IN THE PRESENCE OF MACROCYCLIC COBALT(III) COMPLEXES

The electrocatalytic reduction of oxygen was carried out at Nafion(R)- and clay-modified electrodes in the presence of tetraazamacrocyclic c obalt(III) complexes. Long-time electrolysis experiments were performe d, and the faradaic yield of H2O2 and the rate of H2O2 production were found to be higher at clay-coated electrodes than at Nafion(R)-coated electrodes. In the case of the photoelectrocatalytic reduction of oxy gen at Pt/Nafion(R)/[Ru(bpy)(3)](2+) and Pt/H+-montmorillonite/[Ru(bpy )3](2+) electrodes, the amounts of H2O2 produced increased by a factor of two under light irradiation condition when compared to dark. The f aradaic yield of H2O2 under irradiation conditions was determined at t he modified electrodes, and a mechanism for multistep one-electron pho toelectrocatalytic reduction of oxygen was proposed. (C) 1998 Elsevier Science S.A. All rights reserved.