Size effect of zinc oxide-supported gold nanoparticles on the photocatalytic activity for two-electron oxygen reduction reaction

UV-light irradiation of gold nanoparticle-loaded ZnO with a heteroepitaxial junction (Au#ZnO) in aerated ethanol aqueous solution gives rise to two-electron oxygen reduction reaction (ORR) to yield more than 1 mM hydrogen peroxide at only 1-h irradiation. The photocatalytic activity has been revealed to remarkably increase with increasing Au particle size as the result of the increase in H2O2 formation rate and the decrease in its decomposition rate. The outstanding photocatalytic activity of Au#ZnO can mainly stem from the enhancement of charge-separation and the reduction in the loss of H2O2 by the non-adsorptivity of ZnO.