Effect of inorganic ions on H2O2 production over illuminated Au/WO3 with visible light

Abstract Production of H2O2 via semiconductor photocatalysis has received an increasing attention. Herein the effects of cations in perchlorate form and anions in sodium form are examined. Experiment was conducted with Au/WO3 under visible light in presence of methanol. The production of H2O2 was greatly promoted by A (Ni2+, PO43−, CO32−, and F−), slightly increased by B (SO42−, NO3−, Cl−, and ClO4−), greatly inhibited by C (Cu2+, and Fe3+), and slightly decreased by Co2+. Moreover, the effect of Ni2+ was weakening by F−, and vice versa. Analysis showed that Ni2+ was oxidized into Ni3+, reactive to methanol, not to water. On Au/WO3 electrode, anions A inhibited O2 reduction, and promoted methanol photo-oxidation, while all anions had little influence on the pathway of O2 reduction. A plausible mechanism is proposed, involving the hole oxidation of anions (not F−), followed by methanol oxidation. This work highlights the importance of inorganic ions to the selective reduction of O2.