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

Production of H 2 O 2 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/WO 3 under visible light in presence of methanol. The production of H 2 O 2 was greatly promoted by A (Ni 2+ , PO 4 3− , CO 3 2− , and F − ), slightly increased by B (SO 4 2− , NO 3 − , Cl − , and ClO 4 − ), greatly inhibited by C (Cu 2+ , and Fe 3+ ), and slightly decreased by Co 2+ . Moreover, the effect of Ni 2+ was weakening by F − , and vice versa. Analysis showed that Ni 2+ was oxidized into Ni 3+ , reactive to methanol, not to water. On Au/WO 3 electrode, anions A inhibited O 2 reduction, and promoted methanol photo-oxidation, while all anions had little influence on the pathway of O 2 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 O 2 .