Enhanced Visible-Light Photoactivity of CuWO<sub>4</sub> through a Surface-Deposited CuO


Several papers have shown that CuWO<sub>4</sub> is active under visible light for water oxidation at an applied potential bias and for organic degradation in an aerated aqueous suspension. In this work, we report that the observed reduction of O<sub>2</sub> on the irradiated CuWO<sub>4</sub> is a multielectron transfer process with the formation of H<sub>2</sub>O<sub>2</sub>. More importantly, the surface modification of CuWO<sub>4</sub> with 1.8 wt % of CuO can increase the activity by approximately 9 times under UV light and by 5 times under visible light, for phenol degradation in aerated aqueous suspension. The catalyst was prepared by a hydrothermal reaction between Cu­(NO<sub>3</sub>)<sub>2</sub> and Na<sub>2</sub>WO<sub>4</sub>, followed by thermal treatment at 773 K. High-resolution transmission electron microscopy revealed that triclinic CuWO<sub>4</sub> (40 nm) was covered by monoclinic CuO (4 nm). Through a combination of photo- and electrochemical measurement, a plausible mechanism responsible for the activity enhancement is proposed, involving an interfacial electron transfer from CuO to CuWO<sub>4</sub> and an interfacial hole transfer from CuWO<sub>4</sub> to CuO

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