Reaction Mechanism and Activity of WO₃-Catalyzed Photodegradation of Organic Substances Promoted by a CuO Cocatalyst

WO3 is known as a visible-light-responsive photocatalyst; however, WO3 has low activity for the photodegradation of organic substances in the absence of cocatalysts. The activity of WO3 was significantly improved by the loading of CuO as a cocatalyst, and this catalyst system can be used practically because it is inexpensive and easy to prepare. We investigated the properties of a CuO/WO3 catalyst by means of XPS measurements, electrochemical measurements, and a layered model reaction, and we proposed a reaction mechanism of CuO/WO3 in which CuO promotes oxygen reduction for WO3-catalyzed photodegradation by the Cu(II)/Cu(I) redox reaction. Furthermore, the oxygen reduction reaction over CuO was improved by light irradiation of CuO. The optimized CuO/WO3 photocatalyst showed higher activity for the photodegradation of acetaldehyde than did N-TiO2 and TiO2 under fluorescent-lamp irradiation simulating that used in indoor applications.