Radical detection and mechanism of WO3/CeO2 nanocomposite as a visible active photocatalyst

Visible light active photocatalysis by a WO3/CeO2 nanocomposite was studied in this work. The formation of a significant amount of hydroxyl radicals and hydrogen peroxide by the composite was observed under visible light irradiation. The combination of WO3 and CeO2 resulted in a larger amount of OH radicals, hydrogen peroxide and stronger ethylene decomposition ability compared with those of the respective single materials. Consequently, the present WO3/CeO2 system exhibited significant visible photocatalytic mineralization of volatile organic molecules. A possible mechanism for the great enhancement of the photocatalytic properties of WO3 caused by CeO2 in the nanocomposite WO3/CeO2 system is also proposed. Based on ethylene decomposition tests under anaerobic ambient conditions, it was experimentally suggested that the CeO2 does not only contribute through simple charge carrier separation, but also plays another role as an electrons acceptor. There is also some possibility that CeO2 may provide oxygen or superoxide ion (\({\text{O}}_{2}^{{ \cdot - }}\)) through the reversible transition between Ce4+ and Ce3+ by accepting excited electrons from WO3 and adsorbing oxygen from ambient.