Enhanced photocatalytic activities of visible-light driven green synthesis in water and environmental remediation on Au/Bi2WO6 hybrid nanostructures

Abstract

A series of Au/Bi₂WO₆ nanocomposites with different weight ratios of Au were fabricated via a hydrothermal combined with a rapid reduction–deposition method. Au/Bi₂WO₆ nanocomposites are proven to serve as selective visible light photocatalysts toward aerobic oxidation of benzylic alcohols and reduction of heavy ions Cr(VI), instead of being nonselective in water. Loading Au NPs greatly enhances the photocatalytic activity of Bi₂WO₆ for the selective oxidation of alcohols and reduction of heavy metal ions. The enhancing effect is dependent on the weight ratios of Au to Bi₂WO₆ in the hybrid nanostructures. The optimal catalysts for alcohol oxidation and Cr(VI) reduction are 2.0 wt% and 1.0 wt% Au/Bi₂WO₆, respectively. Furthermore, we find that loading Au results in an obvious increase in photo-induced generation of charge carriers and active radicals determined by electron spin resonance spectroscopy (ESR). ESR signals denoting photogenerated holes and catalytic activity of alcohol oxidation have a similar dependence on the amounts of Au loading. Besides, the generation and transfer of photogenerated electrons induced by Au loading, as well as the relationship with the photocatalytic activity of Cr(VI) reduction, have been examined using photoelectrochemical characterization. The possible roles of Au deposition in improving the photocatalytic redox activity of Bi₂WO₆ are also discussed.