Preparation and characterization of Bi₂O₃-Bi₂WO₆ direct Z-scheme heterojunction and photocatalytic reduction of U(VI) under visible light irradiation

According to the energy band theory, Bi(NO₃)₃·5H₂O was used as bismuth source to synthesize Bi₂O₃-Bi₂WO₆ composite photocatalyst materials by hydrothermal calcination. The samples were characterized by means of SEM, XRD, XPS, DRS and EIS, respectively, and the photocatalytic activity was assessed in terms of reduction of U(VI) under visible light irradiation. The results show that the prepared Bi₂O₃-Bi₂WO₆ composite materials exhibit enhanced photocatalytic performance for the photo-reduction of U(VI) than the pure Bi₂WO₆, the optimized photocatalytic efficiency for U(VI) is achieved when the mole ratios of Bi₂O₃ to Bi₂WO₆ is 2.4∶1. The improved photocatalytic activity is ascribed to the direct Z-scheme heterojunction between Bi₂O₃ and Bi₂WO₆, resulting in the rapid interfacial transfer of photoelectron-hole and wide light response range. This work provides a new idea to design and synthesize the photocatalysts with high visible light activity and understand the enhanced photocatalytic reduction mechanism of U(VI).