Z-scheme heterojunction ZnS/WO₃ composite: Photocatalytic reduction of uranium and band gap regulation mechanism

In the present research, ZnS/WO₃ composites were prepared by coprecipitation method to construct the Z-scheme heterojunction photocatalyst with high efficiency electron separation for the photocatalytic reduction of U(VI). Compared with WO₃ and ZnS, the visible light absorption, photoreduction ability and photocatalytic activity of ZnS/WO₃ composites were improved. The ZnS/WO₃ composites show higher photoreduction U(VI) performance under visible light irradiation with the maximum extraction capacity of U(VI) at 1.52 g g⁻¹. The ZnS/WO₃ composites exhibit high uranium reduction ability under natural light with removal efficiency reaching 93.4 %. In-situ monitoring experiments and DFT calculations were designed to explore the mechanism and pathway of photoelectron transfer in the reduction process from U(VI) to U(IV). The results show that ZnS/WO₃ has an internal electric field to form a Z-scheme electron transfer, and uranium reduction is a dual-electron transfer pathway. In addition, the band gap regulation mechanism of binary composite semiconductor materials is deeply discussed.