Investigation of photocatalytic performance of CuS/Bi₂WO₆ and degradation pathway of RhB in water

A series of CuS/Bi₂WO₆ composites were synthesized by solvothermal synthesis, which showed enhanced photocatalytic activity. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence ultraviolet–visible absorption spectroscopy, transient photocurrent and EIS. The results showed that as-prepared CuS/Bi₂WO₆ has flower-like nano microspheres self-assembled by nanoplates and CuS nanorods are uniformly dispersed on its surface. The CuS/Bi₂WO₆ forms heterojunctions between CuS and Bi₂WO₆ and shows a wide light response range and a strong light response intensity. The CuS/Bi₂WO₆ exhibits a better Rhodamine B (RhB) degradation effect than pure Bi₂WO₆ and CuS, and it can degrade 90% RhB in 50 min and achieve complete degradation in 70 min under Xe lamp irradiation. The CuS/Bi₂WO₆ has photocatalytic activity in a low pH environment and good stability. The formation of a heterojunction between CuS and Bi₂WO₆ can effectively separate photo-generated electrons and holes, greatly improving the photocatalytic activity. In the CuS/Bi₂WO₆-RhB reaction system, O₂⁻ is the main active species, and it can rapidly remove the ethyl group from the amino group linked to benzene rings to achieve the N-de-ethylation reaction in the process of RhB degradation. The N-de-ethylated products are simultaneously degraded to small organic molecules and even mineralized into CO₂ and H₂O.