Photocatalytic reduction of Cr(VI) using a wurtzite/natural sphalerite heterostructure: Synergistic effects of exposed active facets, vacancies and a heterophase junction

Highlights: • The heterophase junction of WS accelerates the separation and transfer of photogenerated carriers; • The internal electric field of wurtzite' (0 0 2) active facets improves photogenerated carriers' separation; • the synergistic effects of the exposed active facets, heterophase interface and inherent defects increase vacancies in WS; • The cost of photocatalysts can be greatly reduced using natural sphalerite as raw material. The development of stable and efficient photocatalysts is a basic requirement for photocatalytic treatment of heavy metal pollutants. For this study, a composite photocatalyst (W_xS_1-x) consisting of hierarchical nano-sphere wurtzite with exposed active facets and natural sphalerite was constructed. Optimized as W_0.4S_0.6, it was able to reduce Cr (VI) at an efficiency of 97.11% in 30 min via photocatalysis, which was 4.20 times that of natural sphalerite. The key factors enhancing the photocatalytic performance of WS are the exposed active facets of wurtzite, the heterogeneous transition layer and the inherent mineralization defects of natural sphalerite, all combining to increase vacancies. Furthermore, the separation of photogenerated electrons and holes is more efficient thanks to the built-in electric field induced by the active facets and the heterophase junction, which contributes to the material's overall photocatalytic efficiency. Multiple characterizations were done, revealing the photocatalytic mechanism that was just outlined. This study provides a new approach to constructing high-efficiency and low-cost photocatalysts by combining defect engineering and heterojunction design.