Direct Z-scheme SnS₂/WTe₂ heterojunction for enhanced visible-light-driven water splitting performance based on DFT

The use of fossil fuels leads to environmental issues such as global warming and acid rain. Photocatalytic hydrogen production has become a trend towards solving this problem. However, the rapid recombination of photo-generated electrons and holes in single-component photocatalysts severely limits their photocatalytic performance. Van der Waals (vdW) heterojunctions can effectively suppress the carrier recombination rate. Therefore, this study constructs SnS₂/WTe₂ van der Waals heterojunctions via a vertical stacking approach and employs first-principles calculations to investigate their stability, electronic structure, optical properties, and photocatalytic mechanisms. The results demonstrate that the SnS₂/WTe₂ heterojunction exhibits structural stability, with the valence band maximum (VBM) and conduction band minimum (CBM) dominated by WTe₂ and SnS₂, respectively. The oxidation and reduction potentials of this heterojunction span the redox potential of water, enabling photocatalytic water splitting to proceed normally. Compared to the single-layer materials, the SnS₂/WTe₂ heterojunction exhibits superior light absorption properties and refractive index. Furthermore, it achieves a hydrogen production efficiency of 9.39 % under AM1.5G solar flux. The application of biaxial strain further optimizes the electronic and optical properties of the SnS₂/WTe₂ heterojunction. The SnS₂/WTe₂ heterojunction exhibits efficient HER and OER performance based on Gibbs free energy calculations. This study provides a highly promising candidate material for the development of high-efficiency hydrogen evolution reaction catalysts.