First principles study on photocatalytic water decomposition of ZnO/WS2 heterojunctions

Abstract

The generation of clean energy hydrogen through solar-driven water decomposition is an effective solution to the current global energy shortage and environmental pollution. In this paper, ZnO/WS₂ heterojunction is constructed based on first-principles. The effect of uniaxial strain and vacancy defects (V_Zn, V_O, V_S, V_2S) on electronic and optical properties of ZnO/WS₂ heterojunction are calculated. The results indicate that the bandgap of the heterojunction is decreased and the visible absorption range is expanding. Additionally, the built-in electric field of the heterojunction is determined to be oriented from ZnO to WS₂, which enhances the efficiency of carrier separation. Band-edge position analysis indicates that ZnO/WS₂ heterojunctions exhibit good redox water properties under an applied compressive strain of −2 %. Finally, the visible light absorption range of the heterostructures is also expanded by introducing V_S and V_2S vacancy defects. However, it exhibits a superior ability to oxidize and reduce water only under V_Zn defects. The corresponding photocatalytic mechanism of ZnO/WS₂ heterojunctions is discussed.