First-Principles Study on Direct Z-Scheme SnC/SnS2 Heterostructures for Photocatalytic Water Splitting

Direct Z-scheme heterojunctions are known for their unique carrier mobility mechanism, which significantly improves photocatalytic water splitting efficiency. In this study, we use first-principles simulations to determine the stability, electrical, and photocatalytic properties of a SnC/SnS2 heterojunction. Analyses of the projected energy band and state density demonstrate that the SnC/SnS2 heterojunction exhibits an indirect band gap of 0.80 eV and a type-II band alignment. Analysis of its work function shows that the SnC/SnS2 heterojunction has a built-in electric field pointing from the SnC monolayer to the SnS2 monolayer. The band edge position and the differential charge density indicate that the SnC/SnS2 heterostructure exhibits a Z-scheme photocatalytic mechanism. Furthermore, the SnC/SnS2 heterojunction exhibits excellent visible-light absorption and high solar-to-hydrogen efficiency of 32.8%. It is found that the band gap and light absorption of the heterojunction can be effectively tuned by biaxial strain. These results demonstrate that the fabricated SnC/SnS2 heterojunction has significant photocatalysis potential.