Two-Dimensional ZnS/SnS Heterojunction as a Direct Z-Scheme Photocatalyst for Overall Water Splitting: A DFT Study.

Direct Z-scheme photocatalysts have attracted extensive attention due to their strong redox ability and efficient separation of photogenerated electron-hole pairs. In this study, we constructed two types of ZnS/SnS heterojunctions with different stacking models of ZnS and SnS layers, and investigated their structures, stabilities, and electronic and optical properties. Both types of heterojunctions are stable and are direct Z-scheme photocatalysts with band gaps of 1.87 eV and 1.79 eV, respectively. Furthermore, their oxidation and reduction potentials straddle the redox potentials of water, which makes them suitable as photocatalysts for water splitting. The built-in electric field at the heterojunction interface improves the separation of photogenerated electron-hole pairs, thus enhancing their photocatalytic efficiency. In addition, ZnS/SnS heterojunctions have higher carrier mobilities and light absorption intensities than ZnS and SnS monolayers. Therefore, the ZnS/SnS heterojunction has a broad application prospect as a direct Z-scheme visible-light-driven photocatalyst for overall water splitting.