Two-Dimensional ZnS/SnS(2) 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(2) heterojunctions with different stacking models of ZnS and SnS(2) 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(2) heterojunctions have higher carrier mobilities and light absorption intensities than ZnS and SnS(2) monolayers. Therefore, the ZnS/SnS(2) heterojunction has a broad application prospect as a direct Z-scheme visible-light-driven photocatalyst for overall water splitting.