Construction of novel ZnO/Ga2SSe (GaSe) vdW heterostructures as efficient catalysts for water splitting

Type-II heterostructures constructed from two-dimensional semiconductor materials have been proved to be an effective way to solve the environmental crisis. In this work, the stability and photocatalytic properties of the novel ZnO/Ga2SSe and ZnO/GaSe heterostructures are demonstrated by DFT calculation. Theoretical results confirm that their band gap widths and band edge positions are consistent with photocatalytic water splitting. The Gibb free energy in the redox process confirm the oxygen reactions of two heterostructures are thermodynamic spontaneous. Moreover, only the ZnO/Ga2SSe heterostructure containing S vacancies could proceed spontaneously during the hydrogen evolution reaction. Subsequently, the two heterostructures are tuned by introducing strain, and the results show that the ZnO/Ga2SSe heterostructure with -2% compressive strain has superior absorption performance in near- UV area. More importantly, the ZnO/Ga2SSe heterostructure has a fairly high solar hydrogen (STH) efficiency (25.05%), remarkably greater than that of pristine ZnO (3.78%) and Ga2SSe (4.16%). In conclusion, the ZnO/Ga2SSe heterostructure can be a prospective alternative material in water splitting.