Type-II CdS/PtSSe heterostructures used as highly efficient water-splitting photocatalysts

The design of two-dimensional (2D) heterostructures (HSs) is an effective method to tune the physical and chemical properties of 2D materials. Using first-principles calculations, we explore the photocatalytic activity of CdS/PtSSe HSs (CPHSs) including CdS/SPtSe HSs (CPHS(S)s) and CdS/SePtS HSs (CPHS(Se)s). The small lattice mismatches and the negative interface formation energies suggest that the CPHSs are feasible, and the small bandgaps guarantee the CPHSs to absorb sufficient visible light. The stacking configurations can hardly affect the electronic structures of CPHS(S)s and CPHS(Se)s, but the contact sides can switch CPHSs between type-I and type-II. The type-I CPHS(Se)s are potential candidates as light-emitting diodes. For the CPHS(S)s, the type-II band alignments promote the spatial separation of photogenerated carriers, and the induced built-in electric fields around the interface region also promote the separation of photoinduced carriers. In addition, the band edges of CPHS(S)s fulfill the thermodynamic requirements for photocatalytic water-splitting, and the solar-to-hydrogen efficiencies are up to 37.5%. All these factors prove the CPHS(S)s are highly efficient photocatalysts to split water.