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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. [Display omitted] • The electronic, optical, and photocatalytic properties of 2D CdS/PtSSe heterostructures are studied. • The CdS/PtSSe heterostructures could switch between type-I and type-II by the change of contact sides. • The CdS/SPtSe heterostructures are promising water-splitting photocatalysts with the solar-to-hydrogen efficiency of 37.5%. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) Z-scheme photocatalytic systems can usually achieve high catalytic efficiencies by separating the photoinduced carriers attend water redox reaction at different positions and providing much stronger overpotentials to drive water redox reaction. However, it is filled with challenges to develop Z-scheme photocatalysts (PCs) due to the strict requirement of proper band edge alignment and built-in electric field. Based on hybrid density functional, the photocatalytic properties of CdO/PtSSe heterojunctions (HJs) including CdO/SPtSe and CdO/SePtS HJs are investigated. The analysis of electronic structures, work functions, and charge transfer suggest the proper band alignments and the existence of built-in electric field from CdO to PtSSe, confirming the Z-scheme photocatalytic mechanism of CdO/SPtSe and CdO/SePtS HJs. The light absorption curves show that CdO/SPtSe and CdO/SePtS HJs could harvest sufficient solar light. Furthermore, both CdO/SPtSe and CdO/SePtS HJs can provide sufficient overpotentials to finish water redox reaction. These findings indicate that CdO/SPtSe and CdO/SePtS HJs are promising water-splitting PCs. • The small bandgaps promote the CdO/SPtSe and CdO/SePtS HJs to utilize sufficient solar light. • Both CdO/SPtSe and CdO/SePtS heterojunctions are both direct Z-scheme photocatalysts. • The heterojunctions could provide sufficient driving force to finish the HER and OER processes. [ABSTRACT FROM AUTHOR]