Construction of a transition-metal sulfide heterojunction photocatalyst driven by a built-in electric field for efficient hydrogen evolution under visible light

Photocatalytic H₂ evolution is of prime importance in the energy crisis and in lessening environmental pollution. Adopting a single semiconductor as a photocatalyst remains a formidable challenge. However, the construction of an S-scheme heterojunction is a promising method for efficient water splitting. In this work, CdS nanoparticles were loaded onto NiS nanosheets to form CdS/NiS nanocomposites using hollow Ni(OH)₂ as a precursor. The differences in the Fermi energy levels between the two components of CdS and NiS resulted in the formation of a built-in electric field in the nanocomposite. Density functional theory (DFT) calculations reveal that the S-scheme charge transfer driven by the built-in electric field can accelerate the effective separation of photogenerated carriers, which is conducive to efficient photocatalytic hydrogen evolution. The hydrogen evolution rate of the optimized photocatalyst is 39.68 mmol·g⁻¹ h⁻¹, which is 6.69 times that of CdS under visible light. This work provides a novel strategy to construct effective photocatalysts to relieve the environmental and energy crisis.