Z-scheme NiS@ZnCdS heterostructures and their boosted photocatalytic H2 evolution

Abstract

Due to exceptional photocatalytic hydrogen evolution properties, ZnCdS is considered as a promising strategy to enhance the photocatalytic hydrogen evolution performance of ZnCdS with introducing sulfur vacancy or constructing heterostructures. Here, sulfur vacancy-rich ZnCdS nanoparticles were synthesized via a straightforward co-precipitation method followed by a high-temperature annealing treatment. Then NiS@ZnCdS composites were prepared with the hydrothermal method after mixed the precursors of Ni(Ac)₂·2H₂O and CH₄N₂S with the prepared Zn_0.5Cd_0.5S powders. Thereafter, the prepared samples were used as photocatalysts for hydrogen production. The results showed that the optimized NiS@ZnCdS heterostructures has a photocatalytic hydrogen production rate of 42 mmol · g⁻¹·h⁻¹, which is 14 times higher than that of the ZnCdS sample without annealing treatment. The mechanism behind has been analyzed. A staggered band energy alignment between NiS and ZnCdS was constructed from the measurements of ultraviolet photoelectron spectroscopy (UPS) and XPS spectra, and a z-scheme charge transfer mode was proposed between NiS and ZnCdS with an assistance of electron spin resonance (ESR) signals of •O₂⁻. The z-scheme heterostructure between NiS and ZnCdS can enhance the separation of photogenerated electron-hole pairs and increase the photocatalytic activity. The studies will be helpful to construct the NiS related heterostructure.