S-vacancy-assisted fast charge transport and oriented ReS2 growth in twin crystal ZnxCd1−xS: an atomic-level heterostructure for dual-functional photocatalytic conversion

Abstract

The achievement of dual-functional photocatalytic technology requires a photocatalyst with accelerated charge flow and purposeful active-site arrangement. In this study, we developed an oriented embedding strategy to induce ReS₂ growth at the S vacancy in twin-crystal Zn_0.5Cd_0.5S solid solution (Sv-ZCS), obtaining an atomic-level heterostructure (ReS₂/Sv-ZCS). The electronic structure calculations demonstrate that the charge density of the Zn atom around the S vacancy is higher than for other Zn atoms and the introduced S vacancy establishes a high-speed channel for electron transport via formed Zn–S–Re bonds at the interface between ReS₂ and Sv-ZCS. Photogenerated electrons and holes gathered on Re atoms and Sv-ZCS, respectively, which achieves spatial charge separation and separated arrangement for redox sites. As a result, the optimized ReS₂/Sv-ZCS heterostructure possesses high efficiency of electron injection (2.6-fold) and charge separation (8.44-fold), as well as excellent conductivity capability (20.16-fold). The photocatalytic performance of the ReS₂/Sv-ZCS composite exhibits highly improved dual-functional activity with simultaneous H₂ evolution and selective oxidation of benzyl alcohol. The reaction rate of benzaldehyde and H₂ evolution reaches 125 mmol g_cat⁻¹ h⁻¹ and 159 mmol g_cat⁻¹ h⁻¹, which is the highest efficiency achieved so far for simultaneous coproduction of H₂ fuel and organic chemicals on ReS₂-based composites. This work enriches the application of ReS₂-modified composites in a dual-functional photoredox system and also gives insight into the role of defects in electronic structure modification and activity improvement.