S-vacancy-assisted fast charge transport and oriented ReS 2 growth in twin crystal Zn x Cd 1- x S: an atomic-level heterostructure for dual-functional photocatalytic conversion.

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 ReS ₂ growth at the S vacancy in twin-crystal Zn _0.5 Cd _0.5 S solid solution ( Sv -ZCS), obtaining an atomic-level heterostructure (ReS ₂ / 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 ReS ₂ 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 ReS ₂ / 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 ReS ₂ / Sv -ZCS composite exhibits highly improved dual-functional activity with simultaneous H ₂ evolution and selective oxidation of benzyl alcohol. The reaction rate of benzaldehyde and H ₂ 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 H ₂ fuel and organic chemicals on ReS ₂ -based composites. This work enriches the application of ReS ₂ -modified composites in a dual-functional photoredox system and also gives insight into the role of defects in electronic structure modification and activity improvement.