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.