Strong support effect induced by MXene for the synthesis of metal sulfides nanosheet arrays with sulfur vacancies towards selective CO2-to-CO photoreduction

Selective CO 2 -to-CO photoreduction is under intensive research and requires photocatalysts with tuned microstructures to accelerate the reaction kinetics. Here, we report CuInS 2 nanosheet arrays with sulfur vacancies (V S ) grown on the two-dimensional (2D) support of Ti 3 C 2 T x MXene for CO 2 -to-CO photoreduction. Our results reveal that the use of Ti 3 C 2 T x induces strong support effect, which causes the hierarchical nanosheet arrays growth of CuInS 2 and simultaneously leads to charge transfer from CuInS 2 to Ti 3 C 2 T x support, resulting in V S formed in CuInS 2 . The strong support effect based on Ti 3 C 2 T x is proven to be applicable to prepare a series of different metal indium sulfide arrays with V S . CuInS 2 nanosheet arrays with V S supported on Ti 3 C 2 T x benefit the photocatalytic selective reduction of CO 2 to CO, manifesting a remarkable over 14.8-fold activity enhancement compared with pure CuInS 2 . The experimental and computational investigations pinpoint that V S of CuInS 2 resulting from the support effect of Ti 3 C 2 T x lowers the barrier of the rate-limiting step of *COOH → *OH + *CO, which is the key to the photoactivity enhancement. This work demonstrates MXene support effects and offers an effective approach to regulate the atomic microstructure of metal sulfides toward enhancing photocatalytic performance.