Highly Efficient Photocatalytic Hydrogen Evolution by ReS2 via a Two‐Electron Catalytic Reaction

Highly efficient photocatalytic hydrogen evolution (PHE) is highly desirable for addressing the global energy crisis and environmental problems. Although much attention has been given to electron–hole separation, ridding photocatalysts of poor efficiency remains challenging. Here, a two‐electron catalytic reaction is developed by utilizing the distinct trion behavior of ReS2 and the efficient reduction of two H+ (2H+ + 2e− → H2) is realized. Due to the monolayer‐like structure of the catalyst, the free electrons in ReS2 can be captured by the tightly bound excitons to form trions consisting of two electrons and one hole. These trions can migrate to the surface and participate in the two‐electron reaction at the abundant active sites. As expected, such a two‐electron catalytic reaction endows ReS2 with a PHE rate of 13 mmol g−1 h−1 under visible light irradiation. Meanwhile, this reaction allows the typically poor PHE efficiency of pure transition metal dichalcogenides to be overcome. The proposed two‐electron catalytic reaction provides a new approach to the design of photocatalysts for PHE. A two‐electron catalytic reaction is first demonstrated by utilizing the trions in ReS2 and a superior photocatalytic hydrogen evolution rate of 13 mmol g−1 h−1 is achieved, which surpasses the rates of most reported transition metal dichalcogenide composite photocatalysts. This work sheds light on the two‐electron catalytic reaction of photogenerated excitons in semiconductors, providing a new approach to the design of highly efficient photocatalysts.