Engineering Quantum Dots Protective Layer Boosts Long‐term Stability of Photocatalytic CO2‐to‐CH4 Reduction

Abstract Defect engineering is an effective strategy for enhancing photogenerated carriers separation efficiency for the purpose of promoting photocatalytic CO2 reduction to CH4, which can, however, experimentally not be controlled, leading to the presence of excessive defects on the surface of photocatalyst, and thus crystal destruction and poor long‐term operational stability. Herein, a new strategy of engineering CoS quantum dots (QDs) protective layer is explored to decrease defect concentration for enhancing the long‐term operational stability of zinc indium sulfide (ZIS) photocatalyst. Both experimental and theoretical results demonstrate that the CoS QDs regulate the Zn defect concentration of CZvIS (CoS QDs protected ZvIS) photocatalyst, significantly increasing the photocatalytic stability, and exhibiting long‐term stability of over 600 h, which is the best than reported photocatalyst. In addition, the construction of CoS QDs promotes the separation efficiency and transfer kinetics of photogenerated charge carriers, significantly increasing the photocatalytic CO2 reduction to CH4. The as‐made CZvIS exhibits a high mass activity of 133.5 µmol h−1 g−1, which is 3.8‐fold higher than that of ZIS. Overall, this work proposed a new strategy of constructing CoS QDs to enhance the long‐term stability of photocatalysts, which can bring guiding significance for designing photocatalysts with high stability.