Passivating Defects and Constructing Catalytic Sites on CsPbBr₃ with ZnBr₂ for Photocatalytic CO₂ Reduction

In recent years, halide perovskites have attracted considerable attention for photocatalytic CO₂ reduction. However, the presence of surface defects and the lack of specific catalytic sites for CO₂ reduction lead to low photocatalytic performance. In this study, we demonstrate a facile method that post-treats CsPbBr₃ with ZnBr₂ for photocatalytic CO₂ reduction. Our experimental and characterization results show that ZnBr₂ has a dual role: the Br^- ions in ZnBr₂ passivate Br vacancies (V_Br) on the CsPbBr₃ surface, while Zn²⁺ cations act as catalytic sites for CO₂ reduction. The ZnBr₂-CsPbBr₃ achieves a photocatalytic CO evolution rate of 57 μmol g^-1 h^-1, which is nearly three times higher than that of the pristine CsPbBr₃. The enhanced performance over ZnBr₂-CsPbBr₃ is mainly due to the decreased V_Br and lower reaction energy barrier for CO₂ reduction. This work presents an effective method to simultaneously passivate surface defects and introduce catalytic sites, providing useful guidance for the regulation of perovskite photoelectric properties and the design of efficient photocatalysts.