Synthesis of Double Trivalent Perovskite Quantum Dots Cs₃BiSbX₉ (X = Cl, Br, I) for Efficient CO₂ Photoreduction Performance

Non‐toxic Bi halides have great potential in the field of CO 2 photoreduction, but strong charge localization limits their charge separation and transfer. In this study, a series of Cs 3 BiSbX 9 (X = Cl, Br, I) perovskite quantum dots (PQDs) are synthesized by antisolvent recrystallization at room temperature, in which Cs 3 BiSbBr 9 PQDs has high selectivity (94.51%) and yield (15.32 µmol g −1 h −1 ) of CO 2 to CO. In situ DRIFTS and theoretical calculations suggest that the surface charge can be tailored by halogen modulation, allowing for the customization of intermediate species. The Bi─Br─Sb symmetric charge distribution induced by the halogen Br promotes the formation of b─HCOO and reduces the reaction energy barrier of the rate‐limiting step, while the weak electronegativity of Cl and the high electronegativity of I leads to m─HCOO and ─COOH production, which are detrimental to CO generation. This work provides new insights into the design of halide alloy perovskites for CO 2 photoreduction.