Surface Halogen Compensation on CsPbBr₃ Nanocrystals with SOBr₂ for Photocatalytic CO₂ Reduction

Metal halide perovskite nanocrystals (MHP NCs) have attracted great interest for photocatalytic CO2 reduction. However, monodispersed MHP NCs generally possess a halogen-deficient surface and are capped by labile long-chain organic ligands, exhibiting low charge transfer rates to nearby cocatalysts in photocatalytic systems. Conventional methods of removing the surface ligands easily bring new surface defects, leading to serious charge recombination and low photocatalytic performance. Herein, we demonstrate a facile halogen compensation method to obtain high-quality CsPbBr3 NCs with a Br-filled surface toward photocatalytic CO2 reduction. The use of reactive thionyl bromide (SOBr2) not only promotes the stripping of native ligands but also repairs Br vacancies (VBr) on CsPbBr3 NCs. Such a halogen compensation method facilitates the charge transfer from CsPbBr3 NCs to nearby cocatalysts (e.g., g-C3N4), resulting in a high CO/CH4 production rate of 190 μmol g–1 h–1 in photocatalytic CO2 reduction. This work provides a new strategy to simultaneously enhance the surface properties of photocatalysts and build a favorable interface for their charge transfer, showing great potential in the design and application of perovskites NCs for photocatalytic applications.