Acetate-assistant efficient cation-exchange of halide perovskite nanocrystals to boost the photocatalytic CO₂ reduction

The judicious implantation of active metal cations into the surface of semiconductor nanocrystal (NC) through cation-exchange is one of the facile and viable strategies to enhance the activity of catalysts for photocatalytic CO₂ reduction, by shortening the transfer pathway of photogenerated carriers and increasing the active sites simultaneously. However, cation-exchange is hard to achieve for halide perovskite NCs owing to the stable octahedron of [PbX₆]⁴⁻ with strong interaction between halogen and lead. Herein, we report a facile method to overcome this obstacle by replacing partial Br⁻ with acetate (Ac⁻) to generate CsPbBr₃ NC (coded as CsPbBr_3−xAc_x). A small amount of Ac⁻ instead of Br⁻ does not change the crystal structure of halide perovskite. Owing to the weaker interaction between acetate and lead in comparison with bromide, the corresponding octahedron structure containing acetate in CsPbBr_3−xAc_x can be easily opened to realize efficient cation-exchange with Ni²⁺ ions. The resulting high loading amount of Ni²⁺ as active site endows CsPbBr_3−xAc_x with an improved performance for photocatalytic CO₂ reduction under visible light irradiation, exhibiting a significantly increased CO yield of 44.09 μmol·g⁻¹·h⁻¹, which is over 8 and 3 times higher than those of traditional pristine CsPbBr₃ and nickel doped CsPbBr₃ NC, respectively. This work provides a critical solution for the efficient metal doping of low-cost halide perovskite NCs to enhance their photocatalytic activity, promoting their practical applications in the field of photocatalysis.