Rubidium Doped Cs 2 AgBiBr 6 Hierarchical Microsphere for Enhanced Photocatalytic CO 2 Reduction

Abstract Halide perovskites have garnered significant attention for their unique optoelectronic properties in solar‐to‐fuel conversions. However, the efficiency of halide perovskites in the field of photocatalytic CO 2 reduction is largely limited by serious charge recombination and a lack of efficient active sites. In this work, a rubidium (Rb) doped Cs 2 AgBiBr 6 (Rb:CABB) hierarchical microsphere is developed for photocatalytic CO 2 reduction. Experimental and theoretical analysis discloses that partially substituting Rb + for Ag + can effectively modulate the electronic structure of CABB, favoring charge separation and making adjacent Bi atoms an electron‐rich active site. Further investigations indicated that Rb doping also reduces the energy barriers of the rate‐determining step in CO 2 reduction. As a result, Rb:CABB demonstrated an enhanced CO yield compared to its undoped counterpart. This work presents a promising approach to optimizing the electronic structures of photocatalysts and paving a new way for exploring halide perovskites for photocatalytic CO 2 reduction.