Rubidium Doped Cs₂AgBiBr₆ Hierarchical Microsphere for Enhanced Photocatalytic CO₂ Reduction

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 CO₂ reduction is largely limited by serious charge recombination and a lack of efficient active sites. In this work, a rubidium (Rb) doped Cs₂AgBiBr₆ (Rb:CABB) hierarchical microsphere is developed for photocatalytic CO₂ 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 CO₂ 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 CO₂ reduction.