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