In situ growth of lead-free halide perovskites into SiO 2 sub-microcapsules toward water-stable photocatalytic CO 2 reduction.

Halide perovskites (HPs) are highly susceptible to heat, light, or moisture and are easily decomposed even in an ambient environment, which greatly hinders their practical applications. Herein, an in situ growth strategy is presented for implanting an inorganic lead-free HP, Cs 2 AgBiBr 6 , into SiO 2 sub-microcapsules to form a Cs 2 AgBiBr 6 @SiO 2 yolk-shell composite. The SiO 2 sub-microcapsule endows Cs 2 AgBiBr 6 with good thermal and light stability, as well as excellent corrosion resistance against polar solvents. Furthermore, when employed as a lead-free perovskite photocatalyst, the composite exhibits a higher visible-light-driven CO 2 -to-CO rate (271.76 μmol g -1 h -1 ) and much better stability than Cs 2 AgBiBr 6 in water. The formation of a Cs 2 AgBiBr 6 /SiO 2 heterostructure using an in situ growth method alleviates water binding on the perovskites, supported by density functional theory calculations, which is the key to an improvement in the stability of the composite. The in situ growth strategy developed here sheds light on the design and development of HP-based materials for applications involving polar solvents.