Insight into a strategy to improve charge carrier migration in lead-free bismuth-based halide perovskite for efficient selective oxidation of thioanisole under visible light

Lead-free halide perovskites have attracted a lot of attention as a new type of photoelectric conversion material in various solar energy-related applications involving photocatalysis. However, the perovskite photocatalysts still face the problem of insufficient performance arising mainly from the weak charge carrier migration currently. Exploring the strategies to promote the carrier separation efficiency maintains an urgent need. Different from the previous surface modification and construction of heterojunction, herein, we report a new lead-free perovskite solid solution of Cs 3 (Bi x Sb 1−x ) 2 Br 9 with tunable band gap prepared via a facile and efficient co-precipitation method. The introduction of Sb atoms in Cs 3 Bi 2 Br 9 has obviously broadened the absorption of visible light, and making it to be a prominent visible-light photocatalyst for the selective oxidation of thioanisole to methyl phenyl sulfoxide in n -hexane. The single-particle PL study proves that the obtained CBSB (Cs 3 (Bi x Sb 1−x ) 2 Br 9 ) solid solution has a longer carrier lifetime than Cs 3 Bi 2 Br 9 (CBB). In-situ ESR spectra demonstrate that O 2 − plays an important role during the oxidization process. The CBSB also has a superb stability, showing no apparent decrease in the catalytic activity in a five-cycle experiment. We believe our work can provide new understanding in promoting carrier lifetime of the lead-free perovskite materials, present a new approach for selective photo-oxidation, and may shed light on other solar energy conversion areas related to halide perovskites.