Lead‐Free Halide Perovskite Cs3Bi2xSb2–2xI9 (x≈ 0.3) Possessing the Photocatalytic Activity for Hydrogen Evolution Comparable to that of (CH3NH3)PbI3

Lead‐free perovskites Cs3Bi2xSb2–2xI9 (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co‐precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead‐based perovskite (CH3NH3)PbI3, Cs3Bi2xSb2–2xI9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm−2), powders of Cs3Bi0.6Sb1.4I9 (100 mg) loaded with Pt nanoparticles show < H2 evolution rate of 92.6 µmol h−1, which greatly exceeds that of (CH3NH3)PbI3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h−1). The Cs3Bi2xSb2–2xI9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H2 evolution experiments. The doping of Sb in Cs3Bi2xSb2–2xI9 effectively reduces the contribution of Bi3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs3Bi2I9 and Cs3Sb2I9, Cs3Bi2xSb2–2xI9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.