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

Abstract Lead‐free perovskites Cs 3 Bi 2 x Sb 2–2 x I 9 ( 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 (CH 3 NH 3 )PbI 3 , Cs 3 Bi 2 x Sb 2–2 x I 9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm −2 ), powders of Cs 3 Bi 0.6 Sb 1.4 I 9 (100 mg) loaded with Pt nanoparticles show < H 2 evolution rate of 92.6 µ mol h −1 , which greatly exceeds that of (CH 3 NH 3 )PbI 3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µ mol h −1 ). The Cs 3 Bi 2 x Sb 2–2 x I 9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H 2 evolution experiments. The doping of Sb in Cs 3 Bi 2 x Sb 2–2 x I 9 effectively reduces the contribution of Bi 3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs 3 Bi 2 I 9 and Cs 3 Sb 2 I 9 , Cs 3 Bi 2 x Sb 2–2 x I 9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.