Lead-Free Halide Perovskite Cs₃ Bi₂ _x Sb_2-2 _x I₉ (x ≈ 0.3) Possessing the Photocatalytic Activity for Hydrogen Evolution Comparable to that of (CH₃ NH₃ )PbI₃.

Abstract

Lead-free perovskites Cs₃ Bi₂ _x Sb_2-2 _x I₉ (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 (CH₃ NH₃ )PbI₃ , Cs₃ Bi₂ _x Sb_2-2 _x I₉ has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm^-2 ), powders of Cs₃ Bi_0.6 Sb_1.4 I₉ (100 mg) loaded with Pt nanoparticles show < H₂ evolution rate of 92.6 µmol h^-1 , which greatly exceeds that of (CH₃ NH₃ )PbI₃ powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h^-1 ). The Cs₃ Bi₂ _x Sb_2-2 _x I₉ has a high stability, with no apparent decrease in catalytic activity after five consecutive H₂ evolution experiments. The doping of Sb in Cs₃ Bi₂ _x Sb_2-2 _x I₉ effectively reduces the contribution of Bi³⁺ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs₃ Bi₂ I₉ and Cs₃ Sb₂ I₉ , Cs₃ Bi₂ _x Sb_2-2 _x I₉ has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.