Water-stable Bi-based perovskite for efficient photocatalytic hydrogen evolution in aqueous media

Perovskites have attracted considerable interest as potential photocatalysts for sustainable hydrogen generation. Nonetheless, their intrinsic instability in aqueous media significantly constrains their practical deployment in photocatalytic hydrogen evolution. To address this challenge, we propose a versatile strategy for stabilizing Cs₃Bi₂Br₉ (CBB) perovskite photocatalysts through combining zwitterionic ligand encapsulation with Sn⁴⁺ doping. The zwitterionic ligand, synthesized by reacting 4-bromobutyric acid (BBA) with oleylamine (OLA), was employed to passivate the perovskite surface by anchoring to both Bi³⁺ and Br^- sites, effectively mitigating surface defects. Notably, Sn⁴⁺ doping is essential for aqueous stability, as the incorporation of Sn⁴⁺ not only enhances the intrinsic stability of CBB but also reinforces the binding affinity of surface ligands. As a result, the Sn⁴⁺-doped CBB (CBBS_x) with ligand encapsulation demonstrates remarkable stability, retaining its structural integrity in water for over six months and withstanding more than three cycles of photocatalytic testing. Importantly, this strategy demonstrates considerable generality, as it can be readily extended to the synthesis of other halide perovskites. Specifically, the MoS_x-loaded Sn⁴⁺:Cs₃Bi₂Br_xI_9-x (MoS_x/CBBIS_0.2) composite achieves a remarkable hydrogen evolution rate of 18.2 mmol h^-1 g^-1, which represents the highest performance reported to date among Bi-based perovskite photocatalysts.