In situ construction and composition engineering of PbBiO2Br/metal halide perovskite heterojunctions for enhanced interfacial charge transfer and photocatalytic activity.

In situ construction of metal halide perovskite (MHP)-based heterojunctions via atom cosharing has been regarded as an effective strategy to enhance photocatalytic activity, as it establishes high-quality interfaces for rapid charge transfer and separation. Here, the potential of a functional bimetallic self-template for manipulating the composition, structure and consequently the photoelectric properties of atom-cosharing MHP-based heterojunctions was investigated. We employed Sillén-structured bimetallic oxyhalide PbBiO₂Br nanosheets as the self-template to in situ epitaxially grow Pb- and Bi-based or mixed MHP nanocrystals via an acid-etching process. It was revealed that the two "B site" metals, Pb²⁺ and Bi³⁺, enabled the in situ growth of Bi-doped CsPbBr₃ (Bi-CsPbBr₃), CsPb₂Br₅, or Cs₃Bi₂Br₉ nanocrystals on the surface of PbBiO₂Br nanosheets, which could be facilely controlled by tuning the HBr dosage. Therefore, both light absorption and interfacial charge separation of the heterojunction could be facilely tuned simultaneously, which contributed to the manipulation of the corresponding photocatalytic performance. The optimized PbBiO₂Br/Bi-CsPbBr₃ heterojunction exhibited a total electron consumption rate of 31.38 μmol g⁻¹ h⁻¹ when used as the photocatalyst for CO₂ reduction, which was 13.76 times higher than that of the single PbBiO₂Br. Further surface modification by ZIF-67 enhanced the charge separation and CO₂ uptake of the heterojunction, leading to an improved total electron consumption rate of 45.72 μmol g⁻¹ h⁻¹ and enhanced photocatalytic stability. This work provides a simple and effective method for the in situ synthesis of high-quality perovskite heterojunctions, which could be easily extended to other atom-cosharing heterojunctions. [ABSTRACT FROM AUTHOR]