Heterojunction-Type Photocatalytic System Based on Inorganic Halide Perovskite CsPbBr₃^†

The heterojunction-type structure has shown significant merits in tuning the optical properties and carrier physics. Inspired by the excellent absorption capability of halide perovskite materials for visible light, a series of CsPbBr₃/TiO₂ heterojunction-type photocatalysts with various all-inorganic-perovskite/TiO₂ ratios are successfully fabricated by the ligand-assisted reprecipitation (LARP) method. The heterojunction structure extends the light absorption of TiO₂ with good chemical and structural stability. A Pb-O interaction at the CsPbBr₃/TiO₂ interface is observed by the XPS and confirmed by the TRPL showing improved interface carrier transport and stability. The heterojunction-type catalyst shows drastically enhanced photocatalytic activity towards the direct oxidation of toluene with O₂ molecule, as an important reaction for organic chemical synthesis. The optimized sample shows an activity of 2356 μmol·g^–1·h^–1 at 75 °C, 4 times of that of the naked CsPbBr₃ nanocrystals, and 3 times of that of the bare TiO₂. Based on the investigation with trapping agents, a reaction mechanism is hence proposed suggesting that the photo-generated hole may be involved in the rate-limiting step. This work demonstrates the potential of inorganic halide perovskite-based heterojunction structure for photocatalytic applications.