Direct Partial Transformation of 2D Antimony Oxybromide to Halide Perovskite Heterostructure for Efficient CO2 Photoreduction

The photocatalytic activity of lead-free perovskite heterostructures currently suffers from low efficiency due to the lack of active sites and the inadequate photogenerated carrier separation, the latter of which is hindered by slow charge transfer at the heterostructure interfaces. Herein, a facile strategy is reported for the construction of lead-free halide-perovskite-based heterostructure with swift interfacial charge transfer, achieved through direct partial conversion of 2D antimony oxybromide Sb₄O₅Br₂ to generate Cs₃Sb₂Br₉/Sb₄O₅Br₂ heterostructure. Compared to the traditional electrostatic self-assembly method, this approach endows the Cs₃Sb₂Br₉/Sb₄O₅Br₂ heterostructure with a tightly interconnected interface through in situ partial conversion, significantly accelerating interfacial charge transfer and thereby enhancing the separation efficiency of photogenerated carriers. The cobalt-doped Cs₃Sb₂Br₉/Sb₄O₅Br₂ heterostructure demonstrates a record-high electron consumption rate of 840 µmol g⁻¹ h⁻¹ for photocatalytic CO₂ reduction to CO coupled with H₂O oxidation to O₂, which is over 74- and 16-fold higher than that of individual Sb₄O₅Br₂ and Cs₃Sb₂Br₉, respectively. This work provides an effective strategy for promoting charge separation in photocatalysts to improve the performance of artificial photosynthesis.