Dual atom-bridge effect promoting interfacial charge transfer in 2D/2D Cs3Bi2Br9/BiOBr epitaxial heterojunction for efficient photocatalysis

Optimizing the interfacial quality of halide perovskites heterojunction to promote the photogenerated charge separation is of great significance in photocatalytic reactions. However, the delicately regulation of interfacial structure and properties of halide perovskites hybrid is still a big challenge owing to the growth uncontrollability and incompatibility between different constituents. Here we use BiOBr nanosheets as the start-template to in situ epitaxially grow Cs₃Bi₂Br₉ nanosheets by “cosharing” Bi and Br atoms strategy for designing a 2D/2D Cs₃Bi₂Br₉/BiOBr heterojunction. Systematic studies show that the epitaxial heterojunction can optimize the synergistic effect of BiOBr and Cs₃Bi₂Br₉ via the formation of tight-contact interfaces, strong interfacial electronic coupling and charge redistribution, which can not only drive the Z-scheme charge transfer mechanism to greatly promote the spatial separation of electron-hole pairs, but also modulate the interfacial electronic structure to facilitate the adsorption and activation of toluene molecules. The heterojunction exhibited 62.3 and 2.4-fold photoactivity improvement for toluene oxidation to benzaldehyde than parental BiOBr and Cs₃Bi₂Br₉, respectively. This study not only proposed a novel dual atom-bridge protocol to engineer high-quality perovskite heterojunctions, but also uncovered the potential of heterojunction in promoting electron-hole separation as well as the application in photocatalytic organic synthesis.