One-Step Rapid Growth of Cs ₂ AgBiBr ₆ /Cs ₃ Bi ₂ Br ₉ /Cs ₂ AgBiBr ₆ Heterojunction Flakes with Enhanced Photocatalytic Ability toward the Photodegradation of Organic Pollutants

Bi-based halide perovskites excel in photocatalysis due to low toxicity and high stability but face challenges like limited photo-generated carrier concentration and separation efficiency. Emerging halide perovskite heterojunctions improve carrier separation, yet their synthesis is complex, and reports regarding pollutant degradation are scarce. Here, we successfully construct and synthesize two-dimensional Cs₂AgBiBr₆/Cs₃Bi₂Br₉/Cs₂AgBiBr₆ (CABB/CBB/CABB) sandwich heterojunction flakes using an antisolvent-mediated one-step rapid crystallization method, which realizes precise control of heterojunction area through stoichiometric ratio engineering. Tetracycline hydrochloride (TC-HCl) degradation under simulated sunlight irradiation is employed to evaluate the photocatalytic performance. Notably, the CABB/CBB/CABB (0.5) heterojunction achieves impressive photodegradation efficiency of 87.9% within 80 min, which is 1.74 and 1.42 times higher than that of CBB and CABB, respectively. The enhanced catalytic activity may be attributed to the synergistic effect of the extended absorption range caused by CABB and its unique twin S-scheme heterojunctions, which facilitate carrier generation and separation. Moreover, the in situ growth of CABB/CBB/CABB heterojunction offers a more efficient carrier separation path, thus achieving high photocatalytic efficiency. The proposed straightforward method for fabricating halide perovskite heterojunctions in this work provides a roadmap for the synthesis of perovskite heterojunctions and paves the way for their applications in high-efficiency photocatalysis and other fields.