Photodeposited Silver-Driven Phase Engineering of Bismuth-Based Halide Perovskite Enabling Tunable Heterojunctions for Efficient CO₂ Photoreduction

Abstract

Cs₃Bi₂Br₉ has emerged as a competitive lead-free photocatalyst owing to its low toxicity and favorable stability. However, its practical application is still limited by the rapid recombination of photogenerated carriers and a narrow photoresponse range. Herein, we report a facile in situ photodeposition strategy to engineer Cs₃Bi₂Br₉ with controlled silver loadings, enabling the selective construction of S-scheme Cs₃Bi₂Br₉@AgBr and Type I Cs₃Bi₂Br₉@Cs₂AgBiBr₆ heterojunctions. Among these, the optimized S-scheme heterojunction (CBB-Ag₂) delivers a CO yield 4.7 times higher than that of pristine Cs₃Bi₂Br₉, achieving superior CO₂ photoreduction performance. Mechanistic investigations reveal that the built-in electric field within the S-scheme heterojunction establishes efficient interfacial charge transfer channels, effectively suppressing carrier recombination and promoting ^•OH generation, which collectively lower the energy barrier for *COOH formation—the rate-determining step in CO₂-to-CO conversion. This work presents a scalable and phase-controllable strategy for constructing high-performance, lead-free perovskite photocatalysts, offering valuable insights into rational heterojunction design for efficient CO₂ valorization toward carbon neutrality.

Keywords

Cs₃Bi₂Br₉ / heterojunction / Pb-free perovskite / photocatalytic CO₂ reduction / photodeposition

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