Sequential Growth of Cs3Bi2I9/BiVO4 Direct Z-Scheme Heterojunction for Visible-Light-Driven Photocatalytic CO2 Reduction

The high exciton binding energy and lack of a positive oxidation band potential restrict the photocatalytic CO2 reduction efficiency of lead-free Bi-based halide perovskites Cs3Bi2X9 (X = Br, I). In this study, a sequential growth method is presented to prepare a visible-light-driven (lambda > 420 nm) Z-scheme heterojunction photocatalyst composed of BiVO4 nanocrystals decorated on a Cs3Bi2I9 nanosheet for photocatalytic CO2 reduction coupled with water oxidation. The Cs3Bi2I9/BiVO4 Z-scheme heterojunction photocatalyst is stable in the gas-solid photocatalytic CO2 reduction system, demonstrating a high visible-light-driven photocatalytic CO2-to-CO production rate of 17.5 mu mol/(g<middle dot>h), which is approximately three times that of pristine Cs3Bi2I9. The high efficiency of the Cs3Bi2I9/BiVO4 heterojunction was attributed to the improved charge separation in Cs3Bi2I9. Moreover, the Z-scheme charge-transfer pathway preserves the negative reduction potential of Cs3Bi2I9 and the positive oxidation potential of BiVO4. This study offers solid evidence of constructing Z-scheme heterojunctions to improve the photocatalytic performance of lead-free halide perovskites and would inspire more ideas for developing lead-free halide perovskite photocatalysts.