Self-template-oriented synthesis of lead-free perovskite Cs3Bi2I9 nanosheets for boosting photocatalysis of CO2 reduction over Z-scheme heterojunction Cs3Bi2I9/CeO2

Lead halide perovskite (LHP) nanocrystals have been intensely studied as photocatalysts for artificial photosynthesis in recent years. However, the toxicity of lead in LHP seriously limits their potential for widespread applications. Herein, we first present the synthesis of 2D lead-free halide perovskite (Cs3Bi2I9) nanosheets with self-template-oriented method, in which BiOI/Bi2O2.7 nanosheets were used as the template and Bi ion source simultaneously. Through facile electrostatic self-assembly strategy, a Z-scheme heterojunction composed of Cs3Bi2I9 nanosheets and CeO2 nanosheets (Cs3Bi2I9/CeO2-3:1) was constructed as photocatalyst for the photo-reduction of CO2 coupled with the oxidation of H2O. Due to the matching energy levels and the close interfacial contact between Cs3Bi2I9 and CeO2 nanosheets, the separation efficiency of the photogenerated carriers in Cs3Bi2I9/CeO2-3:1 composite was significantly improved. Consequently, the environment-friendly halide perovskite heterojunction Cs3Bi2I9/CeO2-3:1 presents impressive photocatalytic activity for the reduction of CO2 to CH4 and CO with an electron consumption yield of 877.04 μmol g−1, which is over 7 and 15 times higher than those of pristine Cs3Bi2I9 and CeO2 nanosheets, exceeding the yield of other reported bismuth-based perovskite for photocatalytic CO2 reduction.