Synthesis and CO₂ Photoreduction of Lead-Free Cesium Bismuth Halide Perovskite Nanocrystals

The photoreduction of CO₂ into renewable fuels is a promising approach to solve the global energy and environmental crisis. All-inorganic bismuth (Bi) halide perovskite nanocrystals (NCs) have emerged as an appealing photocatalyst for visible-light-driven CO₂ reduction, but they still have low photocatalytic activity. Herein, a set of lead-free and stable Cs₃Bi₂X₉ (X = Cl, Cl_0.5Br_0.5, Br, Br_0.5I_0.5, I) perovskite NCs were explored for the photocatalytic reduction of CO₂ to CO at the gas–solid interface. In all of the recorded perovskite NCs, the as-synthesized Cs₃Bi₂(Br_0.5I_0.5)₉ showed the highest efficiency of CO₂-to-CO conversion producing 54 μmol g^–1 of CO yield under visible-light irradiation for 3 h. The strategy we proposed may bring up new opportunities for an efficient photocatalytic CO₂ reduction of lead-free perovskite NCs.