Halogen sites regulation in lead-free AgSb-based perovskites for efficient photocatalytic CO2 reduction

Although the lead-free halide double perovskites (DPs) have shown great promise for the photocatalytic reduction of CO₂, the catalytic performance is still far from satisfactory. In this work, lead-free Cs₂AgSbX₆ (X = Cl, Br, I) DPs nanocrystals (NCs) are prepared by a modified ligand-assisted reprecipitation (LARP) approach at room temperature. The crystal surface, shape, and optoelectronic properties of the AgSb-based DPs are modified using halogen modulation technique. Moreover, a series of Cs₂AgSbX₆ perovskites NCs are utilized as efficient catalysts for the photocatalytic CO₂ reduction. Among them, the Cs₂AgSbBr₆ NCs demonstrate the optimal CO₂ photoreduction activity with CO and CH₄ evolutions of 366 and 49 μmol g⁻¹ respectively under 3h irradiation. Additionally, using the in-situ DRIFTS research, the surface reaction intermediates were precisely identified and dynamically tracked. This study suggests the potential of the lead-free halide DPs NCs as an important platform for the practical solar-to-fuel conversions.