Enhanced photocatalytic activity and mechanism insight of copper-modulated lead-free Cs₂AgSbCl₆ double perovskite microcrystals

Lead halide perovskites are prospective candidates for CO₂ photoconversion. Herein, we report copper-doped lead-free Cs₂AgSbCl₆ double perovskite microcrystals (MCs) for gas-solid phase photocatalytic CO₂ reduction. The 0.2Cu@Cs₂AgSbCl₆ double perovskite MCs display unprecedented CO₂ photoreduction capability with CO and CH₄ yields of 412 and 128 μmol g⁻¹, respectively. The ultrafast transient absorption spectroscopy reveals the enhanced separation of photoexcited carriers in copper-doped Cs₂AgSbCl₆ MCs. The active sites and reaction intermediates on the surface of the doped Cs₂AgSbCl₆ are dynamically monitored and precisely unraveled based on the in-situ Fourier transform infrared spectroscopy investigation. In combination with density functional theory calculations, it is revealed that the copper-doped Cs₂AgSbCl₆ MCs facilitate sturdy CO₂ adsorption and activation and strikingly enhance the photocatalytic performance. This work offers an in-depth interpretation of the photocatalytic mechanism of Cs₂AgSbCl₆ doped with copper, which may provide guidance for future design of high-performance photocatalysts for solar fuel production.