Halogen-Engineered Cs2AgBiX6/WS2 Composites With Enhanced Interfacial Dynamics for Efficient Photocatalytic CO2 Reduction.

Metal halide perovskites have exhibited considerable potential for solar-driven photocatalytic CO2 reduction, yet their practical application is largely hindered by lead toxicity and severe charge recombination. In this work, we report the synthesis and screening of lead-free halide double perovskite Cs2AgBiX6 (CABX, X = Cl, Br, I) nanocrystals via an antisolvent technique, followed by the construction of Cs2AgBiX6@WS2 (CABBWS) composites with varying WS2 contents (25, 50, 75 mol%). Structural and interfacial characterizations confirm the intimate contact between CABB particles and WS2 nanosheets, while photophysical and photoelectrochemical (PEC) analyses demonstrate the optimal CABBWS50 with superior charge separation properties. The CABB-WS2 intimate interface enhances charge transport by reducing activation energy, as evidenced by temperature-dependent TRPL measurements. The optimal CABBWS50 achieves a CO evolution rate of 13.65 µmol g- 1 h- 1 under visible-light irradiation (λ > 420 nm), approximately 3.7 times higher than pristine CABB. This work provides comprehensive insights into the design of high-performance lead-free perovskite photocatalysts via rational halogen engineering and interfacial regulation, offering a promising strategy for solar fuel production toward carbon neutrality.