Self-assembled lead-free double perovskite-MXene heterostructure with efficient charge separation for photocatalytic CO2 reduction

Lead-free double perovskites with superior stability have been considered as promising non-toxic substitutes to their lead-contained counterparts in photocatalysis . However, the severe charge recombination greatly restricts their potential as high-performance photocatalysts. Herein, for the first time, we present a self-assembled heterostructure of lead-free double perovskite Cs 2 AgBiBr 6 nanocrystals (NCs) on the surface of MXene nanosheets via mutual electrostatic attraction. The presence of MXene nanosheets effectively promotes the formation of free charge carriers in Cs 2 AgBiBr 6 NCs via reducing the exciton binding energy. Additionally, the ultrafast photogenerated electron transfer from Cs 2 AgBiBr 6 to MXene with a timescale of 1.1 ps largely prolongs the charge carrier lifetime by two times. As a result of the efficient charge separation and electron extraction, the Cs 2 AgBiBr 6 /MXene heterostructures achieve a high photoelectron consumption yield of 50.6 µmol g −1 h −1 for photocatalytic CO 2 reduction, which surpasses most previously reported lead-free perovskite-based catalysts.