A heterostructure of halide and oxide double perovskites Cs2AgBiBr6/Sr2FeNbO6 for boosting the charge separation toward high efficient photocatalytic CO2 reduction under visible-light irradiation

Abstract

Halide and oxide double-perovskites (HODPs) are a novel class in semiconductor photocatalysts, which have been deemed as auspicious alternatives to replace the toxic lead-halide perovskites due to their impressive photophysical properties. However, poor charge separation and severe charge recombination have restrained their photocatalytic activities. Described herein is a heterostructure of Cs2AgBiBr6/Sr2FeNbO6 (CABB/SFNO) double perovskites, which is demonstrated for boosting the charge separation efficiency toward efficient photocatalytic CO2 reduction. Comprehensive investigations based on in-situ light-irradiation X-ray photoelectron spectroscopy spectra, electron spin resonance spectra and density functional theory, illustrate that a unique direct Z-scheme electron transfer mode in the CABB/SFNO heterostructure is demonstrated, resulting in a significant spatial charge separation as verified by various characterization techniques including photoelectrochemical measurements, photoluminescence (PL) and time-resolved PL. Consequently, remarkable photocatalytic CO and CH4 production rates of 50.00 and 8.12 µmol g-1h−1, respectively, and a high electron consumption rate of 164.96 µmol g-1h−1, were achieved with visible-light (λ ≥ 420 nm) even without loading any cocatalysts. Representing the highest value among all reported lead-free double perovskite photocatalysts even is comparable with the benchmark CsPbBr3-based Z-scheme. This work certified that HODPs hold great potential for developing efficient and eco-friendly photocatalysts for photocatalytic applications.