Revealing the role of oxygen vacancies in bimetallic PbBiO2Br atomic layers for boosting photocatalytic CO2 conversion

The effect of surface defects on photogenerated carriers separation and CO2 activation is not always clear. Herein, the well-defined bimetallic oxyhalide PbBiO2Br atomic layers with tunable oxygen vacancies (OVs) concentrations have been synthesized and investigated to reveal the role of OVs for photocatalytic CO2 conversion. Ultrafast transient absorption spectroscopy and theoretical calculations revealed that the rich oxygen vacancies (ROV) in PbBiO2Br atomic layers facilitated the transfer of photogenerated electrons from the internal structure to surface and prolonged their lifetime on the surface OVs. PbBiO2Br atomic layers with ROV demonstrated superior CO2 reduction performance with enhanced CO evolution rate of 4.58 mu mol g h(-1) in water under visible light irradiation, which was 2.05 and 10.90 times higher than that of deficient oxygen vacancies (DOV) PbBiO2Br atomic layers and bulk PbBiO2Br, respectively. Intermediate products of CO2 conversion were investigated by in-situ Fourier-transform infrared spectroscopy and the corresponding reaction mechanism was proposed.