Unique Z-scheme carbonized polymer dots/Bi4O5Br2 hybrids for efficiently boosting photocatalytic CO2 reduction

Constructing heterojunctions with matched band semiconductor is regarded as effective strategy to promote high-efficiency photocatalytic CO2 reduction. Herein, 0D/2D direct Z-scheme heterojunction involving carbonized polymer dots and Bi4O5Br2 nanosheets (CPDs/Bi4O5Br2) is designed and fabricated, which effectively facilitate migration and separation efficiency of photogenerated carriers and retain more negative electron reduction potential of CPDs and more positive hole oxidation potential of Bi4O5Br2. Moreover, CPDs promote adsorption of CO2 and intermediate COOH* as well as desorption of product CO. The direct Z-scheme mechanism of CPDs/Bi4O5Br2 is collaboratively confirmed by theory calculation, X-ray photoelectron spectroscopy and time-resolved transient absorption spectroscopy. The 8 wt% CPDs/Bi4O5Br2 exhibits the maximal CO production of 132.42 mu mol h(-1)g(-1) under Xe lamp irradiation, 5.43 fold higher than that of Bi4O5Br2 nanosheets. The CPDs with up-conversion properties can broaden light utilization range, so that composite material also show better CO2 conversion performance when excitation wavelength is greater than 580 nm.