Bi4O5Br2/COF S-Scheme Heterojunctions for Boosting H2O2 Photoproduction under Air and Pure Water

Photosynthesizing H2O2 by the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR) is a promising green avenue for H2O2 generation but is limited by the charge carrier recombination rate and sluggish reaction kinetics. Herein, the Bi4O5Br2/COF step-scheme (S-scheme) heterojunction (named BIT) is created for the first time by covalent organic frameworks (TTD-COF) and Bi4O5Br2, with an increased charge carrier separation efficiency and H2O2 photosynthetic activity. Under air and pure water, BIT6 exhibits the highest H2O2 production rate of 5221 mu mol g(-1) h(-1), which is 20 and 1.7 times greater than that of the individual Bi4O5Br2 and TTD-COF. Subsequent mechanism analysis reveals that BIT6 photosynthesizes H2O2 through overpowering indirect 2e(-) ORR paths (O-2-O-2( center dot -)-H2O2 and O-2-O-2 (center dot -)-O-2( 1)-H2O2) and weak direct 2e(-) WOR pathways. Moreover, the in situ H2O2 photogeneration process can be accompanied by the degradation of antibiotics. This study offers in-depth insights into the COF-based S-scheme heterojunctions for enhanced H2O2 photoproduction.