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 μmol 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 (O2–O2• ––H2O2 and O2–O2• ––O21–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.