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

Photosynthesizing H 2 O 2 by the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR) is a promising green avenue for H 2 O 2 generation but is limited by the charge carrier recombination rate and sluggish reaction kinetics. Herein, the Bi 4 O 5 Br 2 /COF step-scheme (S-scheme) heterojunction (named BIT) is created for the first time by covalent organic frameworks (TTD-COF) and Bi 4 O 5 Br 2, with an increased charge carrier separation efficiency and H 2 O 2 photosynthetic activity. Under air and pure water, BIT6 exhibits the highest H 2 O 2 production rate of 5221 μmol g –1 h –1, which is 20 and 1.7 times greater than that of the individual Bi 4 O 5 Br 2 and TTD-COF. Subsequent mechanism analysis reveals that BIT6 photosynthesizes H 2 O 2 through overpowering indirect 2e – ORR paths (O 2 –O 2 • – –H 2 O 2 and O 2 –O 2 • – –O 2 1 –H 2 O 2 ) and weak direct 2e – WOR pathways. Moreover, the in situ H 2 O 2 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 H 2 O 2 photoproduction.