Internal electric field driven BiOBr homojunction to accelerate O2 reduction reaction for the photodegradation of tetracycline

Abstract

Oxygen reduction reaction (ORR) in photocatalysis process can generate large quantities of superoxide radicals (•O2–) and hydroxyl radicals (•OH), so as to degrade contaminants efficiently and rapidly. However, the electrons and holes (e-/h+) of single photocatalysts are easy to combine, which limits the ORR efficiency. In this paper, BiOBr microplate (BiOBr-P)/BiOBr nanoflower (BiOBr-F) homojunction with the molar ratio of 1:1 (which was labeled as BPF-1/1) was constructed to enhance the e-/h+ separation and drive the ORR, which can be ascribed to the different work function values between BiOBr-P and BiOBr-F, thereby resulting in the generation of internal electric field (IEF) and band bending. Meanwhile, •O2–, •OH and hydrogen peroxide (H2O2) were analyzed quantitatively, which illustrated that the BPF-1/1 homojunction could accelerate the ORR, producing more •O2– and •OH than BiOBr-P and BiOBr-F. Furthermore, tetracycline (TC) was utilized as the model contaminant to assess the photocatalytic performance of the studied materials. It was proved that BPF-1/1 homojunction displayed the optimum photocatalytic performance compared with BiOBr-P and BiOBr-F. Moreover, the photocatalytic reaction mechanism of BPF-1/1 homojunction photocatalyst for TC degradation was put forward under the visible light. This research offers a feasible strategy for the preparation of effective homojunctions to raise the ORR efficiency and improve the photocatalytic activity.