Fabrication of magnetic BiOBr/ZnFe2O4/CuO heterojunction for improving the photocatalytic destruction of malachite green dye under LED irradiation: Dual S-scheme mechanism

Abstract

Constructing superior heterojunction for organic degradation is extremely important but still a big challenge. In this work, a novel magnetic BiOBr/ZnFe2O4/CuO photocatalyst was constructed via a facile hydrothermal approach followed by a co-precipitation method. However, 1D ZnFe2O4 and CuO were uniformly immobilized on the surface of 2D BiOBr nanoplates to develop stable dual S-scheme heterojunction. Significantly, the ternary heterojunction attained optimum photocatalytic properties, in which 98% of malachite green (MG) was destroyed in 90 min. The BiOBr/ZnFe2O4/CuO composite reflected the fastest reaction kinetics of 6.57, 3.78, and 4.31 folds compared to BiOBr, ZnFe2O4, and CuO, respectively. The synergistic action among BiOBr, ZnFe2O4, and CuO exhibited a crucial role in facilitating the charge dissociation in the dual S-scheme route, generating a huge number of reactive species with stronger redox capabilities that can participate in MG elimination. Besides that, the developed heterojunction revealed boosted surface area, which was attributed to the role of BiOBr nanoplates to regulate the deposition of ZnFe2O4 and CuO with lower aggregation effects. Under visible light irradiation, different operational parameters were optimized, such as pH, catalyst loading, and MG concentration. Of note, BiOBr/ZnFe2O4/CuO manifested facile reusability and excellent stability. Dramatically, the scavenger tests indicated significant contributions of •OH, •O2−, h+ in MG destruction over BiOBr/ZnFe2O4/CuO. Finally, the mechanism outcomes clarified that the dual S-scheme system moderates the density of photo-carriers, promoting their migration along suitable pathways.