2D/2D Heterojunction of BiOBr/BiOI Nanosheets for In Situ H₂O₂ Production and Activation toward Efficient Photocatalytic Wastewater Treatment

The presence of toxic organic pollutants in aquatic environments poses significant threats to human health and global ecosystems. Photocatalysis that enables in situ production and activation of H2O2 presents a promising approach for pollutant removal; however, the processes of H2O2 production and activation potentially compete for active sites and charge carriers on the photocatalyst surface, leading to limited catalytic performance. Herein, a hierarchical 2D/2D heterojunction nanosphere composed of ultrathin BiOBr and BiOI nanosheets (BiOBr/BiOI) is developed by a one-pot microwave-assisted synthesis to achieve in situ H2O2 production and activation for efficient photocatalytic wastewater treatment. Various experimental and characterization results reveal that the BiOBr/BiOI heterojunction facilitates efficient electron transfer from BiOBr to BiOI, enabling the one-step two-electron O-2 reduction for H2O2 production. Moreover, the ultrathin BiOI provides abundant active sites for H2O2 adsorption, promoting in situ H2O2 activation for center dot O-2(-) generation. As a result, the BiOBr/BiOI hybrid exhibits excellent activity for pollutant degradation with an apparent rate constant of 0.141 min(-1), which is 3.8 and 47.3 times that of pristine BiOBr and BiOI, respectively. This work expands the range of the materials suitable for in situ H2O2 production and activation, paving the way toward sustainable environmental remediation using solar energy.