Interfacial Electrostatic Field Boosted Exciton Dissociation of Phosphorylated BiOBr for Efficient O2 Activation and Chlorobenzene Degradation

Semiconductor-based photocatalytic O2 activation is a facile, green, yet versatile strategy to produce reactive oxygen species (ROS) for environmental remediation and pollution control but suffers from low ROS generation rate. Herein, we demonstrate that a simple surface phosphorylation can greatly enhance the O2 photoactivation of BiOBr to produce superoxide radical (center dot O2-) via boosting exciton dissociation. The phosphorylated BiOBr surface establishes an interfacial electrostatic field from the bulk to the surface, and weakens the surface Bi-O bonds to induce oxygen vacancy (VO) generation simultaneously. This interfacial electrostatic field attenuates the exciton binding energy (Eb) from 266 to 89 meV, facilitating the dissociation of excitons to charge carriers, i.e., electrons and holes. Driven by the interfacial electrostatic field, the photoinduced electrons migrate to and are confined by the surface VO, thus activating absorbed O2 to the superoxide radical (center dot O2-). As a result, surface phosphorylated BiOBr could degrade the synthetic chlorobenzene solution with a 6.3 times higher rate (0.69 h-1) than BiOBr (0.11 h-1) under visible light. Impressively, this surface phosphorylated BiOBr was able to decrease the COD value of industrial chlorobenzene wastewater from 153 to 19 mg/L, below the Water Quality Standards Category III of China. This study sheds light on the design and synthesis of high-performance photocatalysts and also provides a green strategy for wastewater treatment with solar energy.

Automated summary

This study demonstrates that surface phosphorylation can greatly enhance the O2 photoactivation of BiOBr, leading to a higher generation rate of superoxide radicals. The phosphorylated BiOBr surface establishes an interfacial electrostatic field, weakens the surface Bi-O bonds, and induces oxygen vacancy (VO) generation, facilitating exciton dissociation and the activation of absorbed O2. This surface phosphorylated BiOBr shows a significantly higher degradation rate of chlorobenzene solution and is able to decrease the COD value of industrial chlorobenzene wastewater below the water quality standards.