Surface Boronizing Can Weaken the Excitonic Effects of BiOBr Nanosheets for Efficient O₂ Activation and Selective NO Oxidation under Visible Light Irradiation

The photocatalytic O₂ activation for pollutant removal highly depends on the controlled generation of desired reactive oxygen species (ROS). Herein, we demonstrate that the robust excitonic effect of BiOBr nanosheets, which is prototypical for singlet oxygen (¹O₂) production to partially oxidize NO into a more toxic intermediate NO₂, can be weakened by surface boronizing via inducing a staggered band alignment from the surface to the bulk and simultaneously generating more surface oxygen vacancy (V_O). The staggered band alignment destabilizes excitons and facilitates their dissociation into charge carriers, while surface V_O traps electrons and efficiently activates O₂ into a superoxide radical (^•O₂^-) via a one-electron-transfer pathway. Different from ¹O₂, ^•O₂^- enables the complete oxidation of NO into nitrate with high selectivity that is more desirable for safe indoor NO remediation under visible light irradiation. This study provides a facile excitonic effect manipulating method for layered two-dimensional photocatalysts and sheds light on the importance of managing ROS production for efficient pollutant removal.