Synergistic doped and loaded strategies to modify WO3 nanoflowers for efficient photocatalytic degradation of antibiotics through reactive oxygen species regulation

Developing an effective and powerful photocatalyst is important to its practical application in water treatment area, like emerging contaminants removal in water. Herein, through a synergistic strategy of N-doping and carbon quantum dots (CQDs)-loading on WO₃ nanoflowers, CQDs/N-WO₃ was designed, which exhibited excellent photocatalytic performance due to modulated electronic structure. Both experimental characterization and theoretical calculation confirmed that the synergistic effect accelerated the electron transfer ability from O2p to W5d, thus promoting the photogenerated electron and hole separation efficiency owing to the increased W5d orbital electron density. The optimum photocatalyst achieved 100 % removal of gatifloxacin (GAT) with a high reaction rate constant (k₁) of 0.055 min⁻¹ in 60 min under simulated solar light. Moreover, quenching experiment and radical detection demonstrated that the main reactive oxygen species (ROS) changed from ^•OH (WO₃ and N-WO₃) to O₂^•− (CQDs/N-WO₃) for GAT removal. Density functional theory (DFT) calculation based on Fukui index further indicated the reactive sites of GAT were available for electrophilic attack. The internal mechanism was also deduced that after N doped and CQDs loaded on WO₃, narrowed band gap and increased utilization of visible light were observed. Moreover, the high electron density of N sites was more conducive to hole capture, and CQDs enhanced the electron transport as electron acceptor and transporter. The synergistic strategy of doping and loading opens a new perspective for modulating the electronic structure of catalysts, and provides a reference for regulating the ROS types in Fenton-like reactions for the removal of emerging contaminants in water.