Oxygen vacancies-mediated CuO@N-doped carbon nanocomposites for non-radical-dominated photothermal catalytic degradation of contaminants

Efficient molecular oxygen activation (MOA) is a critical step for most of the environmental catalysis applications for generating reactive oxygen species (ROS), which is often limited by the lack of energy to excite electrons. The emergence of photothermal catalyst provides an opportunity to make effective use of solar energy to energize electrons for boosting activation of molecular oxygen. Herein, CuO nanoparticles wrapped into nitrogen-doped carbon nanocomposites (CuO@NCs) with abundant oxygen vacancies (OVs) were prepared through a facile one-step synthesis using carboxymethyl chitosan hydrogel as a template. The as-obtained CuO@NCs exhibited excellent photothermal catalytic properties under visible-light irradiation to achieve efficient molecular oxygen activation, thus allowing the effective degradation of bisphenol F (BPF) in complex aqueous environments and actual water matrices. Density functional theory (DFT) calculations reveal that both the enhanced properties of OVs for molecular oxygen adsorption and the accelerated properties of graphitic N for electron transfer contribute significantly to the MOA and charge separation efficiency, resulting in a large amount of ROS. Molecular oxygen is converted to superoxide (center dot O-2(-)) and ultimately to singlet oxygen (O-1(2)), which is the dominant ROS responsible for contaminants degradation. Additionally, a photothermal catalytic degradation pathway of BPF was proposed based on the product detection and theoretical calculations. This study provides an effective method for the in-situ fabrication of metal@N-doped carbon nanocomposite photothermal catalysts and elucidates the mechanism of the photothermal catalytic activation of molecular oxygen for contaminants degradation, providing a promising approach for making effective use of solar energy for environmental remediation.

Automated summary

By using carboxymethyl chitosan hydrogel as a template, CuO nanoparticles wrapped into nitrogen-doped carbon nanocomposites (CuO@NCs) with abundant oxygen vacancies (OVs) were synthesized in one step. The obtained CuO@NCs showed excellent photothermal catalytic properties, achieving efficient activation of molecular oxygen under visible-light irradiation and effectively degrading bisphenol F (BPF) in complex aqueous environments and actual water matrices. Density functional theory (DFT) calculations revealed that the enhanced properties of OVs for molecular oxygen adsorption and the accelerated properties of graphitic N for electron transfer contributed significantly to the molecular oxygen activation and charge separation efficiency, resulting in a large amount of reactive oxygen species (ROS) generation.