Oxygen Vacancies-Mediated Cuo@N-Doped Carbon Nanocomposites for Non-Radical-Dominated Photothermal Catalytic Degradation of Contaminants

Abstract

Efficient molecular oxygen activation (MOA) is a critical step for most environmental catalysis to generate reactive oxygen species (ROS), which is often limited by lack of energy to excite electrons. The emergence of photothermal catalyst provides an opportunity to make full 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 by a facile one-step synthesis using carboxymethyl chitosan hydrogel as a template. The as-obtained CuO@NCs exhibit excellent photothermal catalytic properties under visible light irradiation to achieve efficient molecular oxygen activation, thus allowing effective degradation of bisphenol F (BPF) in complex aqueous environments and actual water matrices. The density functional theory (DFT) calculations reveal that both the enhanced properties of OVs for molecular oxygen adsorption and the accelerated properties of graphite N for electron transfer contribute significantly to the MOA and the charge separation efficiency, resulting in a large amount of ROS. Molecular oxygen was converted to superoxide (·O2-) and ultimately to singlet oxygen (1O2 ), which was the dominant ROS responsible for contaminants degradation. In addition, the photothermal catalytic degradation pathway of BPF was proposed according to the product detection and theoretical calculations. This work provides an effective method for the in-situ fabrication of metal@N-doped carbon nanocomposite photothermal catalysts and elucidates the mechanism of photothermal catalytic activation of molecular oxygen for contaminants degradation, providing a promising approach for making full use of solar energy for environmental remediation.

Keywords: Photothermal catalysis, CuO, nitrogen-doped carbon, Oxygen vacancies, Molecular oxygen activation