Carbon nitride nanotubes anchored with high-density CuN_x sites for efficient degradation of antibiotic contaminants under photo-Fenton process: Performance and mechanism

The low specific surface area, poor porosity, and weak charge transport caused by the disordered morphology of metal-N-site catalysts are the main factors limiting their environmental applications. Therefore, a hollow-nanotube carbon nitride (Cu-HNCN) catalyst with CuN_x sites dispersed in a hollow nanotube-like CN was constructed and used for the degradation of organic pollutants via the photo-Fenton (PF) process. The high specific surface area, rich porosity, and good visible-light trapping capability of the Cu-HNCN nanotubes were identified. The Cu-HNCN/PF system achieved 96.0% degradation efficiency of tetracycline within 50 min and showed efficient degradation of various antibiotic contaminants. Moreover, the short Cu-N bonds contributed to the improved stability and decreased copper leaching in the Cu-HNCN/PF system. Cu-HNCN, with its enhanced photogenerated charge generation, separation, and transport, was the key to the generation of abundant active species and efficient degradation of pollutants. In addition, frontier electron density theory successfully distinguished the roles of different types of active species in the degradation process. This work provides new insights into the development of catalysts with high stability and accelerated electron transfer to enhance the application of the PF process in practical wastewater purification.