Single-atom Co-N5 catalytic sites on carbon nanotubes as peroxymonosulfate activator for sulfamerazine degradation via enhanced electron transfer pathway

[Display omitted] •A novel carbon-based single-atom cobalt catalyst was fabricated by low-temperature solvothermal treatment.•The kobs of Co-N5/CNT was 1.6 times higher than that of the Co-N4/CNT catalyst.•Atomically dispersed Co-N5 sites in the Co-N5/CNT were verified as the active sites.•The electron transfer mechanism was the primary pathway for SMZ degradation in Co-N5/CNT/PMS system. Carbon-based single-atom cobalt catalysts exhibit high catalytic activity for the removal of novel pollutants in advanced oxidation processes. Here, atomically dispersed Co species with five-coordinated nitrogen atoms on carbon nanotubes (CNT) catalyst (Co-N5/CNT) was successfully fabricated via a low-temperature solvothermal reaction. The obtained Co-N5/CNT catalyst exhibited superior catalytic performance for PMS activation for sulfamerazine degradation. Its apparent rate constant kobs was 1.6 times higher than that of the Co-N4/CNT catalyst with four-coordinated nitrogen atoms prepared by the same method. Electron transfer non-radical mechanism was the main pathway for Co-N5/CNT to activate PMS. Higher single-atom cobalt metal loading (1.39 wt% vs 1.08 wt% in Co-N4/CNT) and significantly enhanced electron transfer ability (0.82 e vs 0.77 e in Co-N4/CNT) were the key factors for its superior catalytic performance. This work demonstrates a novel carbon-based single-atom cobalt catalyst for the removal of novel antibiotic contaminants by activating PMS in environmental catalysis applications.