Phosphorus doping significantly enhanced the catalytic performance of cobalt-single-atom catalyst for peroxymonosulfate activation and contaminants degradation.

Increasing studies have been conducted to explore strategies for enhancing the catalytic performance of metal-doped C-N-based materials (e.g., cobalt (Co)-doped CN) via heteroatomic doping. However, such materials have been rarely doped by phosphorus (P) with the higher electronegativity and coordination capacity. In current study, a novel P and Co co-doped CN (Co-xP-CN) was developed for peroxymonosulfate (PMS) activation and 2,4,4'-trichlorobiphenyl (PCB28) degradation. The PCB28 degradation rate increased by 8.16-19.16 times with Co-xP-CN compared to conventional activators under similar reaction conditions (e.g., PMS concentration). The state-of-the-art techniques, including X-ray absorption spectroscopy and electron paramagnetic resonance etc., were applied to explore the mechanism of P doping for enhancing Co-xP-CN activation. Results showed that P doping induced the formation of Co-P and Co-N-P species, which increased the contents of coordinated Co and improved Co-xP-CN catalytic performance. The Co mainly coordinated with the first shell layer of Co-N, with successful P doping occurring in the second shell layer of Co-N. The P doping favored electron transfer from the C to N atom near Co sites and thus strengthened PMS activation owing to its higher electronegativity. These findings provide new strategy for enhancing the performance of single atom-based catalysts for oxidant activation and environmental remediation.