Anchored Co–oxo Generated by Cobalt Single Atoms Outperformed Aqueous Species from the Counterparts in Peroxymonosulfate Treatment

How single-atom (SA) materials trigger highly efficient catalysis in peroxymonosulfate (PMS) treatment is not fully understood. In this study, cobalt SA sites were fabricated as a PMS activator for antibiotic degradation and compared with cobalt nanoparticles (NPs). Co-SA/PMS showed superior degradation efficiency, adaptability, and stability to Co-NP/PMS in antibiotic treatment. Identification of the reactive species suggested that Co-SA/PMS were privileged from generating anchored high-valent Co–oxo (Co=O) species for triggering interface oxidation, while Co-NP/PMS generated aqueous radical and non-radical species with less reliability. Theoretical calculations and extended experiments of the oxidation effects showed that Co=O is more stable for Co-SAs than for Co-NPs, providing better accessibility to accomplish interface oxygen transfer. Furthermore, oxidation of different antibiotic contaminants and various typical sulfadoxin degradation pathways were investigated to distinguish the effects of the different pathways. Overall, this study shows the activation improvement caused by different existential forms of cobalt in PMS treatment.