Facile synthesis of a single-atom cobalt catalyst to enhance peroxymonosulfate oxidation to degrade emerging contaminants by visible-light regulation: From radical pathway to synergistic pathway.

In-situ modulation of the synergistic effect of both radicals and non-radicals is crucial in the activation of peroxymonosulfate (PMS). In this study, we show a layer-structured carbon nitride with anchored cobalt single atoms was facilely synthesized (0.2Co-CN), followed by an investigation of the mechanism and performance in activating PMS for the removal of emerging contaminants (ECs) assisted by visible light. The results indicate that under visible-light excitation, the catalytic system achieved 97.1% degradation of Norfloxacin (NOR) within 60 min, representing a 3.3-fold increase in kinetics compared to conditions without light. Experimental characterization reveals that the anchored single-atom Cobalt is prone to adsorbing and concentrating PMS, thereby favoring the activation; This observation is further supported by density functional theory calculations. The degradation mechanism shifts from a pure radical pathway to a synergistic pathway involving both radical and non-radical, under in-situ light irradiation. This light-assisted modulation significantly increases both the variety and concentration of reactive oxygen species(ROS), leading to effectively enhanced catalytic performance. The catalyst exhibits robust functionality across a broad pH range without metal ion leaching, possesses unmoved interference resistance without compromising efficiency, demonstrates excellent reusability without significant fatigue, and shows applicability to various ECs and diverse real-world water bodies, paving the road to potential industrial level applications.