Microenvironment modulation of cobalt single-atom catalysts for boosting both radical oxidation and electron-transfer process in Fenton-like system

Two coordination structures (Co-N4 or Co-N3) of cobalt single-atom catalysts (Co-SACs) were prepared by using the chitosan as starting precursor to evaluate the modulated coordination microenvironment of Co-SACs for organics degradation. The degradation performances for carbamazepine (CBZ) as well as the radical/nonradical pathways in Co-N4/PMS and Co-N3/PMS systems was evaluated. Results showed that more radicals could be produced by the Co-N3 catalyst via stronger PMS adsorption as well as the subsequent peroxide bond cleavage of PMS. In addition, a lower energy gap between the CBZ and Co-N3/PMS complex was endowed for the Co-N3 coordination to boost stronger electron-transfer process for CBZ. As a result, both radical and electron-transfer process was boosted by the coordinated Co-N3 sites than those of Co-N4 coordination. This work provides a new insight on the versatile catalytic pathways with modulated coordination microenvironment of carbon-based SACs for high-efficiency PMS activation.