Promotion\nof Single-Electron Transfer by Low-Coordinated\nCo Single Atoms to Facilitate Advanced Oxidation Processes in Wastewater\nTreatment

Heterogeneous catalysts are fascinating for advanced\noxidation\nprocesses (AOPs) in wastewater treatment to reduce cost, metal contamination,\nand pH operation limitations. However, they usually encounter low\ncatalytic efficiency because of the difficult single-electron-transfer\n(SET) pathway during AOPs. Herein, an efficient heterogeneous catalyst\nfor AOPs is realized through the rational regulation of N coordination\naround Co single-atom (SA) centers in favor of SET. As guided by calculations,\nlow N coordination enables a high density of electronic states at\nthe Fermi energy level of SA Co to facilitate SET activation of peroxomonosulfate\n(PMS). A special oxide-compounding method is further applied to decrease\nthe N coordination of SA Co on the carbon carriers from common Co<sub>1</sub>–N<sub>3/4</sub> to the desired Co<sub>1</sub>–N<sub>2</sub>. Co<sub>1</sub>–N<sub>2</sub> shows a delightful activity\nfor AOP degradation of various organic pollutants with kinetic rate\nand turnover frequency values up to 0.862 min<sup>–1</sup> and\n389 h<sup>–1</sup>, respectively, greatly outperforming those\nof Co<sub>1</sub>–N<sub>3/4</sub>. It is also superior in a\nwide pH operation range and has strong resistance to environmental\ndisturbances. Detailed mechanistic investigations confirm the generation\nof singlet oxygen (<sup>1</sup>O<sub>2</sub>) instead of common radical\nO species from the SET between PMS and Co<sub>1</sub>–N<sub>2</sub>, corroborating the calculated results and accounting for\nthe enhanced AOP activity.