Identifying the Synergistic Role of Graphitic Nitrogen and Cobalt Nanoparticle in Electron Transfer Pathway Toward Fenton-Like Catalysis.

Cobalt and nitrogen co-doped catalysts have been widely reported in Fenton-like processes for water decontamination. However, there is not yet clear how the interaction between cobalt and nitrogen regulates the non-radical electron transfer mechanism. Here, a carbon nanotube (CNT) catalyst (CoN/C-8) containing nitrogen element and a beads-on-string cobalt nanoparticles (Co NPs) was synthesized to utilize peroxymonosulfate (PMS). The CoN/C-8/PMS process exhibited excellent stability and reusability for water treatment, maintaining above 95% of tetracycline hydrochloride (TCH) removal under a continuous-flow operation of 600 min. A series of electrochemical tests, COMSOL multiphysics simulations, and density functional theory calculations collectively elucidate an electron transfer pathway from TCH to the complex of catalyst and PMS (PMS*) and the synergistic effect of graphitic N (Grap-N) and Co NPs during the CoN/C-8/PMS process. Interestingly, although the total number of electrons from the catalyst to PMS increases after the Grap-N interface covering the Co NPs, the main electron donor shifts from the Co NPs to the Grap-N-containing carbon layer interface. These results suggest that the Grap-N interface as an electron transfer highway could protect the easily deactivated cobalt nanoparticles and effectively enhance the stability and life of the catalyst, thus providing valuable guidance for water decontamination.