Sulfur-Doped Fe-N-C Cathode in Electro-Fenton System to Produce Hydrogen Peroxide and Degrade Azithromycin

Abstract

Electro-Fenton is a promising process for pollutant removal. The production rate of H2O2 electrosynthesis and the accumulation concentration are crucial, but the performance of existing electrocatalysts is insufficient to achieve industry and academia application wishes. Doping electronegative elements into the metallic nitrogen is expected to produce more H2O2 and achieved higher selectivity. Herein, we rationally designed a ZIF-8 derived Fe-N/S-C catalyst with an electronegative Sulfur which exhibited excellent 2e− pathway oxygen reduction reaction (ORR) activity under alkaline conditions and efficiently degraded azithromycin (AZI). We demonstrate ZIF-8 derived pores in the specific-designed Fe-N/S-C structure significantly increase the accessible ORR active site, and the combination of Fe and S-doping in this catalyst creates the optimal three-phase interface pathways for oxygen transport. The results showed that the Fe-N/S-C-3 exhibited excellent H2O2 selectivity (76%) by changing its electronic structure, with 96% removal of AZI at alkaline conditions (pH = 13) within 210 min. Also, a comprehensive analysis of the key factors affecting H2O2 electrosynthesis is presented, considering aspects related to reactions, catalysts, electrodes, and devices. The spin density and coordinated charge redistribution occurred after S-doping has been demonstrated to be significant and practical for developing electro-Fenton technique to remove bio-refractory contaminants.