Magnetically-altered e_g-orbital occupancy to boost the two-electron oxygen reduction electrocatalysis for faster water decontamination

Abstract

Herein, we demonstrate how the magnetic modulation of the e_g-orbital occupancy of Co ions can become a novel approach to enhance the two-electron oxygen reduction reaction (2e^- ORR) for advanced wastewater treatment by electro-Fenton (EF) process. Nickel foam (NF) substrate coated with ZIF67 was prepared and thermally treated to obtain ferromagnetic NF-supported Co/Co₃O₄ cathodes, whose response to a small magnetic field was further evaluated in EF. The results show an increase of 62.3 % increase in H₂O₂ yield and 46.5 % in faradaic efficiency, improving the degradation rate of the antibiotic sulfamerazine from 77.2 % to 92.4 % in 120 min. This enhancement is attributed to improved electron transfer facilitated by the alteration of e_g-orbital occupancy of Co ions caused by spin regulation under the magnetic field, rather than to mass transport effects. Therefore, magnetic modulation of the e_g-orbital occupancy emerges as a promising strategy to boost EF process for more efficient water decontamination.