Power Production and Degradation of Pesticide Wastewater Through Microbial Fuel Cells with the Modified Activated Carbon Air Cathode by Hollow-Carbon and Carbon-Encapsulated Structures

Microbial fuel cell (MFC) can degrade pesticide wastewater and recovery energy simultaneously, and the activated carbon (AC) air cathode has great prospects for practical application. However, insufficient active sites and the limitation of multi-step electron transfer for oxygen reduction reaction (ORR) requires that AC should be modified by highly efficient electrocatalysts. Herein, busing the confinement effect of carbon-encapsulated metal and hollow carbon, we designed a unique ORR catalyst of Fe-Fe₃O₄-NC through utilizing the 2D leaf-like nanoplates of Zn-ZIF-L to load Prussian blue (PB) particles. The volatilization of low-boiled Zn and the catalysis of iron compounds led to the formation of confined walls of hollow carbon shell and carbon-encapsulated Fe/Fe₃O₄ particles on N-doped carbon substrate. Multivalent iron, a large surface area (368.11 m²·g^-1), N doping, a heterojunction interface, and the confinement effect provided all the Fe-Fe₃O₄-NC-modified AC air cathodes with excellent ORR activity. The optimal samples of AC-Fe-Fe₃O₄-NC-3 achieved a peak power density of 1213.8 mW·m^-2, demonstrating a substantial 82.8% increase over that of the bare AC. Furthermore, its efficiency in glyphosate removal reached 80.1%, surpassing the 23.2% of the bare AC. This study offers new ideas in constructing composite confined structures and the as-designed Fe-Fe₃O₄-NC is a promising modification candidate for the commercial adoption of AC air cathodes.