Magnesium Cobaltite Embedded in Corncob-Derived Nitrogen-Doped Carbon as a Cathode Catalyst for Power Generation in Microbial Fuel Cells

Microbial fuel cells (MFCs) have drawn attention among renewable energy devices. High capital cost, poor durability, and slow oxygen reduction reaction (ORR) kinetics are the major hindrances in the commercialization of the technology. In this work, an environmentally benign approach is followed to synthesize a composite of magnesium cobaltite (MgCo2O4) embedded in nitrogen-doped carbon to optimize the performance of MFCs. Detailed characterization confirms the formation of MgCo2O4 nanostructures in the catalyst treated at 700 °C. Electrochemical studies suggest the superior performance of the MgCo2O4/NC-700 catalyst with a peak reduction current of −0.068 mA and a charge transfer resistance (Rct) of 40.5 Ω. The performance of the air cathodes is evaluated using activated sludge as inoculum in the anode chamber in single-chamber MFCs. The power output of MFC with MgCo2O4/NC-700 as an air cathode reaching 873.81 mW m–2 is 59.56 and 216.05% higher than those of MFCs with Pt/C (547.65 mW m–2) and Co/NC-700 (276.48 mW m–2) cathodes, respectively. These findings suggest that substituting magnesium in transition metal–nitrogen–carbon composites could help realize long-term application as air cathodes for power generation and wastewater treatment in MFCs.