<p>Nickel–zinc ferrite catalysts were investigated as air-cathode materials for oxygen reduction in microbial fuel cells (MFCs) operating under neutral conditions. Ni²⁺ and Zn²⁺ were dispersed over tetrahedral and octahedral sites in the catalysts’ spinel structure, which was produced using a sol‒gel method. The materials displayed an ORR onset potential of − 0.40&#xa0;V and a cathodic peak at − 0.53&#xa0;V (versus Ag/AgCl) in half-cell measurements carried out in 100&#xa0;mM phosphate buffer solution. Electrochemical impedance spectroscopy revealed a charge transfer resistance of about 250&#xa0;Ω, which is consistent with a peroxide-mediated two-electron pathway. Significantly, a notable improvement in electrocatalytic performance was noted when integrated into air-cathode electrodes for MFCs using various fabrication techniques. With a cathodic current density of 7.34&#xa0;mA·cm⁻² at − 0.74&#xa0;V and a charge transfer resistance of 4.82&#xa0;Ω in an oxygen-saturated electrolyte, the mixing method produced the highest activity among coating, spraying, and mixing techniques. These findings highlight nickel–zinc ferrite as a potentially viable and useful cathode catalyst for microbial fuel cells and show that electrode fabrication and catalyst–carbon integration are critical in converting intrinsic ORR activity into device-level performance.</p> Graphical Abstract <p></p>