Bifunctional magnetic Fe/Fe3O4@Fe-N-C core-shell catalysts for external magnetic field-assisted enhancement of microbial fuel cell performance.

Microbial fuel cells (MFCs) hold significant promise for sustainable energy generation and wastewater treatment. However, their practical performance is often constrained by sluggish cathodic oxygen reduction kinetics and limited anodic bioelectrochemical activity. Although external magnetic fields have been employed to enhance MFC performance, most studies focus on their effect on a single electrode. In this work, we synthesized a core-shell ferromagnetic catalyst, Fe/Fe₃O₄@Fe-N-C, using Fe₃O₄ as the magnetic core and a dopamine-assisted self-polymerization coating strategy. The catalyst exhibits strong magnetic responsiveness and excellent electrocatalytic activity. Under a 140 mT magnetic field, the half-wave potential (E_1/2) of the oxygen reduction reaction (ORR) increases to 0.719 V (vs. 0.705 V without the field), and the kinetic current density at 0.70 V increased by 1.6 times. When applied as both the cathode and anode catalyst in an MFC operating under a bipolar synchronous magnetic field, the system achieves a stable voltage output of 512 ± 14 mV and a maximum power density of 1156.8 ± 38.9 mW m^-2, maintains continuous operation for over 600 h. 16S rDNA sequencing reveals that the magnetic field enriches electroactive bacteria within the anode biofilm, optimizing the microbial community structure. These findings demonstrate that the synergistic integration of magnetic field and ferromagnetic materials can concurrently improve cathodic electrocatalysis and anodic microbial activity, offering a novel strategy for the design of high-performance MFCs.