Abstract:Exploring alternative cathodic catalysts capable of highly catalytic activity is crucial to the expansion of bioelectrochemical systems. Herein, Fe 3 O 4 @N-mC is developed as a magnetic cathode catalyst for bioelectroreduction of oxygen. The Fe 3 O 4 @N-mC exhibits better electrocatalytic activity, selectivity (four electron transfer pathway), and long-term electrochemical stability in neutral solutions compared to commercial Pt/C catalyst. The microbial fuel cell using Fe 3 O 4 @N-mC

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... generates a power density of 1141 mWm -2 , which is higher than that of using Pt/C (1022 mWm -2 ). Furthermore, the decline of power density is much lower in reactor with Fe 3 O 4 @N-mC (4 %) than with Pt/C (8 %). With Fe 3 O 4 @N-mC, the cell also obtains higher coulombic efficiency (26 %) than that with Pt/C (21.7 %). The outstanding electrocatalytic activity and stability of Fe 3 O 4 @N-mC show its great potential to be a favorable substitute to Pt/C catalysts in microbial electrochemical energy devices. implementations of air-cathode MFCs is the sluggish kinetics of ORR. 6,7 Traditionally, platinum and its alloys can attain the ORR in four-electron pathway by reducing the overpotential, and thereby resulting in high-efficiency energy recovery and power output. Nevertheless, their high capital cost and susceptibility to time-dependent drift compromise their extensive utilization and commercialization. 8-10 Thus, great efforts have been done to explore cost-effective materials that possess comparable catalytic performance to platinum for the ORR in cathode. Non-precious metal catalysts (NPMCs) with distinguish catalytic ORR activity, good stability and popular price have received increasing attention. Among which, nitrogendoped carbon materials are regarded as favorable catalysts because they can promote the O 2 adsorption, increase active sites and improve the surface hydrophobicity, in addition to its high electrical conductivity and oxidation stability. 11 As reported previously, nitrogen species can conduct a four-electron transfer process, which can reduce the O−O bond and could function as the active sites in ORR process. 12 Nevertheless, most of the pure nitrogen-doped catalysts showed less ORR activity than Pt/C catalysts. Thus, it has been further integrated with nonprecious metals (especially, cobalt or iron) to enhance the ORR activity, endurance to poisons, and the durability.