Living Fe mineral@bacteria encrustation-derived and self-templated preparation of a mesoporous Fe-N-C electrocatalyst with high activity for oxygen reduction

Bacteria-based biomass is a renewable and sustainable precursor for the synthesis of functional carbon, but tailoring its micro-architecture with favorable features usually relies on the use of external activating/graphitizing chemicals and silica templates. Here, we report that bacteria grown with Fe minerals can be used for the preparation of mesoporous Fe-N-C electrocatalysts without activation agents or templates. The living Fe mineral@bacteria encrustation-derived carbon pyrolyzed at 800 °C (Fe@BC-800) displayed outstanding electrochemical activity for oxygen reduction reaction (ORR) in all-pH media. In alkaline media, the Fe@BC-800 exhibited an onset potential of 1.01 V with a half-wave potential of 0.85 V; both values are more positive than those exhibited by commercial Pt/C catalysts. In neutral and acidic media, these values were slightly negative but still comparable to those obtained from Pt/C catalysts. The physicochemical characterization results indicate that the resulting high surface area, high conductivity, abundance in Fe-N-C, pyridinic N, and graphitic N moieties, and heteroatom doping explained the superior activity. The microbial fuel cell (MFC) equipped with the newly developed Fe@BC-800 cathode achieved a maximum power density of 1926.7 mW m−2, an increase of 134.5% relative to that obtained from the Pt/C cathode, indicating the great potential for application in MFCs.

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