Ordered porous nitrogen-doped carbon with atomically dispersed FeN4 for efficient oxygen reduction reaction in microbial fuel cell

It is necessary to develop cost-effective platinum group materials (PGM)-free cathode catalysts for the oxygen reduction reaction (ORR) to replace the state-of-the-art noble metal for the commercialization of microbial fuel cells (MFCs). Fe-N-C catalysts are one of the promising candidates for commercial Pt/C. Herein, a new cost-effective and highly stable Fe-N-C catalyst was designed and successfully prepared via a facile process. The catalyst was prepared through one single thermal conversion from Fe-doped ZIF-8 (zeolitic imidazolate framework), a metal-organic framework (MOF) containing well-defined FeN4 coordination. The mesopores in the unique structure of MOF promoted efficient mass transfer, while those arising from the pyrolysis of the MOF produced more active sites. Unlike previous preparation methods, post-treatments were avoided here. As a result, the Fe-N-C cathode had a high ORR activity with a half-wave potential (E1/2) of 0.85 V in a 0.1 M KOH aqueous solution. The classic MFC with this cathodic catalyst provided a maximum power density of up to 1508 mW m−2. The Fe-ZIF-8 isprepared by using an ultrasonic nucleation method. The Fe-N-C has abundant atomic FeN4 sites dispersed on porous carbon, served as efficient ORR electrocatalysts for microbial fuel cells. The Fe-N-C-900 catalyst exhibits a high ORR activity with onset potential of 0.91 V in a 0.1 M KOH aqueous solution. Based on the as-prepared Fe-N-C-900 as the air cathode catalyst, a stable microbial fuel cell (MFC) device is fabricated and tested, performing a maximum power density of 1508 mW m−2. [Display omitted] •The Fe-N-C catalyst with atomically dispersed FeN4 was derived from metal-organic framework.•MOF structure facilitated electron transfer and active sites exposure.•Fe-ZIF-8 precursor was prepared by an ultrasonic nucleation method.•The Fe-N-C-900 electrode showed excellent electrocatalytic activities for ORR.•MFCs with Fe-N-C-900 cathode had a maximum power density of 1508 mW m−2.