Activated nitrogen-doped carbon nanofibers with hierarchical pore as efficient oxygen reduction reaction catalyst for microbial fuel cells

•Activated N-doped carbon nanofibers have been synthesized via a facile route.•The stack of ANCNFs forms a 3D carbon nanofiber framework with hierarchical pores.•The ANCNFs show better mass transfer and improved performance for ORR.•The ANCNFs exhibit comparable MFC performance to the commercial Pt/C catalyst.

Oxygen reduction reaction (ORR) in microbial fuel cell (MFC) was evaluated by using chemical activated nitrogen-doped carbon nanofibers (ANCNFs) as cathode catalyst. ANCNFs are synthesized through modified oxidative template assembly route and then activated by KOH reagent. The as-prepared ANCNFs formed three-dimensional carbonfiber framework with large specific surface area and hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centered at 0.48, 4.0, 18 and 70 nm. Compared with unactivated nitrogen-doped carbon nanofibers (NCNFs), ANCNFs exhibited a more positive onset potential, higher current density as well as higher electron transfer number in neutral environment, highlighting the importance of chemical activation process for improving the ORR performance. MFCs equipped with ANCNFs catalyst exhibited a high power output of 1377 ± 46 mW m−2, which is about 1.5 times the output of NCNFs cathode (921 ± 29 mW m−2), and as high as nearly 4 times of plain cathode (341 ± 9 mW m−2).

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