Nitrogen-doped porous carbon fiber with enriched Fe₂N sites: Synthesis and application as efficient electrocatalyst for oxygen reduction reaction in microbial fuel cells

Low-cost, stable and highly efficient oxygen reduction reactions (ORR) electrocatalysts are of great significance for microbial fuel cells to break the limit of the air cathode. The expensive noble metal catalysts are easy to be contaminated due to biofouling, which could damage the catalytic activity significantly. Among the reported non-noble metal catalysts, FeCN materials are promising substitutes that have comparable catalytic activity with Pt/C. In this article, a facile process to obtain N-doped porous carbon fibers (NPCF) with abundant Fe₂N moieties from iron based metal organic framework (MOF(Fe)) embedded electrospun fibers has been developed. The fiber structure promotes the in situ conversion of Fe₂N sites in embedded MOF(Fe) during pyrolysis under NH₃ atmosphere. The abundant Fe₂N sites, presence of pyrrolic nitrogen and hierarchical porous structure of obtained Fe₂N/NPCF make it possess excellent electrocatalytic activity to ORR with comparable performance (E_1/2 = 0.8648 V) and superior long term stability to commercial 20 wt% Pt/C. This work expends the toolbox for design of high performance cathodic catalysts for MFCs and also provides original insights in Fe-N active sites construction for FeNC ORR catalysts.