Iron–Nitrogen Co-Doped Carbon Nanostructures for Applications in Oxygen Reduction Reactions and Microbial Fuel Cells

Iron–nitrogen codoped carbon (Fe–N–C) nanostructure materials, enhancing catalytic performance by creating active metal center sites, serve as a promising alternative to noble metal catalysts in the oxygen reduction reaction (ORR). In this study, nitrogen-doped carbon dots (NCDs) with an average size of 3.3 ± 0.03 nm and cyanide-functionalized surfaces were utilized to synthesize a nitrogen-doped carbon-dot-modified Fe–N–C nanostructure (NCDM–Fe–N-C). The synthesis leveraged the interactions between cyanide groups on the NCD surfaces and iron ions, resulting in the enrichment of the nanostructure with Fe–Nx reactive species. Under neutral conditions, the optimal NCDM–Fe–N-C-2 sample exhibited significantly enhanced performance compared to conventionally prepared Fe–N–C and commercial 20% Pt/C. The half-wave potential reached 0.75 V vs RHE, and the kinetic current density at 0.70 V stood at 16.4 mA cm–2, surpassing Fe–N–C (0.71 V vs RHE and 4.8 mA cm–2) and 20% Pt/C (0.70 V vs RHE and 3.9 mA cm–2). Furthermore, integrating NCDM–Fe–N-C-2 into microbial fuel cells (MFCs) notably improved the ORR performance at the cathode and enhanced biocompatibility at the anode, resulting in an impressive MFC power density of 959.5 ± 18.6 mW m–2. This study introduces an effective approach to augment ORR activity in Fe–N–C materials and presents a successful concept for advancing MFC development.