Iron–NitrogenCo-Doped Carbon Nanostructuresfor Applications in Oxygen Reduction Reactions and Microbial FuelCells

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–N_<i>x</i> 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.