Tri(Fe/N/F)-doped mesoporous carbons as efficient electrocatalysts for the oxygen reduction reaction

In recent years, advanced designs of non-precious electrocatalysts, such as those with transition metals and heteroatoms into iron‑nitrogen-doped mesoporous carbon, have been actively studied to replace precious-metal electrocatalysts for oxygen reduction reaction (ORR), which are used by future energy storage and conversion devices such as metal-air batteries and fuel cells. In the present study, we propose a noble non-precious electrocatalyst through the introduction of fluorine into iron‑nitrogen doped mesoporous carbon. To this end, we synthesized Tri(Fe/N/F)-doped mesoporous carbon nanofiber (MCNF) using electrospinning, the precursor coating method, and carbonization. Tri(Fe/N/F)-doped MCNFs exhibited an improved onset potential of ~0.9 V, the half-wave potential of ~0.82 V, and limiting-current density of −4.76 mA cm⁻¹, with a four-electron pathway. In addition, Tri(Fe/N/F)-doped MCNFs showed remarkable long-term stability and endurance of methanol-crossover. Therefore, Tri(Fe/N/F)-doped MCNFs exhibited improved ORR performance, which could be explained by the increased specific surface area by mesoporous structures and improved oxygen adsorption by the synergy effects by Fe-N_x macrocycles and a high pyridinic- and pyrrolic-N species resulting from F doping.