Fe₄N particles embedded in nitrogen-doped electrospun carbon nanofibers as efficient ORR catalysts for zinc-air battery

The development of efficient, cost-effective catalysts for the oxygen reduction reaction (ORR) is crucial for advancing zinc-air batteries (ZABs). This study presents Fe₄N nanoparticles embedded in N-doped carbon nanofibers (Fe₄N@CNF-NH₃) as a highly efficient ORR catalyst. The Fe₄N@CNF-NH₃ catalyst was synthesized via electrospinning, followed by high-temperature annealing in an NH₃ atmosphere. This electrospinning technique ensured the uniform dispersion of Fe₄N nanoparticles within the carbon nanofibers (CNFs), preventing agglomeration and enhancing the availability of active sites. Structural and morphological analyses confirmed the formation of Fe₄N nanoparticles with a lattice spacing of 0.213 nm, surrounded by graphitic carbon structures that significantly improved the material’s conductivity and stability. Electrochemical tests demonstrated that Fe₄N@CNF-NH₃ exhibited superior ORR activity, with a half-wave potential of 0.904 V, surpassing that of commercial Pt/C catalysts. This enhanced performance is attributed to the synergistic effects of Fe₄N nanoparticles and the conductive carbon framework, which facilitated efficient charge and mass transfer during the ORR process. Density functional theory calculations further revealed that the introduction of CNFs positively shifted the d-band center of Fe atoms, optimizing oxygen intermediate adsorption and lowering energy barriers for ORR. The practical applicability of Fe₄N@CNF-NH₃ was validated through the assembly of both liquid-state and solid-state ZABs, which exhibited excellent cycling stability, high power density, and superior discharge voltage. This study offers a promising strategy for developing highly active, low-cost ORR catalysts and advances the potential for the commercialization of ZABs.