The development of effective oxygen electrode catalysts for renewable energy technologies such as metal-air batteries and fuel cells remains challenging. Here, we prepared a novel high-performance oxygen reduction reaction (ORR) catalyst comprised of Fe₂N nanoparticles (NPs) in situ decorated over an N-doped porous carbon derived from pomelo peel (i.e., Fe₂N/N-PPC). The decorated Fe₂N NPs provided large quantities of Fe-N-C bonding catalytic sites. The as-obtained Fe₂N/N-PPC showed superior onset and half-wave potentials (0.966 and 0.891 V, respectively) in alkaline media (0.1 M KOH) compared to commercial Pt/C through a direct four-electron reaction pathway. Fe₂N/N-PPC also showed better stability and methanol tolerance than commercial Pt/C. The outstanding ORR performance of Fe₂N/N-PPC was attributed to its high specific surface area and the synergistic effects of Fe₂N NPs. The utilization of agricultural wastes as a precursor makes Fe₂N/N-PPC an ideal non-precious metal catalyst for ORR applications.

The disposal of agricultural wastes such as fresh banana peels (BPs) is an environmental issue. In this work, fresh BPs were successfully transformed into nitrogen-doped carbon nanoparticles (N-CNPs) by using a high shear mixer facilitated crushing method (HSM-FCM) followed by carbonization under Ar atmosphere. Ammonia-activated N-CNPs (N-CNPs-NH₃) were prepared via subsequent ammonia activation treatments at a high temperature. The as-prepared N-CNPs and N-CNPs-NH₃ materials both exhibited high surface areas (above 700 m²/g) and mean particle size of 50 nm. N-CNPs-NH₃ showed a relatively higher content of pyridinic and graphitic N compared to N-CNPs. In alkaline media, N-CNPs-NH₃ showed superior performances as an oxygen reduction reaction (ORR) catalyst (E₀ = −0.033 V, J = 2.4 mA/cm²) compared to N-CNPs (E₀ = 0.07 V, J = 1.8 mA/cm²). In addition, N-CNPs-NH₃ showed greater oxygen reduction stability and superior methanol crossover avoidance than a conventional Pt/C catalyst. This study provides a novel, simple, and scalable approach to valorize biomass wastes by synthesizing highly efficient electrochemical ORR catalysts.