Boosting Oxygen Reduction Reaction in Alkaline Media via Fe-Nx-Enriched Carbon Electrocatalysts Derived from Waste Pod Shells

A key challenge in advancing metal–air battery technologies is the development of low-cost oxygen reduction reaction (ORR) electrocatalysts with efficiency approaching that of premium benchmarks Pt/C. Herein, we report the synthesis of a Fe/N-co-doped carbon from a sustainable biomass pod shells, melamine, and iron acetate, employing a facile one-step pyrolysis approach. The optimized catalyst, C-N-Fe-800, exhibits good ORR activity in an alkaline medium, with an onset potential of 0.92 V and a half-wave potential of 0.79 V (vs. reversible hydrogen electrode (RHE)), surpassing the performance of commercial Pt/C in terms of durability and methanol tolerance. Good electrocatalytic performance stems from a synergistic contribution involving multiple active centers and structural merits. The active species Fe-Nx sites directly govern the intrinsic catalytic activity, while the presence of some mesopores, as indicated by the N2 adsorption–desorption isotherms, may aid electrolyte penetration and reactant transport, although the relatively low BET surface area limits the extent of this porosity. This work provides a strategic design principle for developing high-performance, non-precious-metal ORR catalysts from abundant biomass for application in alkaline energy conversion devices.