Pecan shell-derived nitrogen-doped porous carbon as a sustainable metal-free electrocatalyst for the oxygen reduction reaction

Increasing energy demand and rapid environmental deterioration are major challenges of modern times. Proton exchange membrane fuel cells and metal-air batteries are considered as the most promising alternatives. Both technologies rely critically on the oxygen reduction reaction (ORR) at the cathode, and its efficiency determines the overall efficiency of the fuel cell. At present, platinum-based materials are regarded as the benchmark electrocatalysts for ORR due to their high catalytic activity and favorable reaction kinetics. Despite their potential, the high cost and scarcity of platinum-based ORR catalysts remain a challenge for these systems. Biomass-derived carbon materials have attracted considerable attention as one of the viable alternatives explored in recent years due to their renewability, low cost, environmental friendliness, and natural abundance of carbon. In this work, nitrogen-doped carbon derived from pecan shell was synthesized by ZnCl 2 activation and melamine doping at three mass ratios (1:0.125, 1:0.25, 1:0.5) and characterized by SEM, EDS, Raman spectroscopy, BET surface area analysis, XRD, and XPS. ORR activity was evaluated in 0.1 M KOH using cyclic and linear sweep voltammetry. The 1:0.25 melamine-doped sample exhibited the optimal ORR performance, with the major part of the positive onset potential and the highest limiting current density among all three tested catalysts. These results demonstrate the potential of pecan shell as a biomass precursor for metal-free ORR electrocatalysts.