Electronic Asymmetry Engineering of Fe–N–C Electrocatalyst via Adjacent Carbon Vacancy for Boosting Oxygen Reduction Reaction

Abstract

Single-atomic transition metal-nitrogen-carbon (M-N-C) structures are promising alternatives toward noble-metal-based catalysts for oxygen reduction reaction (ORR) catalysis involved in sustainable energy devices. The symmetrical electronic density distribution of the M─N₄ moieties, however, leads to unfavorable intermediate adsorption and sluggish kinetics. Herein, a Fe-N-C catalyst with electronic asymmetry induced by one nearest carbon vacancy adjacent to Fe─N₄ is conceptually produced, which induces an optimized d-band center, lowered free energy barrier, and thus superior ORR activity with a half-wave potential (E_1/2 ) of 0.934 V in a challenging acidic solution and 0.901 V in an alkaline solution. When assembled as the cathode of a Zinc-air battery (ZAB), a peak power density of 218 mW cm^-2 and long-term durability up to 200 h are recorded, 1.5 times higher than the noble metal-based Pt/C+RuO₂ catalyst. This work provides a new strategy on developing efficient M-N-C catalysts and offers an opportunity for the real-world application of fuel cells and metal-air batteries.