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

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 MN4 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 FeN4 is conceptually produced, which induces an optimized d-band center, lowered free energy barrier, and thus superior ORR activity with a half-wave potential (E1/2) 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. This work provides a novel approach to break the symmetry of the FeN4 moieties in Fe-N-C catalysts via vacancy engineering. The electronic distribution asymmetry of the Fe-N-C catalysts presents boosting activity and prominent durability in a universal pH range. This facile and cost-effective approach with scalable production potential demonstrates promising applications in real-world fuel cells and metal-air batteries.image