Mechanochemical-Driven Uniformly Dispersed Monatomic Fe–N_x Coordination in Carbon for Facilitating Efficient Oxygen Reduction Reaction

Abstract

The need for highly efficient and economical non-Pt electrocatalysts for facilitating the oxygen reduction reaction (ORR) has led to the development of atomically dispersed transition-metal- and nitrogen-doped carbon electrocatalysts. However, this task remains challenging due to the metal components' easy aggregation. The present work addresses this issue by presenting a viable mechanochemical strategy for synthesizing highly dispersed monatomic Fe-Nx coordination in carbon (MFe-NC) electrocatalysts using Fe-zeolitic imidazolate framework precursors. Benefiting from the high density of Fe-Nx coordination, the as-synthesized MFe-NC catalyst exhibits remarkable electrochemical performance toward ORR with greater activity, selectivity, and durability than the commercial Pt/C electrocatalyst. Applying MFe-NC as the catalyst for a Zn-air battery cathode, a high peak power density of 302 mW cm-2 has been achieved. The specific mechanism facilitating the ORR process is unveiled by density functional theory calculations: the favoring of monatomic Fe-N4 sites for the adsorption of intermediate species during the reaction contributes mainly to the high ORR activity.