Optimizing electronic synergy of atomically dispersed dual-metal Ni–N4 and Fe–N4 sites with adjacent Fe nanoclusters for high-efficiency oxygen electrocatalysis

Abstract

Single-atom catalysts with M–N₄ configurations have been highly investigated due to their great potential in oxygen electrocatalysis. However, their practical applications in Zn–air batteries are still impeded by the unsatisfied activity and durability. Herein, we develop a dual-metal single-atomic NiFe–N–C catalyst containing Fe nanoclusters by simply pyrolyzing metal phthalocyanine and N-doped carbon precursors. A series of in situ spectroscopic characterizations and density functional theory calculations provide compelling evidence of the co-existence and electronic synergy of Ni–N₄ and Fe–N₄ coordination structures as well as adjacent coupled Fe nanoclusters, which regulate the electronic structure of catalytic active sites and optimize their adsorption/desorption of oxygenated intermediates, accelerating the reaction kinetics and reducing the energy barrier of the oxygen electrocatalysis. As a result, NiFe–N–C exhibits competitive oxygen evolution/reduction reaction (OER/ORR) activity and durability with an ultrasmall ΔE of 0.68 V and a negligible decay of E_1/2 and E_j10 after 50 000 and 90 000 potential cycles, respectively. In addition, Zn–air batteries based on a NiFe–N–C electrocatalyst with a high power density, high specific discharge capacity and ultralong lifespans are realized. This work provides an effective strategy for synergistic electronic modulation of atomically dispersed metal sites, paving a new way for designing advanced bifunctional oxygen electrocatalysts and beyond.