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

Single-atom catalysts with M-N-4 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-N-4 and Fe-N-4 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 Delta E 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.