Precise engineering of bimetallic sites via molecular coordination strategy for enhanced bifunctional oxygen...

Dual-atom catalysts show great promise for catalyzing both the oxygen reduction and evolution reactions (ORR and OER). However, the controllable synthesis and precise engineering of their atomic configurations remain challenging. Here, we develop Ni-Fe bimetallic sites with tunable local atomic structure, ranging from isolated FeN₄/NiN₄ dual-atom sites, to a Fe₄ nanocluster-decorated FeN₄/NiN₄ heterostructure (FeN₄-Fe₄-NiN₄), and finally to NiFe alloy nanoparticles, via a dicyandiamide-mediated coordination strategy. The coordination behavior between organic molecules and metal precursors precisely modulates the dispersion of iron and nickel species and their local structure on the porous carbon fiber network. The unique FeN₄-Fe₄-NiN₄ catalyst exhibits remarkable ORR and OER performance, significantly surpassing those of FeN₄/NiN₄, NiFe alloy, and benchmarks Pt/C and RuO₂. Spectroscopic characterizations combined with density functional theory calculations suggest that Fe₄ nanoclusters modulate the local coordination/electronic environment of neighboring FeN₄/NiN₄ sites, optimize *O/*OH adsorption at the rate-determining steps, and thereby accelerate both ORR and OER kinetics. Moreover, a zinc-air battery equipped with FeN₄-Fe₄-NiN₄ as the cathode catalyst demonstrates exceptional cycling stability for over 3300 h. This work offers a general molecular coordination strategy for the precise engineering of local atomic structure in multi-metal catalysts.