Low-Potential Iodide Oxidation Enables Dual-Atom CoFe─N─C Catalysts for Ultra-Stable and High-Energy-Efficiency Zn–Air Batteries

The low energy efficiency and limited cycling life of rechargeable Zn–air batteries (ZABs) arising from the sluggish oxygen reduction/evolution reactions (ORR/OERs) severely hinder their commercial deployment. Herein, a zeolitic imidazolate framework (ZIF)-derived strategy associated with subsequent thermal fixing treatment is proposed to fabricate dual-atom CoFe─N─C nanorods (Co₁Fe₁─N─C NRs) containing atomically dispersed bimetallic Co/Fe sites, which can promote the energy efficiency and cyclability of ZABs simultaneously by introducing the low-potential oxidation redox reactions. Compared to the mono-metallic nanorods, Co₁Fe₁─N─C NRs exhibit remarkable ORR performance including a positive half-wave potential of 0.933 V versus reversible hydrogen electrode (RHE) in alkaline electrolyte. Surprisingly, after introducing the potassium iodide (KI) additive, the oxidation overpotential of Co₁Fe₁─N─C NRs to reach 10 mA cm⁻² can be significantly reduced by 395 mV compared to the conventional destructive OER. Theoretical calculations show that the markedly decreased overpotential of iodide oxidation can be ascribed to the synergistic effects of neighboring Co─Fe diatomic sites as the unique adsorption sites. Overall, aqueous ZABs assembled with Co₁Fe₁─N─C NRs and KI as the air–cathode catalyst and electrolyte additive, respectively, can deliver a low charging voltage of 1.76 V and ultralong cycling stability of over 230 h with a high energy efficiency of ≈68%.