Single-atom Fe-regulated Ni2 dual-atom sites as efficient bifunctional oxygen electrocatalysts for rechargeable zinc–air batteries

A ternary–atom Ni DA /Fe SA OER catalyst with Ni 2 N 6 and FeN 4 sites is constructed. • Fe auxiliary sites induce spin polarization and tune the d-band center of Ni 2 N 6 sites. • Ni DA /Fe SA –N–HCB shows a low OER overpotential of 230 mV at 10 mA cm −2 . • Aqueous and solid–state Zn–air batteries exhibit long-term cycling stability up to 700 h and 200 h respectively. Air–breathing energy conversion systems, particularly rechargeable zinc–air batteries (RZABs), are among the most promising high–efficiency energy storage technologies, whose long–term charge–discharge performance is critically governed by the sluggish cathodic oxygen evolution reaction (OER). Nitrogen–doped carbon–supported nickel–based dual–atom catalysts (Ni–DACs) have shown considerable potential for catalyzing this multi–proton–electron reaction, yet their activity is constrained by the difficulty of precisely tuning the electronic structure to balance the adsorption/desorption of key intermediates (*OH, *O, and *OOH). Herein, isolated Fe single–atoms are introduced as auxiliary centers to regulate adjacent Ni 2 dual–atom sites anchored on a nitrogen–doped hollow carbon bowl substrate (Ni DA /Fe SA –N–HCB), constructing a ternary–atom OER electrocatalyst with optimized electronic configuration. Multidimensional in situ spectroscopic characterizations combined with density functional theory calculations demonstrate that Fe incorporation induces electronic redistribution and spin polarization at Ni 2 sites, shifts the d–band center, and lowers the energy barrier of the rate–determining step by optimizing intermediate adsorption/desorption energetics. Consequently, Ni DA /Fe SA –N–HCB achieves an overpotential of 230 mV at 10 mA cm −2 . When applied as the air cathode catalyst, both aqueous and solid–state RZABs exhibit outstanding cycling stability of 700 and 200 h, respectively, with minimal charge–voltage decay of 0.01 and 0.02  V . This work provides an effective electronic structure engineering strategy for constructing durable and efficient OER catalysts toward practical zinc–air battery systems. This work presents an auxiliary–site engineering strategy that couples single–atom Fe sites with dual–atom Ni 2 centers to induce electron spin polarization and optimize the d–band center of the Ni₂ sites. Benefiting from this Fe–induced electronic structure modulation, the resulting ternary–atom catalyst delivers outstanding oxygen evolution activity and achieves long–term operational stability in both aqueous and solid–state rechargeable zinc–air batteries with negligible voltage decay. Download: Download high-res image (65KB) Download: Download full-size image