Bioinspired Fe/Ni bimetallic species on carbonized MOF as bifunctional electrocatalysts for rechargeable Zn–air batteries

A bioinspired bimetallic single-atom-based catalyst (Fe/Ni-NC) is generated on N-doped porous carbon derived from ZIF-8 for rechargeable zinc–air batteries (ZABs). Fe and Ni atoms are sequentially introduced into the support networks and stabilized through high-temperature pyrolysis, yielding atomically dispersed Fe–N and Ni–N sites without forming metal nanoparticles. Comprehensive structural characterization confirms the atomic dispersion of Fe and Ni within the carbon matrix. Electrochemical evaluations reveal that Fe/Ni-NC exhibits superior bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance with a low Tafel slope, excellent selectivity for a four-electron ORR pathway, and minimal charge transfer resistance. Density functional theory (DFT) analysis reveals that Ni sites embedded within pyrrolic-N environments (Ni@mPrN) possess optimal O* adsorption energies, serving as the dominant bifunctional active centers responsible for the enhanced oxygen reduction and evolution activities. In ZABs, the catalyst delivers a high open-circuit voltage (1.55 V), peak power density (130.9 mW cm⁻²), and specific capacity (775 mAh g_Zn⁻¹), along with outstanding electrochemical durability. This study highlights the synergistic effect of dual single-atom-based species and porous N-doped carbon in enabling cost-effective, high-performance air cathodes for ZABs.