Bioinspired Fe/Ni Bimetallic Species on Carbonized MOF as Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries

Abstract

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 characterizations confirm 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 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 gZn -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.