Highly accessible dual-metal atomic pairs for enhancing oxygen redox reaction in zinc−air batteries

The bifunctional oxygen electrocatalyst acts as a key component for zinc−air batteries; however, the design of economically-feasible bifunctional electrocatalysts showing outstanding functionality and durability remains challenging. Herein, we report the preparation of homogeneously scattered dual Fe−Ni atomic pairs stabilized in porous N-doped carbon matrix with a hierarchically porous nanoarchitecture (denoted as FeNi-NHC), wherein the atomically isolated bimetallic configuration is verified by combinative investigation of microscopy, spectroscopy, and theoretical computations. As an oxygen electrocatalyst in a basic electrolyte, FeNi-NHC exhibits an exceptional activity, achieving an outstanding half-wave potential (0.934 V vs. RHE) for oxygen reduction reaction, and a small overpotential for oxygen evolution reaction (254 mV at 10 mA cm−2). Furthermore, the zinc–air battery constructed with FeNi-NHC catalyst delivers an excellent functionality featuring a high maximum power density (126 mW cm−2) and insignificant activity decay after 200 charge−discharge cycles. Theoretical computations further reveals that the interaction effect of neighboring metal atoms in the bimetallic Fe−Ni sites energetically promotes the catalytic process by reducing the overall reaction barriers via optimization of adsorption−desorption behaviors.