Kinetically favorable edge-type iron–cobalt atomic pair sites synthesized via a silica xerogel approach for efficient bifunctional oxygen electrocatalysis

Abstract

Efficient fabrication of bimetallic single-atom catalysts (SACs) with bifunctional activity to accelerate both the electrochemical oxygen reduction (ORR) and evolution reactions (OER) is highly desired for advanced battery devices. The chemical environment surrounding the active sites plays a crucial role in modulating charge transfer in catalysis. Herein, we present an in situ silica xerogel tactic to prepare a bifunctional Fe,Co-NC SAC with unique porosity and abundant FeCoN₆ model sites for efficient ORR/OER catalysis. Electrochemical testing of this SAC reveals a potential gap of 0.748 V for the OER and ORR, surpassing the conventional Pt/IrO₂ benchmark. Density functional theory calculations reveal that the edge-type FeCoN₆ site structure greatly reduces the free-energy barrier to promote ORR/OER kinetics. A zinc–air battery using the Fe,Co-NC catalyst exhibits a commendable peak power density of 222 mW cm⁻² and long-term stability (>200 h). This work offers a robust method for synthesizing high-performance bifunctional SACs with kinetically favorable micro-chemical environments.