Bi-functional electrocatalysis through synergetic coupling strategy of atomically dispersed Fe and Co active sites anchored on 3D nitrogen-doped carbon sheets for Zn-air battery

Abstract Single atom catalysts (SACs) with unique structure gain much interest in the field of electrocatalysis and show a broad application prospect in long-life rechargeable Zn-air batteries. However, ingenious design and preparation of bi-metal SACs is still difficult to further enhance the bifunctional electrocatalytic activity. Herein, modified zeolitic imidazolate frameworks (SiO2@Fe-ZIF-8/67) was facilely designed to preparation atomically dispersed Fe and Co doping 3D nitrogen-doped carbon nanosheets (A-FeCo@NCNs). The Fe or Co single atoms are identified to be coordinated with N atoms and form FeN4, CoN4 or N3Fe-CoN3 anchored on 3D defect carbon, which act as reactive sites for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Through synergetic coupling effect, A-FeCo@NCNs exhibits excellent electrochemical performance with ORR/OER potential gap of 0.80 V. Density functional theory (DFT) calculations further indicate the synergistic effect between Fe and Co in A-FeCo@NCNs towards the enhancing ORR activity. The as-prepared catalyst assembled Zn-air battery shows a maximum power density, and superb cycling stability, surpassing that based on commercial Pt/C+IrO2. Results from this study may provide a facile method for precious control of dual-metal single sites doped carbon with highly activity and durability for bifunctional electrocatalysis.