Controlled synthesis of FeNx-CoNx dual active sites interfaced with metallic Co nanoparticles as bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

Efficient bifunctional oxygen electrocatalysts are essential for high-performance rechargeable Zn-air batteries (rZABs). Herein, a porous hollow carbon nanoshell ([email protected]/N/C) in which FeNx and CoNx metal sites are atomically dispersed and interfaced intimately with metallic Co nanoparticles was derived from pyrolysis of polydopamine-coated ZnCo-ZIFs adsorbed with Fe3+; the chemical interactions among different organic and metal species during the polymer-coating process was inverstigated; their role in regulating the size of the Co nanoparticles, the structure of the hollow carbon nanoshell and the formation of the FeNx-CoNx dual active sites was revealed. The [email protected]/N/C showed superior bifunctional oxygen electrocatalytic activity (ΔE = 0.698 V) and mass activity of 6.8 A gcat.−1 at 0.9 V, outperforming the commercial Pt/C/RuO2 catalysts or the Fe/N/C or Co/N/C counterparts. When assembled for rZABs, the [email protected]/N/C cathode displayed a long cycle life of 200 h (Egap of about 1.0 [email protected] mA cm-2).