Synergistically enhanced iron and zinc bimetallic sites as an advanced ORR electrocatalyst for flow liquid rechargeable Zn-air batteries

N-coordinated transition-metal materials are promising electrocatalysts for various sustainable and efficient electrochemical energy conversion and storage devices. Here we report a simple synthetic route for simultaneously crafting Fe and Zn bimetallic sites on 1D N-doped hollow mesoporous multi-walled carbon nanotubes (denoted as Fe-Zn/N/C/MWCNTs-800). Attributed to the synergistic effect between the Fe-N-x center and Zn-N-x center on the coupled conductive heterostructured carbon matrix with moderate pyridinic-N and graphitic-N species, the Fe-Zn/N/C/MWCNTs-800 catalyst exhibited remarkable ORR activity, favorable long-term stability, and remarkable methanol tolerance in an alkaline electrolyte, comparable to commercial 20 wt% Pt/C. Moreover, the assembled flow liquid rechargeable Zn-air batteries with Fe-Zn/N/C/MWCNTs-800 as a cathode material also exhibited excellent open-circuit voltage, power density, and cycling stability over 180 h. This report provides a general strategy for fabricating Zn-based N-coordinated transition-metal electrocatalysts for catalytic applications.