Hollow Bilayer Nanoarchitectonics of ZIF8 Bifunctional Oxygen Electrocatalysts with a CoFe Alloy and Fe/Co–N X Synergy for Rechargeable Zinc–Air Batteries

To expand the application of zinc-air batteries (ZABs) and improve their efficiency, the development of highly active bifunctional oxygen electrocatalysts is of significant practical importance. An efficient bifunctional oxygen electrocatalyst (Fe/dZ8@Co/PDA) for the ORR/OER reaction is successfully prepared by an epitaxial growth method and a modulated bilayer ZIF8 strategy. Compared with the conventional catalyst with a monolayer ZIF8 structure, Fe/dZ8@Co/PDA contains an additional nitrogen source, forming and exposing more active centers. The Fe/dZ8@Co/PDA catalyst exhibits a half-wave potential of 0.85 V and an overpotential of 1.57 V under alkaline conditions. This high catalytic activity is attributed to the synergistic effect between the CoFe alloy and the M-N_X active sites. Additionally, excellent methanol resistance and cycling stability are demonstrated. A high power density of up to 136.6 mW cm^-2 and a specific capacity of 775.6 mA h gZn^-1 were achieved by the assembled ZAB, which also maintained excellent cycling stability for over 170 h. Hierarchical porous hollow bilayer ZIF8-structured bifunctional oxygen electrocatalysts are constructed in this study, providing a new approach for the development of highly active electrocatalysts for the ORR/OER.