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–NX 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.