An Ultrastable Bifunctional Electrocatalyst Derived from a Co²⁺-Anchored Covalent-Organic Framework for High-Efficiency ORR/OER and Rechargeable Zinc-Air Battery

Itremains a great challenge to develop alternative electrocatalystswith high stability for the oxygen reduction reaction (ORR) and oxygenevolution reaction (OER). Herein, a bifunctional electrocatalyst composedof hollow CoO x (Co3O4/CoO) nanoparticles embedded in lamellar carbon nanofibers is derivedfrom a Co2+-anchored covalent-organic framework.The as-fabricated electrocatalyst (CoO x @NC-800) exhibits a half-wave potential (E (1/2)) of 0.89 V with ultrahigh long-term stability (100% current retentionafter 3000 CV cycles). Together with promising OER performance, theCoO( x )@NC-800 based reversible Zn-airbattery displays a small potential gap (0.70 V), superior to thatof the commercial 20% Pt/C + RuO2. The density functionaltheory (DFT) calculations reveal that the remarkable electrocatalyticperformance and stability of CoO x @NC-800are attributed to the optimized adsorption of the *OOH intermediateand reduced free energy of the potential-limiting step. This studyestablishes the functionalization of COF structure for fabricationof high-performance carbon-based electrocatalysts.