Efficient Ag/Ag2O‑Doped Cobalt Metallo-Covalent Organic Framework Electrocatalysts for Rechargeable Zinc-Air Battery

We report a simple encapsulation approach for coordinating cobalt ions with a bipyridine group and doping with Ag/Ag2O nanoparticles (NPs) on a novel metallo-covalent organic framework (MCOF) synthesized using 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid and 2,2′-bipyridine-5,5′-diamine as building blocks and cobalt acetate as precursor (denoted as Ag/Ag2O@MCOF­(Co)). The prepared Ag/Ag2O@MCOF­(Co) is composed of irregular nanosheets, which are embedded with large amounts of Ag2O/AgNPs. Compared with MCOF­(Co) and Ag/Ag2O@MCOF, the obtained Ag/Ag2O@MCOF­(Co) catalyst displays superior oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance due to the synergistic effect among Co–O, Co–N, Ag2O, Ag, and the graphene-like nanostructure. The Ag/Ag2O@MCOF­(Co) catalyst demonstrates an impressive half-wave potential of 0.76 V [vs reversible hydrogen electrode (RHE)] and an average kinetic current density of −4.8 mA cm–2 in an alkaline solution toward ORR. As expected, the primary zinc–air battery is developed using Ag/Ag2O@MCOF­(Co) as an air electrode achieved maximum peak power density (170.8 mW cm–2), a specific discharge capacity of 829 mAh g–1, and stable long-term operation for 100 cycles. This work presents feasible and ingenious strategies for providing porous organic frameworks with potential applications to energy storage and conversion.