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

Abstract

It remains a great challenge to develop alternative electrocatalysts with high stability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a bifunctional electrocatalyst composed of hollow CoO x (Co 3 O 4 /CoO) nanoparticles embedded in lamellar carbon nanofibers is derived from a Co 2+ -anchored covalent−organic framework. The asfabricated electrocatalyst (CoO x @NC-800) exhibits a half-wave potential (E 1/2 ) of 0.89 V with ultrahigh long-term stability (100% current retention after 3000 CV cycles). Together with promising OER performance, the CoO x @NC-800 based reversible Zn−air battery displays a small potential gap (0.70 V), superior to that of the commercial 20% Pt/C + RuO 2 . The density functional theory (DFT) calculations reveal that the remarkable electrocatalytic performance and stability of CoO x @NC-800 are attributed to the optimized adsorption of the *OOH intermediate and reduced free energy of the potential-limiting step. This study establishes the functionalization of COF structure for fabrication of high-performance carbon-based electrocatalysts.

In-Situ Nanoarchitectonics of Fe/Co LDH over Cobalt-Enriched N-Doped Carbon Cookies as Facile Oxygen Redox Electrocatalysts for High-Rate Rechargeable Zinc–Air Batteries

“…For example, Kuang et al reported a bimetallic Co− Cu−Co-decorated carbon nanosheet for the zinc−air battery with an OCV of 1.424 V, a peak power density of 104.3 mW/ cm 2 , and a specific capacity of 771.7 mAh/g Zn with a voltage gap of 0.85 V when cycled at 10 mA/cm 2 . 65 Similarly, Li et al claimed a Co 2+ -anchored covalent−organic framework-based battery with an OCV of 1.46 V and long cycling for a period of 200 h at 10 mA/cm 2 but with a higher voltage gap of 0.87 V. 66 Though Gopalakrishnan et al reported a longer cycling performance of 370 h for CoS/Co−N x /CoNi/NiS catalystbased batteries, their corresponding voltage gap was reported to be higher (0.96 V). 67 Li et al attempted to alloy Co species into ordered and interconnected macroporous carbon polyhedra and utilize them as a cathode for a rechargeable zinc−air battery with a very low potential gap of 0.6 V, but the charge−discharge operation was carried out at a very low current density of 2 mA/cm 2 .…”

“…For example, Kuang et al reported a bimetallic Co–Cu–Co-decorated carbon nanosheet for the zinc–air battery with an OCV of 1.424 V, a peak power density of 104.3 mW/cm 2 , and a specific capacity of 771.7 mAh/g Zn with a voltage gap of 0.85 V when cycled at 10 mA/cm 2 . Similarly, Li et al claimed a Co 2+ -anchored covalent–organic framework-based battery with an OCV of 1.46 V and long cycling for a period of 200 h at 10 mA/cm 2 but with a higher voltage gap of 0.87 V . Though Gopalakrishnan et al reported a longer cycling performance of 370 h for CoS/Co–N x /CoNi/NiS catalyst-based batteries, their corresponding voltage gap was reported to be higher (0.96 V) .…”