Constructing “π–π” Reinforced Bridge Carbon Nanofibers with Highly Active Co-N/C@pyridine N/C@CNTs Sites as Free-Standing Bifunctional Oxygen Electrodes for Zn–Air Batteries

Abstract

Rechargeable Zn–air batteries (ZABs) have received extensive attention, while their real applications are highly restricted by the slow kinetics of the oxygen reduction and oxygen evolution reactions (ORR/OER). Herein, we report a “bridge” structured flexible self-supporting bifunctional oxygen electrode (CNT@Co-CNF_F50-900) with strong active and stable Co-N/C@pyridine N/C@CNTs reaction centers. Benefiting from the electron distribution optimization and the advantages of hierarchical catalytic design, the CNT@Co-CNF_F50-900 electrode had superior ORR/OER activity with a small potential gap (ΔE) of 0.74 V. Reinforced by highly graphitized carbon and the “π–π” bond, the free-standing CNT@Co-CNF_F50-900 electrode exhibited outstanding catalytic stability with only 36 mV attenuation. Impressively, the CNT@Co-CNF_F50-900-based liquid ZAB showed a high power density of 371 mW cm⁻², a high energy density of 894 Wh kg⁻¹, and a long cycling life of over 130 h. The assembled quasi-solid-state ZAB also demonstrated a high power density, attaining 81 mW cm⁻², with excellent charge–discharge durability beyond 100 h and extremely high flexibility under the multi-angle application. This study provides an effective electrospinning solution for integrating high-efficiency electrocatalysts and electrodes for energy storage and conversion devices.

Graphical Abstract