Hierarchical porous covalent organic framework/graphene aerogel electrode for high-performance supercapacitors

Abstract

Redox-active covalent organic frameworks (COFs) are an emerging class of energy storage materials due to their notably abundant active sites, well-defined channels and highly surface areas. However, their poor electrical conductivity and low electrochemical accessibility to the active sites have severely restricted their practical applications. Here, we demonstrate the fabrication of an anthraquinone-based COFs/graphene composite aerogel (DAAQ-COFs/GA) electrode through electrostatic self-assembly between negatively charged graphene oxide (GO) nanosheets and modified positively charged nanoflower DAAQ-COFs. The obtained freestanding electrode with a 3D crosslinking conductive network efficiently addresses the limitations of sluggish electron transfer and low utilization of the active sites within the organic framework. Owing to the hierarchical porous structure and the rapidly faradaic reactions of redox sites, the electrode exhibits a high specific capacitance of 378 F g⁻¹ at 1 A g⁻¹ and fast kinetics with about 93.4% capacitive contribution at 3 mV s⁻¹. Furthermore, the binder-free DAAQ-COFs/GA and pure graphene aerogel (GA) electrode are assembled into an asymmetric supercapacitor (ASC), showing an energy density up to 30.5 W h kg⁻¹ at a power density of 700 W kg⁻¹. This work demonstrates the great potential of developing high-performance COF-based energy storage devices.