Noncovalently functionalized organic graphene aerogel composite for high-performance proton storage

Abstract

Although organic compounds are considered to be promising electrode materials with their remarkable characteristics such as diverse structures, design controllability, and environmental friendliness, their low charge-transfer capability and limited cycling durability hinder their application in aqueous proton batteries. Herein, we prepared a noncovalent phenazine-based graphene aerogel (H/G) composite for aqueous proton storage, which is realized by redox-active Hexaazatrinaphthalene (HATN) organic compound combined with conductive reduced graphene oxide (rGO). The integration of rGO into HATN not only effectively optimizes the electronic structure of the H/G composite to enhance its electrochemical activity, but also the favorable noncovalent π–π interaction existed between HATN and rGO provides a stable structure for fast electron transportation. The obvious electron transfer in the aerogel composite promotes fast and reversible redox reactions occurred with the imino-active HATN in the composite electrode for proton uptake/removal in an aqueous acidic electrolyte, which are demonstrated by in-situ Fourier transform infrared (FTIR) investigation, theoretical calculations and experimental measurements. Therefore, it can deliver a fast, stable and efficient aqueous proton storage behavior with a large specific capacity of 274 mAh g⁻¹ and considerable calendar life with ∼100% capacity retention after 3000 cycles, surpassing previously reported proton-based organic electrodes in aqueous acidic electrolytes. Furthermore, an outstanding soft-package aqueous proton (APB) has been fabricated with considerable long-term cycling stability.