Hierarchically Porous Graphene Aerogels with Abundant Oxygenated Groups for High-Energy-Density Surpercapacitors

Abstract

A hierarchically porous graphene aerogel (HP-GA) with abundant oxygenated groups and hand-tearing bread-like macromorphology is achieved by a sacrificial MnO2 template approach. Oxygenated groups on graphene sheets improve the wettability of HP-GA to an aqueous electrolyte and contribute to pseudocapacitance. The chlorine (Cl2) gas as a result of the reaction of MnO2 and HCl is responsible for the formation of the hierarchically porous microstructure and hand-tearing bread-like macromorphology, ensuring a large electrolyte accessible surface area within the electrodes. When used as the active electrode material in supercapacitors, HP-GA exhibits a large specific capacitance of 284 F g–1 at 1 A g–1 and ultrahigh energy density of 10 Wh kg–1 at 250 W kg–1 in an aqueous electrolyte. This work provides a versitile, simple, and easy to control way to alter the microstructure and macromorphology of graphene-based areogels that have promising applications in many areas, including adsorption, energy storage, heat insulation, acoustical insulation, and intelligent sensing system.