Outstanding capacitive performance of reticular porous carbon/graphene sheets with superhigh surface area

Abstract

Reticular porous carbon/graphene sheets have been successfully synthesized via polymerization of phloroglucinol and formaldehyde on the surface of graphene oxide, followed by activation process using KOH. The chemical structure, physical properties and morphology of samples are characterized systematically by means of scanning electron microscopy, transmission electron microscopy, N2 adsorption, X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy techniques. The results reveal that graphene nanosheet directs the cross-linkage of phenolic novolac resin to form a hierarchical lamellar structure, resulting in its perfect ions transmission channels and high conductivity (1020 S·m−1). The obtained lamellar composite has been exploited as electrode material for supercapacitors in both aqueous electrolyte and ionic liquid electrolyte. This composite exhibits excellent specific capacitance of 270F·g−1 in 30wt% KOH electrolyte at the current density of 1A·g−1. The specific capacitance of this composite can still be maintained to a remarkably high value of 237F·g−1 (87.8% of retention ratio) even at a very high rate of 50A·g−1. In an ionic liquid electrolyte, the highest specific capacitance is evaluated to be 202F·g−1 at 1500mA·g−1 and the energy density of the composite reaches up to a value of 63.2Wh·Kg−1. These figures indicate that such reticular porous carbon/graphene sheets possess a significantly improved electrochemical performance, suggesting their prosperous application in electrochemical energy storage.