Preparation and Capacitive Properties of Graphite-like Porous Carbon Based on Coal Extracts

Abstract

By using extracts of lignites as carbon precursors, MgO as isolation agent, and KOH as activator, porous graphene-like carbon materials were prepared at 800°C under an inert atmosphere. Porous carbon materials were characterized by FTIR, XRD, TEM and Raman. Further, electrochemical capacitive properties of porous carbons before and after activation as the electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopic techniques. Results indicate that carbon materials after activation exhibit porous film-like shape. The specific surface areas of carbon materials before and after activation are 138.4 m/g and 1396 m/g, respectively. Specific capacitances of carbon materials after activation reach 533 F/g and 390 F/g at 1 A/g and 4 A/g, respectively, while those of carbon materials before activation at same conditions are 366 F/g and 198 F/g. After 8000 cycles at a current density of 5 A/g, the capacitance retentions of carbon materials before and after activation are 72.5% and 40 无 机 材 料 学 报 第 31卷 89.6%, respectively. Accordingly, after KOH activation, the specific capacitance and electrochemical stability of carbon materials are significantly improved. This study verifies that the use of the isolation agent and the activator can obtain highly flexible graphene-like porous carbon with high capacitance performance.