Asphaltene-Based Porous Carbon Nanosheet as Electrode\nfor Supercapacitor

Abstract

Asphaltene\nwith high aromaticity derived from coal direct liquefaction\nresidue is a favorable precursor to prepare new carbon materials because\nit is easy to polymerize or cross link. Here, asphaltene was used\nas a carbon precursor for synthesis of porous carbon nanosheets via\nan in situ sheet-structure-directing agent from urea thermal polymerization.\nThe porous carbon nanosheet with controllable thickness and a graphitized-like\nribbon structure was obtained after KOH activation. As supercapacitor\nelectrode materials, the as-prepared porous carbon nanosheets demonstrated\na specific capacitance of 282.9 F/g even at 100 A/g in a three-electrode\ntest and 186.7 F/g at 20 A/g in a two-electrode test. The electrolyte\nwas a KOH aqueous solution in both tests; the specific capacitance\nof the device retained 89.6% after 10,000 cycles showing a good lifetime\nand durability. The specific capacitance of the device was 135.4 and\n119.1F/g at 1 A/g, respectively, in ionic liquid and organic electrolyte;\nits highest energy density reached 53.5 Wh/kg (at 159.9 W/kg) and\n35.9 Wh/kg (at 134.9 W/kg), respectively. The synergism of high specific\nsurface area to volume ratio developed micromesoporous structure,\ngraphitized-like conduction paths, resulting in excellent specific\ncapacitance and outstanding cycle life and rate performance capability\nof the prepared porous carbon nanosheets as supercapacitor electrodes.