Asphaltene-Based Porous Carbon Nanosheet as Electrode for Supercapacitor

Asphaltene with high aromaticity derived from coal direct liquefaction residue is a favorable precursor to prepare new carbon materials because it is easy to polymerize or cross link. Here, asphaltene was used as a carbon precursor for synthesis of porous carbon nanosheets via an in situ sheet-structure-directing agent from urea thermal polymerization. The porous carbon nanosheet with controllable thickness and a graphitized-like ribbon structure was obtained after KOH activation. As supercapacitor electrode materials, the as-prepared porous carbon nanosheets demonstrated a specific capacitance of 282.9 F/g even at 100 A/g in a three-electrode test and 186.7 F/g at 20 A/g in a two-electrode test. The electrolyte was a KOH aqueous solution in both tests; the specific capacitance of the device retained 89.6% after 10,000 cycles showing a good lifetime and durability. The specific capacitance of the device was 135.4 and 119.1F/g at 1 A/g, respectively, in ionic liquid and organic electrolyte; its highest energy density reached 53.5 Wh/kg (at 159.9 W/kg) and 35.9 Wh/kg (at 134.9 W/kg), respectively. The synergism of high specific surface area to volume ratio developed micromesoporous structure, graphitized-like conduction paths, resulting in excellent specific capacitance and outstanding cycle life and rate performance capability of the prepared porous carbon nanosheets as supercapacitor electrodes.