A composite of nanoporous carbon and thermally exfoliated graphite as an effective electrode material for supercapacitors

Results are presented of studies on the structure and properties of nanocomposite materials (NCM) based on nanoporous carbon (NPC) and thermally exfoliated graphite (TEG). NCM is promising as electrode material for supercapacitors (SC) with a double electric layer. NPC was obtained from a phytogenic raw material using hydrothermal carbonization. TEG was produced from oxidized natural graphite by thermal exfoliation. A JSM-6490LV (JEOL Ltd., Japan) electron microscope was used to study the samples’ microstructure. A Quantachrome Autosorb instrument was used to study nitrogen adsorption/desorption isotherms and analyse porous structure. The multipoint Brunauer–Emmett–Teller (BET) method was used to determine the specific surface area of electrodes. The electrochemical properties of the samples were analyzed using the methods of galvanostatic cycling and electrochemical impedance spectroscopy employing an AUTOLAB PGSTAT12 (ECO CHEMIE, the Netherlands) measuring instrument. Our study shows that the employment of TEG in this NCM reduces the internal resistance of supercapacitors (SC), and this increases their specific capacitance. The results of electrochemical studies show that the capacitance of SCs based on the noted NCMs amounts to 155–160 F/g. An equivalent circuit is proposed, allowing the simulation of impedance spectra in the frequency range of 10 −3 –10 5 Hz. A physical interpretation of each element of the electric circuit is presented.