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Potentiodynamic and galvanostatic investigations of hybrid electrochemical capacitor (HEC) models formed on the base of nanoporous carbon material (NCM) are performed. NCM is obtained from raw materials of plant origin (hemp fire) and modified lithium–manganese spinel Li1.2Mn1.8O4 . The influence of the surface morphology of carbon material on the electric capacity of the HEC is revealed. The total electric capacitance of the HEC models is determined, and its distribution is carried out on the capacitance, which is ensured by the formation of a double electric layer (DEL), and the redox capacitance due to the passage of Faraday reverse reactions. [ABSTRACT FROM AUTHOR]

In this work, the crystal structure of alpha-MnO2 has been obtained by the hydrothermal method. It was determined that the obtained material has a tunnel structure with average particle sizes of 12-15 nm. The electrochemical performances of α-MnO2 in an aqueous solution of 30 % KOH based electrolyte have been investigated by cyclic voltammetry and galvanostatic cycling methods. At the same time, it was determined that the specific capacity of the α-MnO2/electrolyte system decreased from 90 F/g to 55 F/g with an increase of the scan rate from 2 to 10 mV/s. Thus, the maximum values of specific capacitance about 104 F/g were obtained at 0.5 mV/s. The Coulomb efficiency of the electrochemical system is constant and independent of the cycle number under the charge/discharge process. Therefore, the total capacity of the material under investigation can be divided into the capacity of the double electric layer and the diffusioncontrolled redox capacity due to the Faraday reverse redox reactions. It was determined that the contribution of pseudocapacity is 90 % of the total specific capacity. In addition, it has been determined that the α-MnO2/KOH electrochemical system is stable under long-term cycling process. [ABSTRACT FROM AUTHOR]

Chemical activation of nanoporous carbon material with nitric acid, followed by activation in a stream of argon at different temperatures, initiates formation on the surface of the material of amide, pyrrole and pyridine nitrogen compounds that improves the hydrophilic properties and increases its electrical conductivity. Value of the specific capacity of N-enriched carbon material in KOH aqueous solution increases by 30 % and an additional heat treatment in the temperature range of 440-460°C increases it by 10 %. [ABSTRACT FROM AUTHOR]