Physical and Chemical Analysis of Carbonized Sapropelic Coal

Abstract

By comprehensive physical and chemical analysis, the suitability of carbonized sapropelic coal for use in supercapacitor electrodes and as a matrix for nanostructural composites is assessed. IR spectroscopy shows that the surface of the carbon material contains aliphatic and hydroxyl groups, as well as polyene groups. Analysis of nitrogen adsorption–desorption isotherms indicates that micropore structure predominates in the carbonizate: the mean pore diameter is 1.83 nm; the specific surface is 1472 m²/g; the total pore volume is 0.594 cm³/g; and the proportion of mesopore space is 31.7%. In terms of the size distribution of the pores, almost no pores greater than 5–6 nm are present. When the potential is scanned at rates of 1 and 10 mV/s, the electrical capacitance is 537 and 387 F/g, respectively. The results obtained for test cells on the basis of the galvanostatic charging and electrochemical impedance spectroscopy are consistent with data obtained by cyclic voltammetry. The capacitance data for the cells are determined on the basis of simplified equivalent circuits, using ZSimpWin software. Calculated and experimental Nyquist plots for the equivalent circuits are compared, and the Pearson consistency index is determined. There are good prospects for the use of carbonized sapropelic coal for use in supercapacitor electrodes and as a matrix for nanostructural composites.