Influence of Porous and Electronic Structure of Carbon Materials on the Supercapacitor Capacitance

I. Borduna, b, Z. Kohuta, b, E. Szymczykiewicza, M. Malovanyyb, N. Nahurskyib, N. Pokladokb aCzestochowa University of Technology, J.H. Dąbrowskiego 42-201 Częstochowa, Poland bLviv Polytechnic National University, S. Bandera 12, 79013 Lviv, Ukraine

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The article discusses the relationship between the porous and electronic structure of nanoporous biocarbon materials and their electrochemical behavior in an alkaline electrolyte. Based on the results of X-ray diffraction and adsorption-desorption gas porometry, it was found that the synthesis temperature of the carbon material affects both the content of the graphite phase and the parameters of the carbon porous structure. The impedance behavior of supercapacitor electrodes made of synthesized carbons at different bias voltages is analyzed. For the obtained Nyquist diagrams, equivalent electrical circuits are constructed based on the modified de Levie model. The influence of the synthesis temperature on the position of the Fermi level is determined by the nature of the change of the minimum in the volt-farad dependence of the spatial charge region capacitance. It has been shown that the shift of the Fermi level to the energy region with a high density of delocalized electron states helps unlock the Helmholtz layer's capacity and, as a result, the specific capacitance of the carbon material increases.

DOI:10.12693/APhysPolA.147.241 topics: supercapacitor (SC), carbon, specific capacitance, Nyquist diagram