Influence of chemical modification of activated carbon surface on characteristics of supercapacitors

The influence of the change of Fermi level electrons position of activated carbon mu(C) caused by chemical modification of its porous surface by Mn2+ ions on its capacitive characteristics in 7.6 m KOH, 4 m KI, 2 m Znl(2) aqueous solutions is investigated in this work. The detection of adsorbed Mn2+ ions on the surface of activated carbon was carried out according to methods of secondary ionic mass spectrometry (SIMS). An increase in electronic density on the Fermi level of modified with Mn2+ activated carbon was determined with a help of X-ray photoelectron spectroscopy (XPS) data. Capacitive characteristics of the electrodes have been investigated by means of electrochemical impedance spectroscopy, computer modeling, and galvanic discharge. The correlation between electronic structure of modified activated carbon (MAC) and thermodynamic characteristics of ions of the used electrolytes is established. On the basic of the obtained experimental data, electrochemical system of the hybrid capacitor with a specific capacitance of 1740 Fg(-1) and with a specific energy of 30 mWh g(-1) is developed. (C) 2008 Published by Elsevier B.V.