Supercapacitive properties of the alkali metal hydroxides-activated carbons obtained from sucrose

The influence of different hydroxides, applied to activate carbon black, on the electrochemical properties of activated carbon was investigated. The carbon material was prepared by hydrothermal treatment of sucrose and afterwards thermally activated using KOH, NaOH and LiOH. The electrochemical properties of the obtained samples were examined by cyclic voltammetry and electrochemical impedance spectroscopy and correlated to their physicochemical properties. All samples showed characteristic capacitor-like behaviour. The highest specific capacitance was obtained for the KOH-treated sample, while the increase in capacitance follows the sequence of the growth of ionic radius of a metal from an alkali which is used for activation. It was found that the dependence on the type of hydroxide is due to differences in the radii of a metal. The alkalies of larger radii of metal generated make pores wider and consequently the structure of a porous layer become more accessible to the charge transfer of capacitive response.