Electrochemical capacitors based on highly porous carbons prepared by KOH activation

Various coal and pitch-derived carbonaceous materials were activated for 5 h at 800 degreesC using potassium hydroxide and 1:4 component ratio. Porosity development of the resultant activated carbons (ACs) was assessed by N-2 sorption at 77 K and their capability of the charge accumulation in electric double layer was determined using galvanostatic, voltammetric and impedance spectroscopy techniques. ACs produced from different precursors are all microporous in character but differ in terms of the total pore volume (from 1.05 to 1.61 cm(3) g(-1)), BET surface area (from 1900 to 3200 m(2) g(-1)) and pore size distribution. Very promising capacitance values, ranging from 200 to 320 Fg(-1), have been found for these materials operating in acidic 1 mol 1(-1) H2SO4 electrolytic solution. The variations in the electrochemical behavior (charge propagation, self-discharge, frequency response) are considered in relation to the porous texture characteristics, elemental composition but also possible effect of structural ordering due to various precursor materials used. Cycling investigation of all the capacitors has been also performed to compare ability of the charge accumulation for different carbon materials during subsequent cycles. (C) 2003 Elsevier Ltd. All rights reserved.