Abstract: The electrochemical storage of energy in a special kind of active carbon materials used as capacitor
electrodes was considered. Petroleum coke was used to prepared activated carbons with special porosities and structures by NaOH and vapor etching
with catalysis of NaHCO₃ in turn. Nitrogen adsorption was used to characterize the porous structure of the carbons. Carbon electrodes
were fabricated to serve as electrodes of double layer capacitors. The electrochemical performance of the capacitors in 6M KOH was
investigated with constant current charge and discharge experiments. A specific capacitance larger than 160F/g was achieved with an electrode
composed of 75% active carbon and 20% graphite. Evaluation of capacitor performance by different techniques, e.g. voltammetry, impedance spectroscopy
characteristics was also discussed. A hybrid power source consisting of nickel-hydrogen battery and double layer capacitor was demonstrated to
power successfully simulated power loads encountered in communication equipment or hybrid electric vehicle (HEV).

Key words: supercapacitor, double layer capacitor, active carbon, composite power source