Preparation of porous carbons from cypress using super-heated steam: III. Performance in electric double layer capacitors

Cypress charcoals, which were prepared with different temperatures and transferring rates under a flow of super-heated steam, were used for the electrode of electric double layer capacitor (EDLC) with 1 M H2SO4 electrolyte. EDLC capacitance of cypress charcoals prepared was about 250 F/g with a current density of 20 mA/g, about 160 F/g with 50 mA/g and about 120 F/g with 1000 mA/g. Capacitance observed was shown to be governed by pore structure of cypress charcoal and was tried to explain by the contributions from microporous and external surface areas. Rate performance evaluated from the ratio of the capacitance measured with 1000 mA/g to that with 50 mA/g was relatively high, about 0.7, for cypress charcoals prepared.