Preparation and capacitive performance of mesoporous carbon with short time CO₂ activation

The porous carbon material was prepared from sawdust impregnated with a 0.1M FeCl₃ aqueous solution with CO₂ activation at 800°C. Pores were found to develop with increasing activation time. The BET surface area, average pore diameter and volume of the mesopores also became greater with increasing activation time. The ratio of the mesopore to total pore volume in the activated carbon was more than 90% after 5 min of activation. Precise control of the pore size distribution is possible by finely tuning the activation time. The porous carbonized material was examined for use in electric double layer capacitor (EDLC) electrodes. The charge and discharge characteristics of EDLC electrodes using these carbonized materials were studied. Cyclic voltammetry and rate performance indicated good correlation between the pore structure of the carbonaceous materials and the magnitude of the electrolyte. These relationships were in good agreement with the Nyquist plot obtained by measuring the impedance. These results were also in accordance with pore structure analysis obtained using the nitrogen adsorption method. It is suggested that the Nyquist diagram characterizes the pore structure of porous carbon from the viewpoint of ion transfer.