Preparation of chitosan-based porous carbons and their application as electrode materials for supercapacitors

Four porous carbon samples C-600, C-700, C-800, and C-900 were prepared by the carbonization of chitosan at 600, 700, 800, and 900 °C under N and had specific surface areas of 278, 461, 515, and 625 m· g, respectively, based on nitrogen adsorption/desorption measurements. Their electrochemical properties were investigated by cyclic voltammetry (CV) and charge-discharge under constant current. The CV curves of C-800 have a rectangular shape and symmetrical anode and cathode processes. The capacitance of C-600, C-700, C-800, and C-900 are 96, 120, 154, and 28 F· g derived from the galvanostatic charge-discharge curves at a current density of 50 mA· g, respectively. The C-800 composite electrode is highly stable and retains its capacitance well as the capacitance decreased by less than 2% after 1000 cycles at a current density of 1 A· g. Furthermore, with an increase in the concentration of the electrolyte, the shape of the CV curves of the C-800 based electrode becomes more and more rectangular and the specific current also increases. The relationship between the pore structures of the four porous carbon samples and their properties is discussed based on the experimental results. We suggest that chitosan-based porous carbon has potential application as electrochemical capacitor electrode materials.