The production of porous carbon from calcium lignosulfonate without activation process and the capacitive performance

The electrode is the key part of the electrochemical capacitors, so the electrode material is the most important ingredient in determining their properties. In this study, a simple carbonization method has been presented to prepare porous carbons as electrode materials without activation process, in which inexpensive, reproducible calcium lignosulfonate serves as carbon source. The carbon products were characterized by means of thermogravimetric analysis, X-ray diffraction, field emission scanning electron microscopy and BET surface area measurement. It clearly reveals that the carbonization temperature involved has the crucial effect upon the porous structures as well as the resultant capacitive performances. Given the results from cyclic voltammetry and galvanostatic charge–discharge measurements in 6 M KOH aqueous solution, the present carbons possess high specific capacitance and excellent cycle stability. The maximum specific capacitance reaches as much as 182 F g−1 at the current density of 1 mA cm−2, corresponding to a BET surface area of 1362 m2 g−1, and ca. 95% of the capacitance remains even after 1000 charge–discharge cycles. The present carbons are excellent electrodes candidates for high-rate electrochemical capacitors.