Preparation And Capacitance Performance Of Activated Carbon From The Peels Of Carya

Activated carbon with porous structure, widely pore size distribution, hugespecific surface area and stable physical and chemical properties has been used as akind of good adsorption material, which has widely used on environmentalprotection and energy storage. Supercapacitor as a new type of energy storagedevices with high power density, high energy density, fast charge and discharge andlong service life has caused more attention around the world. The important factorsthat affect the supercapacitor electrode materials are the specific surface area, poresize distribution and surface functional groups of activated carbon. Series of highspecific surface area activated carbon were prepared from the Peels of Carya withKOH as the activation agent. The effects of the carbonization and activationparameters were investigated. The surface functional groups and porous structure ofactivated carbon modified with HCl、H2SO4、HNO3、HF had explored. Thecapacitance of supercapacitor assembled with above activated carbon had researched.The main results are as follows:(1) Activated carbons prepared from the Peels of Carya Cathayensis Sarg with KOHas the activation agent were high specific surface area of3025.4m~2/g and porevolume of1.60cm~3/g which obtained at the optimizational conditions ofcarbonization temperature of700℃, carbonization time of1h, KOH/precursor ratioof3, activation temperature of900℃and activation time of1h.(2) The activated carbons modified with H2SO4and HNO3had more carboxyl andhydroxyl groups. However, the activated carbons modified with HF and HCl hadmore carbonyl groups. The yield of modified activated carbons was: AC-HF＜AC-HNO3＜AC-HCl＜AC-H2SO4. The ash content of modified activated carbonswas: AC-HF＜AC-HCl＜AC-HNO3＜AC-H2SO4. The methylene blue adsorptionvalue of modified activated carbons was: AC-HNO3＜AC-HF=AC-HCl=AC-H2SO4.(3) The supercapacitor assembled with above activated carbon had electric doublelayer capacitance characteristics and excellent efficiency of charging and discharging(more than97%). The increase of specific surface area could improve the specific capacitance of supercapacitor, when increased to a certain value, the supercapacitorobtained higher specific capacitance of235.1F/g at the conditions that the averagepore diameter of activated carbon was close to1nm in the electrolyte ion solvent.The specific capacitance of supercapacitor assembled with modified activatedcarbons was: AC-HCl＞AC-HF＞AC-H2SO4＞AC-HNO3. The high ash content ofmodified activated carbon would reduce the specific capacitance of supercapacitor.The specific capacitance of supercapacitor might increase with carbonyl anddecrease with carboxyl and hydroxyl groups.