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Preparation Of Carbon Electrode Material From Petroleum Coke Activated By NaOH For EC

Posted on:2008-08-07Degree:MasterType:Thesis
Country:ChinaCandidate:G F YaoFull Text:PDF
GTID:2132360245993387Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Carbon materials are widely used as electrode materials of electrochemical capacitor(EC) due to it's unique properties, such as low-cost, stability. Petroleum coke based carbon electrode materials for EC were prepared by NaOH activation in this work and the conditions were optimized. The SEM, XRD and N2 adsorption at 77K were used, respectively, to detect the structure of as-obtained carbon materials Constant current charge/discharge cycle, cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrochemical proprieties of the carbon materials.Direct activation process was used to prepare the petroleum coke based carbon electrode materials and the effect of activation temperature and activation time on the structures and electrochemical properties of activated carbons were studied. The results show that the as-received materials were layer and ordered structure and the materials were activated at 700℃had the highest porosity, activated at 800℃exhibited the best capacitance properties, and with prolonging activation time at 800℃from 1h to 3h, the specific surface area and total volume decreased along with the enlargement of average pore size. The porous carbon activated at 800℃for 3h exhibited the best capacitance characteristics, its specific capacitance of 110 F·g-1 at 50 mA·g-1 and 79 F·g-1 at 2 A·g-1, respectively. The decrease of specific capacitance is only 4.7% between 150~1000 charge/discharge cycles at 100 mA·g-1 current density.Petroleum coke based nanogate carbon electrode materials for electrochemical capacitor was prepared by carbonization-activation process and the effect of carbonization temperature and carbonization time on structure and electrochemical properties were investigated. Nanogate structure could be obtained at the carbonization temperature of 800℃and 900℃. The as-obtained materials exhibited an"electrochemical activation"process at the first charge/discharge cycle. With prolonging carbonization time at 800℃from 1h to 3h, the d002 of as-obtained nanogate carbon materials decreased from 0.380nm to0.363nm and no obvious change of pore structure were observed. All of the materials showed excellent capacitance characteristics. The specific capacitance increased with carbonization time when current density is lower than 200mA·g-1. On the contrary, when current density is higher than 1500mA·g-1, the specific capacitance decreased with carbonization time. At the first several charge/discharge cycles, the specific capacitance reduced obviously. But after 100 cycles, the decrease of specific capacitance was very weak.The capacitance characteristics of petroleum coke based porous carbon and nanogate carbon were compared, the results show that all the petroleum based porous carbon showed higher specific capacitance, less capacitance reduce at high charge/discharge current density, and stable cycle properties and the conditions for preparing the nanogate carbon materials needed to be further optimized.
Keywords/Search Tags:Petroleum coke, Electrochemical capacitor, Chemical activation, Porous carbon, Nanogate carbon
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