Preparation Of Activated Carbon From Starch And Its Application In Super-Capacitors

Activated carbon is considered as one kind of the super capacitorelectrode materials for its large surface area, chemical stability and goodelectrical conductivity properties. The samples of starch-based activatedcarbon prepared by the phosphate activation method andphysical-chemical compound method are less pollution and less corrosion.This paper focuses on how to change the process to develop the pore,improve surface area of activated carbon, and be better to form the ratioof the electric double layer hole in order to improve the electro chemicalperformance of activated carbon. The main process is as follows︰1、Activated carbon was prepared from starch using phosphoric acid(H3PO4) activation and physical-chemical compound activation methods.It was studied that preparation processes affect pore structure. The porestructure, surface area and surface morphology of activated carbon werecharacterized by iodine adsorption, N2adsorption, FTIR and scanningelectron microscopy (SEM) respectively. The results show that theactivation temperature is the crucial factor in the process of activated carbon prepared by phosphoric acid. With activation temperatureincreasing, the specific surface area is smaller beginning and thenincreasing. The surface area of activated carbon prepared at temperatureof850℃reached970m~2/g. The surface area of the starch-based activatedcarbon with the method of physical-chemical compound activation at atemperature of850℃and the activation time of2hours is up to1438m~2/g.2、Activated carbon is used to produce electrodes, and then cyclicvoltammetry, constant current charge and discharge and AC impedanceare used to measure the electrochemical properties. The results show thatthere is no linear relationship between surface area and specificcapacitance. The surface area of activated carbon activated at550℃was572m~2/g, while capacitance of the sample reaches138F/g. The specificcapacitance of activated carbon produced with physical-chemicalcompound activation method at the temperature of850℃and30minactivation time reaches158F/g.3、Starch-based activated carbon is used as electrode material, andfoam nickel, stainless steel mesh and graphite paper are used for currentcollector of electrode. Electrochemical performances of electrodes aretested. The results show that electrochemical performance of electrodeswith graphite paper is the best performance of capacitance and cyclestability, and its specific capacitance of200F/g.