| The high surface area activated carbon (HSAAC) was prepared from petroleum coke and bamboo charcoal by the activation of alkali metal hydroxide. The influences of the source and structure of carbonaceous materials, the activated agent of different kinds and its ratio, the ratio of the activated agent of different kinds and carbonaceous materials, the activated temperature, the activated time on capacitance characteristic, adsorption properties and pore structure of HSAAC had been investigated. Base on these, the technologic methods and conditions of controlling structure and properties of HSAAC had been established. The morphology of HSAAC was observed by scan electric microscope and its specific surface area (BET) and pore structure were determined by adsorption method of low temperature nitrogen. The relations of specific capacitance of HSAAC and its specific surface area (BET), pore structure, adsorption properties were discussed. Using the activated carbon as the electrode materials of electric double-layer capacitor (EDLC), charge and discharge properties and the relations of the properties of EDLC and specific surface area, pore structure, adsprption properties of HSAAC were discussed.Experiment results show that the best technologic conditions of preparing HSAAC with petroleum coke by the activation of KOH using muffle furnace in laboratory are the ratio of petroleum coke and KOH, activation temperature and activation time being 4, 900 and 1 hour respectively. The specific capacitance of the HSAAC reaches 53F/g and its BET surface area, iodine adsorption value and methylene blue adsorption value are 2598m2/g, 2116mg/g and 582mg/g respectively. The best technologic conditions of preparing HSAAC with petroleum coke by the activation of KOH using enlarged equipment are the ratio of petroleum coke and KOH, activation temperature and activation time being 4, 800 and 3 hour respectively. The specific capacitance of the HSAAC reaches 81F/g and its BET surface area and iodine adsorption value are 3203m2/g and 2029mg/g respectively. The EDLC, using the HSAAC prepared by enlarged equipment as electrode materials, has excellent properties except that capacitance drops when discharging at big current density and ithas reached the requirement of energy storage component.The best technologic conditions of preparing HSAAC with bamboo charcoal carbonized at 700 by the activation of KOH using muffle furnace in laboratory are the ratio of bamboo charcoal and KOH, activation temperature and activation time being 4, 900 and 1 hour respectively. The specific capacitance of the HSAAC reaches 52F/g and its BET surface area, iodine adsorption value and methylene blue adsorption value are 3200m2/g, 2300mg/g and 570mg/g respectively. The main reason that BET surface area and iodine adsorption value of bamboo charcoal based HSAAC are larger than petroleum coke based HSAAC is bamboo charcoal having more loosen structure and content of amorphous carbon.The catalysis activity of KOH is super to NaOH when using single alkali metals hydroxide as activated agent. However, there is some cooperation effect between K and Na when using mixed alkali metals hydroxide as activated agent. The HSAAC with excellent capacitance characteristic and good adsorption properties can be obtained by controlling the ratio of KOH and NaOH.There are closer relations between capacitance characteristic of HSAAC and its adsorption properties and pore structure. With increasing of iodine adsorption value and methylene blue adsorption value, the specific capacitance of HSAAC increased. The suitable pore diameter ranges from 2nm to ,5nm for H2SO4 electrolyte.Using the HSAAC as electrode materials, the EDLC has good charge and discharge properties. It can discharge not only at the small current condition and long time, but also at the large current condition and short time. It also has excellent cycle stability. The capacity of EDLC drops no more than 5 percent after 700 cycles. But with the increasing of current density, the specific capacit... |
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