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The electrochemical performances of an electrical double layer capacitor were investigated regarding the activated carbon prepared from bamboo by a new approach, that is, the combination of delignification, addition of guanidine phosphate, and CO activation. In this study, a 1 M HSO aqueous solution was used as the electrolyte of the capacitor. The physical properties, such as the BET specific surface area of the carbon material, depend on the preparation conditions of the activated carbon. A TEM image indicated that the addition of guanidine phosphate did not facilitate the graphitization and did not prevent activation by CO. The apparent reaction equation for the CO activation was first-order, which is reasonable for physical activation. The electrochemical performances of the carbon material depended on the preparation conditions of the carbon material, such as the heat treatment temperature, amount of added guanidine phosphate, and CO activation time. The sample prepared under the following conditions (the amount of added guanidine phosphate: 9 wt%, the heat treatment temperature: 800 °C, CO activation time: 3 h) had the highest performance (153 F g at 1000 mA g) because the sample had the highest BET specific surface area (2001 m g). [ABSTRACT FROM AUTHOR]

For the preparation of physically-activated carbons with ultra-high surface areas that are comparable to those of chemically-activated carbons, we synthesized meso-, macroporous carbons from phenolic resins using poly(methylmethacrylate) particles as a template and activated them using CO. Our aim was to achieve uniform activation by reducing the practical depth within the carbon which needs to be activated. Our results show that the shorter the practical depth becomes, the higher the achievable BET surface area becomes. Extremely high BET surface areas (~3000 m g) can be attained by reducing this depth to the order of a few tens of nanometers. We also relate the practical length of the developed nanopores with the practical depth through the results obtained from EDLC measurements. The results reveal that the shortening of the practical activation depth also leads to the shortening of the lengths of the nanopores introduced during activation. [ABSTRACT FROM AUTHOR]

Unconventional pretreatment, that is, delignification and the addition of guanidine phosphate, was performed for the synthesis of activated carbon having a high specific surface area from bamboo by physical activation. The values of the specific surface area, total pore volume, and average pore size depended on the amount of added guanidine phosphate and the CO activation time. The amount of the added guanidine phosphate under the optimum conditions for the highest specific surface area was much lower than that of the phosphorous acid chemical activator under conventional conditions. The N adsorption isotherms of all the samples were type I, which means that micropores were dominant. The pore sizes of the samples in this study were similar to that of the physically-activated carbon. Therefore, the activation process was presumed to be essentially not chemical, but physical. The relation between the yield and the specific surface area improved with the addition of guanidine phosphate. The reason for the improvement may be the change in the reactivity of the carbon material generated during the heating process. The maximum specific surface area was ca. 2000 m g, which is a high value for a physically-activated carbon. [ABSTRACT FROM AUTHOR]

Two substantially different carbonaceous precursors (Quercus Agrifolia wood and walnut shells) were processed following an identical carbonization-activation procedure, using CO2 as activating agent. Three activation temperatures were used and the evolution of micro and mesoporosity of produced samples as a function of activation yield is depicted. Differences, apparently given by intrinsic characteristics of precursors, were found in both the evolution and final status of porosity of obtained samples. It was concluded that initial properties of starting material strongly influence both course and results of the activation process under similar experimental condition. [ABSTRACT FROM AUTHOR]