Preparation and characterization of N, S-codoped activated carbon-derived asphaltene used as electrode material for an electric double layer capacitor

N, S-codoped activated carbon was derived from asphaltene by potassium hydroxide and used as an electrode material for electric double-layer capacitors. The samples contained elements such as nitrogen and sulfur, which enhanced the positive effects on capacitance through improved electron transfer, and could be used without pretreatment. The obtained activated carbon contained both nitrogen (1.17 wt.%) and sulfur (0.32 wt.%) after an activation process. Also, it had a high surface area of 2558 m(2)/g and a mosopore volume of 0.98 cm(3)/g, while raw asphaltene and asphaltene activated at 700 degrees C exhibited high levels of heteroatoms and a low BET surface area. The activated carbon derived from asphaltene showed a high specific capacitance of 128 F/g at 0.5 A/g in 1 M tetraethylammonium tetrafluoroborate compared with other samples. Thus, the capacitances of electrode materials depend on the concentration and species of heteroatoms and also the microstructure, such as BET surface area and mesopore volume.