Effects of activation temperatures on the surface structures and supercapacitive performances of porous carbon fibers

Activated carbon fibers (ACFs) with uniform sub-nanometer pores (mainly < 1 nm) are obtained using a simple KOH chemical activation approach at lower temperature. The effects of activated temperature, especially lower temperature, on the morphology, structures, surface chemical states, pore structures, and supercapacitive performances of the ACFs are systematically investigated. The ACFs activated at 550 degrees C as the electrode material of supercapacitors exhibit superior specific capacitance (427 F g(-1) at 0.1 A g(-1)), good rate performance (294 F g(-1) at 10 A g(-1) and 248 F g(-1) at 20 A g(-1)), and excellent cycle stability (91.9% capacitance retention after 1000 cycles) in 6 M KOH aqueous solution. The outstanding charge storage capabilities are due to the suitable and larger specific surface area, high proportion of micropores and proper pore size. In addition, appropriate oxygen-containing functional groups also play important roles. Therefore, the high capacitance of activated carbon fibers is a synergy of pseudocapacitance and double-layer capacitance.