Preparation and electrochemical performance of the N-doped hollow pitch-based activated carbon fibers as supercapacitor electrodes

摘要

Mixtures of polyethyleneimine (PEI) and ethylene tar pitch (0, 15, 20, 30 wt% of PEI) were melt-spun, stabilized, carbonized and activated to prepare nitrogen-doped (N-doped) activated carbon fibers ( ACFs). The morphology, porous structure and surface chemistry of the N-doped ACFs were characterized by N, adsorption, XPS and SEM. Their electrochemical performance as supercapacitor electrode materials was investigated. Results indicate that the specific surface area, pore volume and number of nitrogen-containing functional groups of the N-doped ACFs are much increased compared to undoped ACFs. PEI pyrolysis during the carbonization of the fibers leads to the formation of hollow N-doped ACFs that increases the utilization % of the surface area, resulting in a significant increase of the specific capacitance. When 20 wt% PEI was added, the specific surface area of the N-doped ACF reached 2 756 m2/g, its pore sizes ranged from 0. 7 to 2 nm, and its specific capacitance reached 314 F/g at 0.5 A/g, which is much higher than that (194 F/g) of the undoped ACF.