Effects of pore structures on electrochemical behaviors of polyacrylonitrile (PAN)-based activated carbon nanofibers

• We report the effects of KOH activation on pore development of activated carbon nanofibers (ACNFs).
• ACNFs showed enhanced specific surface area from 480 to 1160 m2/g with mesopore-rich pore structure.
• The samples containing high mesopores fraction showed better specific capacitance than the samples containing low mesopores fraction at similar specific surface area.

In this study, activated carbon nanofibers (ACNFs) were prepared for supercapacitor electrode applications by using nanosize polyacrylonitrile (PAN) fibers as a precursor, following treatments under various activation conditions. The surface morphologies and structural characteristics of the ACNF were observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The N2 adsorption isotherm characteristics at 77 K were confirmed by Brunauer–Emmett–Teller (BET) and Dubinin–Radushkevich (DR) equations. The mesopore size distributions of the samples were obtained by Barrett–Joyner–Halenda (BJH) equation. The ACNFs were applied as an electrode for electrical double-layer capacitors and analyzed in relation to the activation conditions. SEM analysis confirmed that many pores or excessively-oxidized structures were found on the fiber surfaces after KOH activation. The specific surface areas and specific capacitance of the prepared ACNFs were enhanced with increasing activation time.