Porous carbon nanofibers (CNFs) with high energy storage performance were fabricated with a single precursor polymer, 6FDA-TFMB, without the use of any pore-generating materials. 6FDA-TFMB was synthesized, electrospun, and thermally treated to produce binder-free CNF electrodes for electrochemical double-layer capacitors (EDLCs). Highly porous CNFs with a surface area of 2213 m(2)g(-1)were prepared by steam-activation. CNFs derived from 6FDA-TFMB showed rectangular cyclic voltammograms with a specific capacitance of 292.3 F g(-1)at 10 mV s(-1). It was also seen that CNFs exhibit a maximum energy density of 13.1 Wh kg(-1)at 0.5 A g(-1)and power density of 1.7 kW kg(-1)at 5 A g(-1), which is significantly higher than those from the common precursor polymer, polyacrylonitrile (PAN).