ZnO-containing porous activated carbon nanofibers (ZnO/ACNFs) are prepared through one-step electrospinning using zinc acetate and polyacrylonitrile (PAN), followed by thermal treatment. The electrochemical performance of the ZnO/ACNF composite electrodes is compared to that of pure ACNF electrodes in aqueous KOH as the electrolyte. Electrochemical measurements of ZnO/ACNFs reveal a maximum specific capacitance of 178.2 Fg(-1), and high energy densities of 22.71-17.77 Whkg(-1) in the power density range of 400 to 4000 W kg(-1). Furthermore, this supercapacitor electrode exhibits excellent cycle life with a specific capacitance similar to 75% of the initial value after 1000 cycles. The combination of ACNF's high surface area with ZnO's large specific capacity facilitates a synergistic effect between ZnO's faradaic capacitance and ACNF's double layer capacitance, which afforded good capacitive behavior. (C) 2014 Elsevier B.V. All rights reserved.