Polyaniline (PANI) nanofibers were fabricated by interfacial polymerization in the presence of para-phenylenediamine (PPD). The additives cannot only have a profound impact on the polymers morphology, but can also improve their specific energy and specific capacitances. It was found that PANI nanofibers prepared in the presence of PPD were longer and less entangled than those in the absence of PPD due to a much faster polymerization rate in initial stage. A specific capacitance value of 548 Fg(-1), a specific power value of 127W kg(-1) and a specific energy value of 36 Wh kg(-1) were obtained in polyaniline nanofibers prepared in the present of PPD at a constant discharge current density of 0.18 A g(-1). (C) 2010 Elsevier Ltd. All rights reserved.