Polyaniline-coated freestanding porous carbon nanofibers as efficient hybrid electrodes for supercapacitors

Three-dimensional, free-standing, hybrid supercapacitor electrodes combining polyaniline (PAN!) and porous carbon nanofibers (P-CNFs) were fabricated with the aim to integrate the benefits of both electric double layer capacitors (high power, cyclability) and pseudocapacitors (high energy density). A systematic investigation of three different electropolymerization techniques, namely, potentiodynamic, potentiostatic, and galvanostatic, for electrodeposition of PANI on freestanding carbon nanofiber mats was conducted. It was found that the galvanostatic method, where the current density is kept constant and can be easily controlled facilitates conformal and uniform coating of PANI on three-dimensional carbon nanofiber substrates. The electrochemical tests indicated that the PANI-coated P-CNFs exhibit excellent specific capacitance of 366 F g(-1) (vs. 140 F g(-1) for uncoated porous carbon nanofibers), 140 F cm(-3) volumetric capacitance, and up to 23 F cm(-2) areal capacitance at 100 mV s(-1) scan rate. Such excellent performance is attributed to a thin and conformal coating of PANI achieved using the galvanostatic electrodeposition technique, which not only provides pseudocapacitance with high rate capability, but also retains the double-layer capacitance of the underlying P-CNFs. (C) 2015 Elsevier B.V. All rights reserved.