85 MeV C6+ swift heavy ion irradiation of in-situ reduced graphene oxide–polypyrrole nanotubes nanocomposite films for supercapacitor electrodes

Abstract

Hybrid nanocomposites of reduced graphene oxide (RGO) and polypyrrole nanotubes (PPyNTs) have been synthesized by in-situ reduction of graphene oxide. The nanocomposite films are modified by swift heavy ion irradiation with 85 MeV C6+ ions at different fluences of 6 × 1010, 3.6 × 1011, 2.2 × 1012 and 1.3 × 1013 ions cm−2. Morphological, structural, thermal and electrical properties of the irradiated nanocomposites have been investigated by FESEM, HRTEM, XRD, thermogravimetric analyzer and conductivity measurements. The BET specific surface area and porosity of the nanocomposites have been determined by N2 adsorption-desorption measurements. The fluence dependent electrochemical performance of the irradiated nanocomposites as electrodes has been studied by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. The electrochemical studies reveal that the capacitive properties improved upto a fluence of 2.2 × 1012 ions cm−2 and decreases at higher fluence. A highest specific capacitance of 346 F g−1 and cyclic stability of 89% is achieved for the irradiated nanocomposite compared to 299 F g−1 and 77% of that of pristine. The increase of capacitive performance may be ascribed to the increase in surface area and pore size of the pristine electrode with increasing irradiation fluence, which extends the ion transport from the surface to the bulk of the electrode. Decrease in the diameter of PPyNTs is observed from FESEM images with increase in ion fluence, which may also contribute to higher charge storage by increasing the overall surface area of the electrode.