Facile synthesis of graphene paper/polypyrrole nanocomposite as electrode for flexible solid-state supercapacitor

A green and facile method was adopted to fabricate graphene paper (GrP) decorated with polypyrrole (PPy) as supercapacitor electrode material. Polypyrrole was deposited on GrP at room temperature via one-step electropolymerization of 5% pyrrole with 0.5 M H2SO4 as electrolyte solution in a three-electrode configuration using GrP, platinum wire, and Ag/AgCl (1 M KCl), as working electrode, counter electrode and reference electrode, respectively. Different cyclic voltammetry (CV) deposition cycles (1, 3, 5, 8, 10 and 15) were applied under constant potentials in the range of 0.0 to 1.0 V at a scan rate of 30 mV/s. Successful electropolymerization of PPy onto GrP was confirmed via analytical (FT-IR, XPS and Raman spectroscopies), electrochemical (CV, electrochemical impedance spectroscopy), and morphological (scanning electron microscopy) characterizations of the fabricated GrP-PPy nanocomposite. Based on the CV data obtained in a three-electrode system, among the as-prepared electrodes those prepared with eight deposition cycles of PPy (GrP-PPy/8) produced the best supercapacitance performance. A flexible asymmetric all-solid-state supercapacitor device (AASD) was fabricated with GrP-PPy/8 as positive electrode and GrP as negative electrode. The areal capacitance of the AASD was as high as 128.9 mF/cm(2) at current density of 0.1 mA/cm(2). The AASD also exhibited excellent energy density (16.1 mWh/cm(2)) and power density (180 mW/cm(2)); and its cyclic stability was over 85% after 5,000 consecutive galvanostatic charge/discharge cycles. These results point to a novel and fast route to fabricate free-standing and flexible supercapacitor devices.