Supercapacitor studies on globular polypyrrole microstructures developed by a facile electrochemical route

Abstract

Micrometre-scale polypyrrole (PPy) structures are synthesised for electrochemical supercapacitor applications by a facile electrochemical route. Globular polypyrrole microstructures of size <5 µm are grown on stainless steel (SS-304) substrate by electro-polymerisation of pyrrole on oxygen microbubble templates electrochemically generated and stabilised in the presence of surfactant/supporting electrolyte/dopant β-naphthalene sulfonic acid (β-NSA). Microstructures obtained with scan range of 0–1.6 V (against Ag/AgCl) are uniformly distributed over the surface with high coverage density of 5×105 to 8×10 cm−2. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed that the formed microstructures are of β-NSA doped PPy. Scanning electron microscopy showed the uniform spread and good coverage of microstructures over the substrate. Supercapacitor properties of PPy films are investigated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge methods with 1.0 M KCl as electrolyte in a three-electrode electrochemical cell. Specific capacitance of 583 Fg−1 is obtained, which is greater than the values (350–400 Fg−1 highest) usually reported for this material. Electrochemical impedance spectroscopy proves the supercapacitance behaviour and explains the special inductive component of impedance observed in the high-frequency regime because of the globular structures of PPy deposited