Polypyrrole nanocomposites doped with functional ionic liquids for high performance supercapacitors

Abstract

In this study, functional ionic liquids (ILs) composed of carboxyl or sulfonic groups were fabricated as dopants for polypyrrole (PPy) nanocomposites. These novel nanocomposites could be conveniently prepared via chemical oxidation polymerization of pyrrole (Py) using FeCl₃·6H₂O as the oxidant. The as-prepared IL@PPy nanocomposites were examined using Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption isotherm measurements. SEM images revealed that the schistose nanostructure could be obtained when PPy was doped with 1-vinyl-3-carboxymethylimidazole chloride ([VCMIm]Cl). Electrochemical performances of electrode materials based on IL@PPy were investigated via cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The results demonstrated that the electrochemical properties of IL@PPy nanocomposites were significantly influenced by their composition. Especially, a comparably high specific capacitance (520 F g⁻¹ at the current density of 0.5 A g⁻¹) could be achieved when [VCMIm]Cl@PPy nanocomposites were prepared with the feed ratio of [VCMIm]Cl to Py of 3 : 1 (mol mol⁻¹). Their good electrochemical performance probably resulted from the schistose nanostructure. Cycling performance measurements indicated that 82% capacitance could be retained after 800 cycles in 1.0 M KCl aqueous solution. Therefore, it is anticipated that our strategy opens up a new avenue for fabricating PPy nanocomposites for high performance supercapacitors.