Supercapacitors based on graphene-polyaniline derivative nanocomposite electrode materials

摘要

This manuscript discusses a comparative study of nanocomposite materials based on graphene and derivatives of PANI, i.e. 'methoxy' (-OCH_3) aniline and 'methyl' (-CH_3) aniline with graphene (G) for supercapacitor applications. The G-polyaniline (PANI), G-poly(o-methoxy aniline) [poly(o-anisidine) (POA)] and G-poly(o-methyl aniline) [poly(o-toluidine) (POT)] were synthesized by a chemical oxidative polymerization method and characterized to understand the nanocomposite formation of the materials. The electrochemical properties of G-PANI, G-POA, and G-POT nanocomposites based supercapacitors were investigated using cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) techniques in 2 M H_2SO_4 electrolyte. The specific capacitances (Cp) of supercapacitors based on G-PANI, G-POA, and G-POT in 2 M H_2SO_4 electrolyte were estimated to be 400, 380, and 425 F/g, respectively. However, POT nanocomposite with graphene exhibited better capacitance (425 F/g) than the G-polyaniline or the G-POA based electrode materials. The relaxation time constants of 0.6, 2.5, and 5 s for the G-POT, G-PANI, and G-POA nanocomposite-based supercapacitors were calculated from the EIS analysis and such time constants revealed a quicker delivery of the stored energy than the carbon-carbon based supercapacitors. The high specific capacitance and small relaxation time constants of the G-substituted polyaniline paved the way for the fabrication of safe and stable supercapacitors.