Electrochemical properties of leucoemeraldine, emeraldine, and pernigraniline forms of polyaniline/multi-wall carbon nanotube nanocomposites for supercapacitor applications

We report on the synthesis and electrochemical properties of leucoemeraldine base, emeraldine salt and pernigraniline base forms of polyaniline (PANI) in the form of nanocomposites with MWNTs. The oxidation state of PANI in the composite is controlled by doping and dedoping of the emeraldine salt form of PANI/MWNT composite, which is prepared through chemical polymerization, using oxidizing and reducing agents without changing the morphology of PANI in the composite and is confirmed by ultraviolet–visible spectroscopy (UV–vis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical and pseudocapacitive properties of the composites are investigated using cyclic voltammetry and analyzed with respect to the oxidation state of polyaniline. The PANI/MWNT nanocomposites show specific capacitance values of 217 F g−1, 328 F g−1 and 139 F g−1 for leucoemeraldine base, emeraldine salt and pernigraniline base, respectively. Electrochemical impedance spectroscopy is performed to explain the different electrochemical properties of PANI in different oxidation states.

► Nanocomposites of MWNT and polyaniline (PANI) with different oxidation state: leucoemeraldine base (LB), emeraldine salt (ES) and pernigraniline base (PB) forms for supercapacitors.
► Oxidation state of PANI in the composite controlled by chemical oxidation and reduction of ES/MWNT without causing morphology change of PANI and confirmed by UV and FT-IR analysis.
► Electrochemical properties of LB/MWNT, ES/MWNT and PB/MWNT evaluated using CV and EIS in H2SO4 for supercapacitors.
► Different pseudocapacitive properties depending on the oxidation state of PANI in the composite.