Microstructural effect of various polyaniline-carbon nanotube core-shell nanocomposites on electrochemical supercapacitor electrode performance

Various carbon nanotubes-polyaniline (CNT-PANI) core-shell nanocomposites such as multiwalled carbon nanotube-PANI (PAM), carboxylic acid functionalized MWCNT (cMWCNT)-PANI (PACM) and aminefunctionalized MWCNT (nMWCNT)-PANI (PANM) core-shell composites are successfully prepared by in-situ chemical oxidation process using ammonium persulphate (APS). Fourier transform infrared spectrum (FTIR) analysis proves the bonding nature between CNT core and PANI shell in nanocomposites. High-resolution transmission electron microscopy (HRTEM) and Field emission scanning electron microscopy (FESEM) images confirm the nanometer-sized PANI layer over CNT or core-shell structure of CNT-PANI nanocomposites. Further, the specific capacitance of the PAM electrode is 647 Fg- 1 at scan rate 1 mV s-1 and 491 Fg- 1 at current density 1 Ag-1 through cyclic voltammetry (CV) and galvanostatic charge-discharge respectively (GCD) in H2SO4 (1 M) medium under an applied potential between -0.2 to +0.8 V. Among the other CNT-PANI core-sell electrodes, the PAM electrode exhibits the highest retention of specific capacitance of 98 % and maximum Coulombic efficiency of 100 % after 5000th cycles of galvanostatic charge-discharge in the same applied potential. Due to its high specific capacitance and exceptional capacitance retention, PAM composite was fabricated as symmetric supercapacitors. The highest specific capacitance of 483 Fg- 1 at a scan rate of 1 mV s-1 and 268 Fg- 1 at a current density of 1 Ag-1 in 6 M H2SO4 is found for PAM composite. The symmetric device delivered the maximum energy density of 37 Wh kg- 1 at a power density of 166 W kg- 1.