Polypyrrole directly bonded to air-plasma activated carbon nanotube as electrode materials for high-performance supercapacitor

Novel polypyrrole (PPy)-bonded carbon nanotube (CNT) composites were synthesized directly using air-plasma activated CNTs, via in situ chemical oxidative polymerization. The morphology, surface groups, and thermal stability of the composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA), respectively. The electrochemical properties of electrodes made by the composites were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The results show that the PPy uniformly coated on the surface of air plasma-activated CNTs. The TGA and FTIR analyses confirm the improved thermal stability and conductivity of the composites, respectively. The composites of PPy and plasma activated CNT (P-CNT-PPy) show a greater specific capacitance, and a smaller Rct resistance than the composites of PPy and CNT (CNT/PPy). The specific capacitances of P-CNT-PPy and CNT/PPy electrodes are 188 and 148 F/g in 1 M KCl, and 264 and 210 F/g in 1 M H2SO4, respectively. After charge-discharge tests for 1000 cycles at a current density of 5 mA/cm2, the P-CNT-PPy electrode retains 89% of its initial capacitance while the CNT/PPy retains 76%. Thus, the P-CNT-PPy demonstrated as a promising electrode material for high-performance supercapacitors.