Plasma synthesis of polyaniline enrobed carbon nanotubes for electrochemical applications

Highlights: • CNTs and PANI/CNTs electrodes prepared by RF-PECVD. • Ultra-thin film of PANI shows strong adhesion to CNTs. • PANI is presented in polyemeraldine based structure. • PANI/CNTs electrode retains 65% of initial specific capacitance until 5800 cycles. Radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) was employed to synthesize vertically aligned carbon nanotubes (VACNTs) using Ni catalyst on TiN/SiO₂/Si substrate. Subsequently, CNTs were covered by a thin film of polyaniline (PANI) applying RF-plasma polymerization method. The structure and chemical nature of the samples were identified by microscopic and spectroscopic techniques. Scanning electron microscopy (SEM) evidences the presence of a PANI thin film wrapping the surface of CNTs. X-ray photoelectron spectroscopy (XPS) reveals that PANI presents a polyemeraldine based structure. Raman spectroscopy results show the appearance of fluorescence caused by a thin film of PANI over the carbon nanotubes. VACNTs and PANI enrobed VACNTs were electrochemically tested for supercapacitor applications in 0.2 M Na₂SO₄ electrolyte solution. VACNTs and PANI/CNTs electrodes deliver specific capacitances of 12 F/g and 1225 F/g respectively, at a scan rate of 5 mV/s. Cycling stability results show that at 15 A/g current density, PANI/CNTs composite retains 65% of the initial specific capacitance (410 F/g) after 5800 cycles.