Effects of different anionic dopants on the charge storage properties of binder less polypyrrole/vertically aligned carbon nanotube composites

In this paper, a polypyrrole/vertically aligned carbon nanotube (PPy/VACNT) composite has been prepared by in situ chemical polymerization of pyrrole precursor on the surface of VACNT electrode. VACNTs has been prepared by plasma enhanced chemical vapor deposition (DC-PECVD) from a mixture of H₂ and C₂H₂ and were used as 3D nanoporous substrates. Effects of different dopant anions on the charge storage properties of PPy have been studied in this work. Camphor sulfonic acid, α-naphthalene sulfonic acid, anthraquinone-2-sulfonic acid sodium salt monohydrate/5-sulfosalicylic acid dehydrate, Sodium dodecylbenzenesulfonate and sodium dodecyl sulfate were used as anionic dopants. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction were used to characterize the electrodes. Cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy technique in 1 M HCl electrolyte were applied to investigate the electrochemical properties of electrodes. The results showed the specific capacity of electrodes was found to be in the order of the mentioned dopants at 10 mV s⁻¹ scan rate. A maximum specific capacity of 332 C g⁻¹ was obtained with PPy/VACNT which was doped with camphor sulfonic acid at 10 mV s⁻¹ scan rate. In addition, the specific capacity of this electrode increased during cycling in 1 M HCl electrolyte which shows excellent cyclic life. The results show PPy-CSA/VACNT composite electrode have excellent characters of an electrode as a consequence of porous network structure and high electrochemical conduction which provides straight and fast ion transport pathways.