Supercapacitor based on H+ and Ni2+ co-doped polyaniline–MWCNTs nanocomposite: synthesis and electrochemical characterization

Abstract

In the search for promising electrode materials for supercomputer applications, we have synthesized a Ni²⁺ doped polyaniline, and a nanocomposite based on multiwalled carbon nanotubes (MWCNTs) and a Ni²⁺ doped polyaniline (PANI) in a HCl medium by an in situ oxidative polymerization. In the HCl medium and in the presence of Ni²⁺, PANI becomes co-doped with both H⁺ and Ni²⁺. The as synthesized materials were characterized by FTIR and Raman spectroscopy and an XRD study. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses confirmed the successful coating of the co-doped PANI on the MWCNT surface. The electrochemical characterizations were carried out by a three electrode system, with 1 M H₂SO₄ as the electrolyte. The PANI co-doped with H⁺ and Ni²⁺exhibited a specific capacitance of 311 F g⁻¹ at a 0.5 A g⁻¹ constant current, which was higher than that of the solely H⁺ doped PANI, which exhibited a specific capacitance of 265 F g⁻¹ under the same conditions. The incorporation of MWCNTs to the co-doped PANI influenced the specific capacitance to increase to 781 F g⁻¹ at the same constant current density, with a 92% retention of initial specific capacitance over 700 galvanostatic cycles.