Acid‐doped polyaniline and its vertically aligned SWCNT composites: Influence of acid type and concentration on structural and electrochemical properties

Abstract

This study explores how acid type (hydrochloric acid [HCl], p‐toluenesulfonic acid [TSA], and formic acid [FA]) and concentration affect the structure of polyaniline (PANI) and the electrochemical properties of its composite with vertically aligned single‐walled carbon nanotubes (SWCNTs). PANI doped with TSA (PANI‐TSA) exhibited improved dispersion and conjugation attributed to the larger anion volume, which mitigates interchain spacing, in contrast to PANI doped with HCl (PANI‐HCl) and FA (PANI‐FA). Additionally, varying the organic acid concentration affected PANI's morphology and the concentration of quinone structure, with TSA leading to a fibrous structure and enhanced electrochemical characteristics. The study further investigated the SWCNTs/PANI composite, revealing that higher TSA concentrations enhance conductivity and specific capacitance of the composite membrane due to sulfonic acid group. Notably, HCl‐based SWCNTs/PANI only at higher acid concentrations exhibits superior electrochemical characteristics than TSA‐based SWCNTs/PANI, achieving charge transfer resistance down to 5.514 Ω cm2 at 1.0 mol/L. Moreover, applying an electric field during membrane synthesis significantly increased the specific capacitance of composite prepared with PANI‐TSA, highlighting the role of voltage in optimizing electron transport efficiency within the composite.