Exploring the Synergistic Effects of Ultrafine Polyaniline Nanofibers and Oxygen-Modified Multi-Walled Carbon Nanotubes on Enhancing Pseudocapacitive Electrochemical Performance for Advanced Supercapacitors

This work reports a systematic study concerning the synthesis of pure polyaniline ultrafine nanofibers (PANI-NFs) and their nanocomposites with oxygen-functionalized carbon nanotubes (PANI-NFs/O-MWCNTs) using diluted chemical polymerization and hydrothermal processes. We investigated the synergistic effects of various synthesis parameters, such as the concentration of the ammonium persulfate oxidant agent and growth temperature, on the physical, chemical, and electrochemical properties of the resulting products through structural, morphological, spectroscopic, and electrochemical characterization. Our study revealed the successful synthesis of thermally resistant polyaniline ultrafine nanofibers (PANI-NFs) in the form of emeraldine salt (ES), exhibiting a mean diameter in the range of 8–17 nm. The PANI-NFs and PANI-NFs/O-MWCNT nanocomposites demonstrated excellent electrochemical properties, with specific capacitances of up to 0.94–1.23 F cm−2 and 1410–2074 F/g, respectively, and with good rate capability. These characteristics are confirmed by the relaxation time constant τ0 (41 and 8 ms, respectively) and lower internal R0/interfacial charge transfer RՓ resistances of around 0.2 Ω, as well as diffusion coefficients of around 10−7 and 3.7 × 10−7 cm2/s. This breakthrough in nanofiber synthesis paves the way for practical applications in diverse domains, from high-performance energy storage to biosensing and beyond, where the unique electroactive properties of the nanocomposites can be leveraged to achieve exceptional results.