Redox-active phenol red-infused polypyrrole@MWCNT composites for high-performance symmetric supercapacitors

Abstract

A hybrid composite material composed of multi-walled carbon nanotubes (MWCNTs) decorated with polypyrrole (PPy) and redox-active phenol red (PR) counter-anions was successfully synthesized in a straightforward route using an ethanol medium. The fabricated hybrid composite combines the electrical conductivity of conducting polymer PPy, the structural support with the additional conductivity of MWCNTs, and infusion of redox active counter anion PR into the polymer chain to enhance the overall electrochemical energy storage performance. The physicochemical properties of the synthesized PPy_PR@MWCNT material were thoroughly characterized by a wide range of techniques, including Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS), which provides insights into the material's structure, morphology, and chemical composition. Electrochemical performance was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The PPy_PR@MWCNT electrode exhibited a high specific capacitance of 393.4 Fg−1 at 0.5 Ag−1 in a three-electrode system. Additionally, the PPy_PR@MWCNT-based symmetric supercapacitor (SSD) demonstrated excellent long-term stability, retaining 88.0 % of its capacitance after 20,000 cycles. © 2025 Elsevier Ltd