Synergistic design of gadolinium-doped polyaniline/MWCNT hybrid nanocomposites for high-performance supercapacitors

A nanocomposite comprising gadolinium-doped polyaniline integrated with multiwalled carbon nanotubes was synthesized using an in-situ oxidative polymerization approach and explored for its potential use in supercapacitor devices. Structural evaluation through FT-IR spectroscopy revealed a quinoid/benzenoid ratio of 0.6116, indicating effective polymerization and interaction between the components. X-ray diffraction analysis showed a crystallite size of approximately 16 nm, with the material exhibiting a high degree of crystallinity at 95%, reflecting well-structured ordering within the composite. Thermal stability and decomposition behavior were examined using thermogravimetric analysis. The Gibbs free energy, enthalpy, entropy and activation energy were calculated using the thermodynamic parameters, confirming robust thermal resistance and strong interactions among the constituents. Scanning electron microscopy revealed a highly porous and interconnected surface morphology, which supports rapid ion mobility. Electrochemical test results including cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy demonstrated a strong charge storage capacity, with a specific capacitance of 280 F g⁻1 at a scan rate of 1 mV s⁻1 using 1 M H₂SO₄ as an electrolyte. The composite also displayed low charge transfer resistance (19.54 Ω), minimal Warburg impedance (0.0406 Ω) and excellent reversibility, indicating its suitability for high-efficiency energy storage applications.