Carbon–polyaniline coaxial structures for enhanced charge transfer and capacitance in supercapacitors

Abstract

Polyaniline (PANI) is widely used as a pseudocapacitive material in supercapacitors. However, PANI exhibits limited capacitance due to its poor electrical conductivity and low specific surface area. In this study, coaxial structures composed of silver nanowires (AgNWs) as the core, subsequently deposited with a carbon layer and PANI nanowires via in situ polymerization, were fabricated. Scanning electron microscopy revealed that the structures had an average diameter of 181 ± 57 nm and a length of 1.2 ± 0.6 μm. X-ray photoelectron spectroscopy analysis verified the successful formation of PANI on the outer layer of the structures, with fully benzenoid units and protonated amines. Raman spectra confirmed the deposition of sp²-hybridized carbon layers on the AgNW cores. Electrochemical impedance spectroscopy and galvanostatic charge–discharge (GCD) measurements revealed an improved charge transfer resistance (R_ct) of 1.43 Ω and a specific capacitance of 184 F g⁻¹, respectively, highlighting the role of the carbon layer in enhancing R_ct. After 3000 charge–discharge cycles using a Swagelok model, a capacitance loss of 47% was observed. Cyclic voltammetry measurements, combined with the Dunn method, indicated that the coaxial structures exhibited both electric double-layer capacitance (EDLC), contributing 69%, and pseudocapacitance from redox reactions in PANI. In addition, the coaxial structure was successfully deposited on a flexible ITO-coated PET substrate and subjected to 3000 GCD cycles. The fabricated AgNWs–carbon–PANI coaxial structures exhibited superior charge-storage performance compared to bulk PANI, underscoring their potential for practical energy storage applications in flexible devices.