Polyaniline nanowire array encapsulated in titania nanotubes as a superior electrode for supercapacitors

Abstract

Conducting polymer with 1D nanostructure exhibits excellent electrochemical performances but a poor cyclability that limits its use in supercapacitors. In this work, a novel composite electrode made of polyaniline nanowire–titania nanotube array was synthesized via a simple and inexpensive electrochemical route by electropolymerizing aniline onto an anodized titania nanotube array. The specific capacitance was as high as 732 F g⁻¹ at 1 A g⁻¹, which remained at 543 F g⁻¹ when the current density was increased by 20 times. 74% of the maximum energy density (36.6 Wh kg⁻¹) was maintained even at a high power density of 6000 W kg⁻¹. An excellent long cycle life of the electrode was observed with a retention of ∼86% of the initial specific capacitance after 2000 cycles. The good electrochemical performance was attributed to the unique microstructure of the electrode with disordered PANI nanowire arrays encapsulated inside the TiO₂ nanotubes, providing high surface area, fast diffusion path for ions and long-term cycle stability. Such a nanocomposite electrode is attractive for supercapacitor applications.