Electrodeposition of polyaniline in long TiO2 nanotube arrays for high-areal capacitance supercapacitor electrodes

Abstract

Anodic TiO2 nanotube arrays (TNTAs) were found to be a suitable scaffold for the loading of other active materials for supercapacitors. The prepared coaxial nanostructured composite-based TNTAs have been reported to show a remarkable specific capacitance. However, owing to the semiconductive nature of TiO2 and the diffusion limits of electrolytes in nanotubes, the electrodeposition of active materials was often found to preferentially occur at the upper areas of TNTAs, resulting in insufficient pore filling especially for long nanotubes. Here, robust and long (over 100 μm) TNTAs are served as a support template for electrodeposition of polyaniline (PANI). After an electrochemical reduction process of TNTAs, uniform and complete pore filling with PANI using electrodeposition from bottom to top is realized by potentiodynamic cycling successfully. The obtained PANI/TNTAs composites show areal capacitances as high as 512.4 mF cm−2 due to the higher loadings of PANI. They also have relatively good rate capability and cycling stability. This work makes PANI/TNTAs composite electrodes really scalable.