Well-matched electrochemical performances of TiO2 nanotubes based on Ti wires with strong adhesion to Ti substrate

Anodic TiO2 nanotubes (ATNTs) fabricated by anodization of Ti foils have been investigated for many years due to unique structure and excellent electrochemical performance. However, nanotube arrays fabricated on Ti foils are prone to peeling, which is one of the critical defects for applications. To overcome this challenge, the nanotubes on Ti wires are fabricated for the first time, for which the cylinder shape can neutralize stress between ATNTs and Ti substrate. The influences of anodizing temperature and NH4F concentration on morphology and electrochemical performances of ATNTs fabricated on Ti wires and Ti foils, are explored and compared in detail. There are many remarkable differences between anodization processes on Ti wires and Ti foils. The anodizing current density-time curves of ATNTs fabricated on Ti wires present a slow and stepwise decrease at the quasi-steady state and corresponding FESEM images show that ATNTs with numerous halfway-terminated nanotubes were growing in a radial direction on the circumference of Ti wires, much different from ATNTs fabricated on Ti foils. The electrochemistry behaviors (supercapacitor performance) of ATNTs fabricated on Ti wires and Ti foils were studied by cyclic voltammetry and galvanostatic charge-discharge tests. The results demonstrate that the nanotubes fabricated on Ti wires show stronger adhesion strength and stable performance, thus paving the way for the application of ATNTs.