Preparation of separated and open end TiO2 nanotubes

Separated and open end TiO2 nanotubes with large surface area and through-hole structure exhibit exciting functionalities in energy and environmental applications. In this study, TiO2 nanotube membranes are created using high purity titanium sheets as raw materials by anodic oxidation at 100 V for 12 h in ethylene glycol+0.25 wt% NH4F+5 vol% H2O. The pore size of the nanotubes is 215 nm with uniform diameters. Close-packed TiO2 nanotube arrays are separated by immersion in a 0.15 wt% HF water solution. With further dissolution by 40% HF water solution for 10 min, the barrier layer at the back of the TiO2 nanotubes completely disappears and the nanotubes become open at both ends. This study offers a facile approach of making separated and open-end nanotubes for electrocatalytic purposes.