Effect of Inter-Electrode Spacing on Electrolyte Properties and Morphologies of Anodic TiO2 Nanotube Array Films

This work presents the formation of TiO2 nanotube arrays fabricated by electrochemical anodization of titanium in the fluoride-based diethylene glycol (DEG) electrolyte, with an aim towards elucidating how variation of inter-electrode spacing affects changes in electrolyte properties and corresponding morphological features of TiO2 nanotube array films. Enlargement of nanotube morphologies of DEG fabricated nanotubes is attainable through a simplified synthesis technique and manipulation of electrolyte properties. Electrolyte conductivity and titanium concentration are found to drastically increase with decreasing anode-cathode separation. Resulting titania nanotube array morphologies also tends to increase significantly, particularly observed in intertubular spacing that increases by a factor of 15 as reducing the electrode spacing from 4.5 cm to 0.5 cm under a fixed electrolyte condition. Due to the combination effect of electrolyte properties and high field strength between the electrodes, the self-enlargement potential is believed to be a driving force for nanotube separation. The unique characteristic of discrete, well-separated nanotube structure is expected to extend and enhance the applications of anodic TiO2 nanotube array films.