Effect of Electrolyte Pretreatment on the Formation of TiO₂ Nanotubes: An Ignored yet Non-negligible Factor

Tailoring the geometric configuration of anodic TiO₂ nanotubes enables their use in various applications. This paper demonstrates that the methods for pretreating electrolyte solutions significantly influence the growth of anodic nanotubes. Pretreatment is usually ignored by studies, but is a crucial and non-negligible factor in the control of nanotube growth. The results indicate that magnetic stirring and ultrasonic agitation facilitate the dissolution and mass transport of ionic species in the solution, resulting in a homogeneous solution and a high TiO₂ nanotube growth rate. Isolation of the solution from wide contact with the atmosphere through simple sealing further increases the growth rate. This is attributed to the hindrance of humidity absorption, which biases the original water content of the solution and thus causes the formation of an initial thick compact oxide layer that prevents ion diffusion. The findings can serve as a guide to electrolyte pretreatment routes for studying nanotube growth mechanisms and for tailoring nanotube features toward different applications.