A New Benchmark for TiO₂ Nanotube Array Growth by Anodization

Abstract

We report on the anodic formation of a self-standing 720 μm thick TiO2 nanotubular membrane by complete consumption of a 250 μm thick titanium foil sample. By employing double sided electrochemical oxidation of titanium in an electrolyte comprised of water, NH4F, and ethylene glycol, we obtain two highly ordered, hexagonal close-packed titania nanotube arrays 360 μm in length that are separated by a thin compact oxide layer; the individual nanotubes in each array have an aspect ratio of ∼2200. The potentiostatic anodization of titanium in an ethylene glycol, NH4F, and water electrolyte dramatically increases the rate of nanotube array growth to approximately 15 μm/h, representing a growth rate ∼750−6000% greater than that seen, respectively, in other polar organic or aqueous based electrolytes previously used to form TiO2 nanotube arrays. We consider the effects of electrolyte composition, applied potential, and anodization duration on the length and diameter of the resulting nanotubes in terms of a growth rate model, with results suggesting that reduced hydroxyl ion injection from the electrolyte, which enables faster high field ionic conduction through the barrier layer, is responsible for the high nanotube growth rates achieved. Furthermore, as reported herein for the first time, we are able to make self-standing TiO2 nanotube array films ranging in thickness from 50 to 360 μm.

Study of Titanium Dioxide Nanotube Array for the Application in Dye-Sensitized Solar Cells

“…1. This high current enhances temperature of the electrolyte which in turn reduces the deposition rate and thickness [16]. The measured reflectance was converted directly to absorbance (log(1/R)) where R represents relative diffuse reflectance.…”

Crystallite phase-controlled preparation, characterisation and photocatalytic properties of titanium dioxide nanoparticles

“…anodising of Ti) [20][21][22], solution combustion method [23][24][25], microemulsion [26,27], micelle and inverse micelle methods [28,29], ball milling [30], a flame by vapour phase [31], sonochemical reactions [32] and plasma evaporation [33,34]. It should be noted that as precursors of nanocrystalline oxide powders, however, inorganic compounds are more economical than alkoxides.…”

TiO2 nanotubes with ultrathin walls for enhanced water splitting

“…7,11,12 To this end, controlling the length and the diameter of TiO 2 nanotubes has shown tremendous positive effects on the performance of the materials in solar energy conversion. [12][13][14] However, the effect of wall thickness was poorly discussed in the literature, despite the fact that it is one of the determinant factors controlling the dynamics of charge carriers, especially in photoelectrochemical water splitting systems. 7,11,14,15 Most of the published articles deal with wall thicknesses that are greater than the diffusion length of charge carriers in titania.…”