Understanding the mechanism of TiO2 nanotubes formation at low potentials (≤ 8 V) through electrochemical methods

The electrochemical characterization of cpTi-2 during anodization was carried out to understand the formation of nano-tubular structure at different applied potentials (<= 8 V). The linear sweep voltammetry, potentiostatic polarization and impedance spectra analyses were conducted to estimate the possible reaction sequence during anodization in fluoride and phosphate containing electrolyte. Effect of applied potential on the surface morphology was examined under scanning electron microscope. The generation of Lewis acid active sites within the pre-formed passive film beyond the critical potential (>= 1.9 V vs. SCE) would enhance the growth of oxide film with simultaneous localized dissolution by the formation of [TiF6](2-) complex. It has been evaluated that the competitive field assisted oxidation and field enhanced dissolution processes at the surface would result in the formation of nano-tubular morphology at the surface of Ti.