Effect of the electrolyte chemical nature on the formation and characteristics of TiO2 nanotubes synthesized by anodic oxidation using a Ti cathode

Abstract

The aim of this work is to show the effect of the electrolyte chemical nature on the formation of self-organized TiO 2 nanotubes (TNT) arrays synthesized via anodic oxidation, when using a Ti cathode. The synthesis was performed in situ in a potentiostatic cell provided with an anode and a cathode (both Ti substrates pretreated) under constant hydrodynamic conditions and different anodizing times, temperatures and electrical potentials. Ti electrodes were immersed in 300 mL of each of an inorganic and organic electrolyte. Then, a thermal treatment varying the temperature and the heating rate in each case was applied to convert the amorphous TiO 2 to crystalline TiO 2. TNT were characterized by field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and atomic force microscopy (AFM). FESEM showed the formation of nanotubular structures perpendicular to Ti substrate with average inner diameters of 84 and 57 nm for TNT synthesized in the electrolytes with different nature tested (inorganic and organic), and labeled hereafter as TNT-I and TNT-O, respectively. EDS spectra from different zones of the substrate confirmed the presence of Ti (~ 34.2%) and O (~ 66%) on the surface of the TNT. The anatase (~ 86%) and rutile (~ 14%) crystalline phases were detected via XRD in both cases. AFM provided information about the topographic profile of TNT and the roughness of the substrates. Thus, the use of a semiconductor cathode allowed the successful synthesis of the TNT and the electrolyte chemical nature was found to influence its morphology, dimensions and formation mechanism.