Characterization of Nanostructured Titanates Obtained by Alkali Treatment of TiO₂-Anatases with Distinct Crystal Sizes

Abstract

Layered titanate nanotubes (TTNT) with a general formula NaxH2-xTi3O7·nH2O were synthesized by hydrothermally reacting TiO2-anatase with NaOH at 120 °C. Detailed TGA and XRD characterization indicated that the as-synthesized material rich in sodium as an interlayer cation contained intercalated water (n), which was reduced substantially after nearly complete proton exchange (x = ∼0), while the interlayer distance decreased approaching the interlayer distance d200 of H2Ti3O7. Chemical composition and crystal structure of TTNT as well as their dependence on sodium content were not affected by the crystallite size of the starting anatase. On the other hand, TEM examination and N2 adsorption measurements revealed distinct morphology at the nanometer scale and different textural properties depending on the precursor TiO2. Such dependence was rationalized based on a dissolution−recrystallization mechanism.