Synthesis of photocatalytic active fibrous titania by the solvothermal reactions

Abstract

Fibrous titania was synthesized by the solvothermal reactions of H₁Ti₄O₉ nH₂in different media. H₂Ti₄O₉·nH₂O transformed in steps to H₂Ti₈O₁₇, monoclinic TiO_z, anatase and rutile. The phase transformation temperature and microstructure of the products changed significantly depending on the heating environment. The critical temperature at which anatase appeared in liquid media was much lower than that in air. The titania fibers consisted of nanocrystals of TiO₂. The crystallite size and crystallinity of titania decreased with decreasing the dielectric constant of the reaction medium. Consequently, the photocatalytic activity of titania changed with heat treatment media in the following sequence: ethanol, methanol > water > air, i.e., fibrous titania possessing excellent photocatalytic activity could be obtained by the solvothermal reactions using alcohol such as methanol and ethanol. Titania powders crystallized by the solvothermal reaction in methanol also possessed excellent thermal stability.