Morphology control of TiO2 through hydrothermal synthesis method using protonic tetratitanate

Fibrous TiO2 and plate-like TiO2 were obtained through the hydrothermal synthesis method by using two kinds of protonic tetratitanate (H2Ti4O9), prepared by ion exchange of K2Ti4O9 and HCl, or milled K2Ti4O9 and HCl, respectively. The product made by hydrothermal treatment of H2Ti4O9 without milling in water consisted of anatase TiO2 and retained the fibrous morphology of the precursor but with fine crystals attached on the surface, formed by the in situ topotactic transformation reaction and dissolution and recrystallization. On the other hand, TiO2 prepared with H2Ti4O9 obtained through ion exchange of milled K2Ti4O9 and HCl had plate-like shape, namely retaining the morphology of nanosheets of H2Ti4O9 through an in situ transformation process. Under ultraviolet irradiation, 70% methyl orange degradation by TiO2 nanosheets was about 3.3 times higher than that by fibrous TiO2. The higher surface area, higher pore volume, and smaller particle size led to the higher photocatalytic activity of the TiO2 nanosheets.