Morphology control of TiO 2 through hydrothermal synthesis method using protonic tetratitanate

Fibrous TiO 2 and plate-like TiO 2 were obtained through the hydrothermal synthesis method by using two kinds of protonic tetratitanate (H 2 Ti 4 O 9 ), prepared by ion exchange of K 2 Ti 4 O 9 and HCl, or milled K 2 Ti 4 O 9 and HCl, respectively. The product made by hydrothermal treatment of H 2 Ti 4 O 9 without milling in water consisted of anatase TiO 2 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, TiO 2 prepared with H 2 Ti 4 O 9 obtained through ion exchange of milled K 2 Ti 4 O 9 and HCl had plate-like shape, namely retaining the morphology of nanosheets of H 2 Ti 4 O 9 through an in situ transformation process. Under ultraviolet irradiation, 70% methyl orange degradation by TiO 2 nanosheets was about 3.3 times higher than that by fibrous TiO 2 . The higher surface area, higher pore volume, and smaller particle size led to the higher photocatalytic activity of the TiO 2 nanosheets.