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 K ₂Ti₄O₉ 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 H ₂Ti₄O₉ obtained through ion exchange of milled K₂Ti₄O₉ and HCl had plate-like shape, namely retaining the morphology of nanosheets of H₂Ti₄O ₉ 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.