Study On The Composition,Structure And Photocatalytic Activity Of Titanate Nanotubular By Hydrothermal Method

Nanotubular titanates, with an external diameter around 10 nm were prepared by hydrothermal processing using commercial anatase-type TiO₂ powder as raw material in the NaOH (aq.) solution. The samples obtained at different conditions were characterized by means of TEM,XRD and EDS. The thermal stability and photocatalytic activity of the titanate nanotubes were investigated. The results are as following:Nanotubular titanate formed during hydrothermal treatment rather than in washing or immersing processes. NaxH2-xTi307 or mixtures of Na_xH_2-xTi₃O₇ and TiO₂ nanotubes can be obtained by control the pH values of immersing solutions. The nanotubular titanate are stable with original symmetry crystal structure till 400℃and keeps nanotubular under 500℃. At higher heat-treatment temperatures, the anatase structure will change into rutile structure and a new Na₂Ti₆O₁₃ crystal obtained by the reaction of rutile-type TiO₂ with Na₂Ti₃O₇. At 800℃, the main crystal Na₂Ti₆O₁₃ and small quantity of rutile TiO₂ is found in the sample.It is also found that the crystal structure and photocatalytic activity of the titanate nanotubes strongly depend on the calcination temperature. Both of the noncalcined nanotubes and the calcined nanotubes at 400℃show a low photocatalytic activity. When the calcination temperature reaches 500℃, the calcined nanotubes show a higher photocatalytic activity. However, with the increasing of calcination temperature, the photocatalytic activity of the calcined samples decreases, because the anatase structure transforms into rutile structure and a new Na₂Ti₆O₁₃ crystal.