The Preperation Of TiO₂,W⁶⁺/TiO₂ Nanotubes And Photocatalytic Degradation Of Toluene In Gas-phase

In this paper, TiO2 nano-particles were prepared firstly by sol-gel method with the tetrabutyl titanate as main materials, then TiO2 nanotubes were synthesised via hydrothermal method by those nano-particles. Moreover, W6+/TiO2 nanotubes were prepared by the different methods of sol-gel and precipitation-impregnation.The properties of these catalysts were characterized by X-Ray diffraction (XRD), surface area measurement (BET), transmission electron microscopy (TEM), UV–vis adsorption spectra and Fourier transform infrared spectroscopy (FTIR) techniques. The photocatalytic activity of the as-prepared samples was evaluated by the degradation of toluene in gas-phase. The effects of calcined temperature, doping methods and doping concertration on the crystal, structure, morphologies and photocatalytic activity of the TiO2 nanotubes were discussed.The results showed that the crystal structure of the nanotubes was composed of H2Ti2O5·H2O and anatase TiO2. The H2Ti2O5·H2O was translated to TiO2 after calcined. The anatase was translated to rutile and the surface area was decreased as the increasing of the calcined temperature. The optimal calcined temperature for the photocatalytic activity was 450℃. In addition, the nanotube samples without calcined shew a higher photocatalytic oxidization rate than TiO2 nanotubes calcinled at 450℃in the first 120 min, which can be attributed to its anatase crystal structure and large surface area.In the sol-gel pepared W6+/TiO2 nanotubes, the W6+ substituted Ti4+ into the TiO2 crystal lattice, the nanotube structure was optimized and the surface area was enlarged. But in the precipitation-impregnation prepared W6+/TiO2 nanotubes, the W6+ clothed over the TiO2 nanotubes physically without changing the crystal structure and the surface area decreased as the increasing of the W6+ doping. The adsorption of the photocatalyst for OH- and H2O was enhanced and the light response range of the photocatalyst was extended in both of the methods.It can be known from the research that W6+ doping could improve the photocatalytic activity of TiO2 nanotubes significantly. The photocatalytic activity of W6+/TiO2 nanotubes was both related to the doping quantity and the preparation methods. In all of these nanotubes, the sol-gel pepared W6+/TiO2 nanotubes with x(W)=1% owned the best photocatalytic activity. The photocatalytic mechanism of W6+/TiO2 and the pathway of toluene degration in gas-phase systerm were also discussed according to some references.