Experimental data on synthesis and characterization of WO3/TiO2 as catalyst

WO3/TiO2 is a composite photocatalyst that is being widely used in heterogeneous photocatalysis because it presents better photocatalytic properties than TiO2. For example, the probability of recombination of the electron/hole pairs is diminished and a more range of the solar spectrum is used for its excitation. However, this depend of variables such as tungsten oxide concentration, calcination temperature and synthesis method. This work is focused in establish the effect of WO3 on the morphological and structural characteristics of TiO2. WO3/TiO2 was synthesized by sol-gel method at different calcination temperatures and at different concentrations of tungsten oxide. The surface area, the possible transition between valence band and conduction band, particle size, elemental analysis and crystallography were examined through the BET, DRS, SEM-EDS and XRD analysis.

a b s t r a c t WO 3 /TiO 2 is a composite photocatalyst that is being widely used in heterogeneous photocatalysis because it presents better photocatalytic properties than TiO 2 . For example, the probability of recombination of the electron/hole pairs is diminished and a more range of the solar spectrum is used for its excitation. However, this depend of variables such as tungsten oxide concentration, calcination temperature and synthesis method. This work is focused in establish the effect of WO 3 on the morphological and structural characteristics of TiO 2 . WO 3 /TiO 2 was synthesized by sol-gel method at different calcination temperatures and at different concentrations of tungsten oxide. The surface area, the possible transition between valence band and conduction band, particle size, elemental analysis and crystallography were examined through the BET, DRS, SEM-EDS and XRD analysis.

Data
Doping TiO 2 pretend to improve its photocatalytic performance, since even though it presents a great effectiveness in the degradation of recalcitrant compounds only it achieves its excite state by absorption UV energy, which correspond to 5% of solar spectrum. So more than 50% of visible radiation is being wasted [2,3]. Therefore, it is necessary the coupling of this catalyst with another compound or mixed oxides and characterize the properties of the new materials product of doping. In this case WO 3 / TiO 2 . Some physicochemical properties of titanium oxide and tungsten oxide are shown in Table 1.

Experimental design, materials and methods
Calcination temperature directly affects the crystalline structure of TiO 2 . It was found that anatase phase presents a better photocatalytic performance than rutile phase [4], so in this work three calcination temperatures 500, 600 and 700 C were evaluated. Another parameter for improving the photocatalytic activity of TiO 2 is the doping percentage by weight of WO 3 , which favor the shift in the energy absorption toward visible light region. In this case it was varied in 1, 3 and 5% w/w.

Characterization
Surface area of the photocatalyst obtained was determined by nitrogen physisorption onto material surface using the Brunauer, Emmett and Teller (BET) theory. The Kubelka-Munk function was used for estimating the Eg based on the reflectance spectroscopy values [1]. The surface area and band gap of the synthesized photocatalyst to different conditions are shown in Table 2 and Table 3 Value of data Data obtained allow knowing the calcination temperature effect and the percentage by weight of WO3 in the crystalline structure of the synthesized photocatalyst. It can be observed that the addition of WO3 allows that anatase phase of TiO2 be more thermally stable which could contribute to the improvement of photocatalytic activity of WO3/TiO2. The bang gap data for each sample of photocatalyst at different percentage by weight of WO3 and calcination temperature were obtained, which could serve as references for improving the doping with another oxide. Data may be useful for future research.
In order to know the morphology and composition WO 3 /TiO 2 photocatalyst samples, SEM and EDS analyzes were performed. The results are shown in Fig. 1 and Table 4 respectively.
XRD analysis was performed on samples calcined at 600 C (Fig. 2.) and 700 C (Fig. 3.) because at these temperatures the crystalline transition is achieved. JCPDS 21e1272 and JCPDS 21e1276 cards were used as patterns for the anatase phase and the rutile phase respectively.
The Fig. 4 shows the relationship between the Anatasa and Rutile phase on different catalysts synthesized.