engleski

ungsten doped titania porous thin films for photocatalytic purification of water

Nanostructured TiO2 has taken the scientific focus because of the large specific surface area compared to bulk, increased photo-induced reactions, light absorption, photo-generated charge carrier densities, photo-reduction and contact with pollutants in photo-catalysis. TiO2 nanostructures, in general, have drawbacks in photo-catalysis, since their wide band gaps (anatase Eg = 3.2 eV, rutile Eg = 3.0 eV) limit absorbance of the whole solar spectrum and lead to fast recombination of photo-generated electron– hole pairs. Properties of nanostructured TiO2 materials can be improved by doping or decorating with other materials. In this work, TiO2 nanostructures were doped by tungsten with the aim to narrow the band gap of TiO2. A series of transparent thin films (WxTi1-xO2) are obtained by co-sputtering tungsten-titanium in different atomic ratios on FTO glass substrates and then anodizing them in ethylene glycol solution containing 0.6 % NH4F. The morphology and structure of thin films were characterized by SEM, XRD and Raman spectroscopy. Different techniques were used for photo-electrochemical characterization, while photocatalytic activity under solar irradiation was studied using methylene blue as the target pollutant. SEM images (Fig. 1(A)) showed that the WxTi1-xO2 thin films have a nanoporous structure resembling an open honey-comb construction, while EDS results indicated incorporation of tungsten in the crystal lattice of TiO2. XRD results showed that anatase is the dominant crystalline phase (Fig. 1(B)) ; exhibiting major peaks at 25.3° and 38.0° (2θ) which were indexed to the lattice planes of (101) and (004), respectively (ICDD-JCPDS 01-086-1156) [1]. The characteristic Raman bands of anatase were also observed at 146, 397, 513 and 634 cm-1 (Fig. 1(C)) which can be assigned to Eg, B1g, doublet of A1g+B1g and Eg modes of the anatase phase, respectively [2]. The incorporation of W slightly decreased the band gap of WxTi1-xO2. The thin film with 1 % W showed the maximum photocurrent. Photoelectrochemical results also revealed that the charge recombination decreased with increasing the amount of W. Photocatalytic activity was evaluated by degradation of methylene blue solution at different pH, in which higher pH showed enhanced removal rate. The obtained functional properties will be discussed in the view of structural study.

WxTi1-xO2 ; magnetron co-sputtering ; photoelectrochemical ; photocatalyst ; water treatment

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