Photocatalytic Efficiency of TiO2/Fe2O3 and TiO2/WO3 Nanocomposites

The photocatalytic proprieties of TiO2/FeO3 and TiO2/WO3 nanocomposites have been investigated using methylene blue as a pollutant. We propose a non-conventional approach for material preparation, i.e., the Doctor Blade technique, which is an easy and inexpensive method for coating materials. Several drawbacks related to the use of powders can be alleviated by using solid substrates, and this deposition method allows us to take advantage of the high surface area of nanoparticles, avoiding dispersion in the solution. The possibility of coating a material with a photoactive molecule with an easy and inexpensive method leads to the use of photocatalysis in the real world. The structural, optical, and textural characterizations of these materials were carried out using UV-vis. Diffuse Reflectance Spectroscopy (DRS) was used to calculate the energy band gap with the Kubelka-Munk method, and N-2 absorption-desorption measurements were used to study the exposed surface area (S-BET). The photocatalytic activity was evaluated in nanocomposites containing 0.1/0.2/0.3/0.5 wt.% of Fe2O3 or WO3 or both Fe2O3 and WO3. An enhancement of about 60% was achieved by adding 0.2% wt. of WO3 after 2 h of exposure to UV light. The TiO2@Fe2O3 and TiO2@WO3/Fe2O3 mixtures showed the same behavior as the TiO2@WO3 mixture. Therefore, the photoactivity of these photocatalysts is not related to the oxide itself. These solid results are due to the energy band structure of the materials. In fact, there is an important band matching among TiO2, WO3, and Fe2O3, which gives these nanocomposites a substantial improvement in photodegradation. The pH evaluated was neutral pH both at the beginning and at the end of the experiment, which is consistent with the well-known photodegradation pathway of methylene blue.