Microwave assisted synthesis of mesoporous titania

Titanium dioxide, TiO2, is a very versatile and cheap material that can be used in a lot of different applications like (photo)catalysis, sensing and self cleaning coatings.1 Many of these applications take advantage of a high specific surface area and a high degree of crystallinity. As there is always the trade-off between these two parameters, obtaining both in the same material is not straightforward. By using microwave irradiation we were able to achieve this goal. A highly mesoporous titania material with a specific surface area above 330 m²/g,which is among the highest numbers presented in literature, was obtained by adding an additional microwave irradiation step during a normal evaporation-induced self-assembly (EISA) synthesis. The degree of crystallinity which is often neglected in literature, was determined using Rietveld refinement and an increased degree of crystallinity with more than 10 % was achieved. The isoelectric point, particle size and surface groups remained the same after the addition of a microwave irradiation step to the synthesis, thus retaining the material properties that are crucial for applications. One step further in obtaining outstanding materials is the addition of noble metal nanoparticles on mesoporous titania. This kind of materials has a lot of applications in the (photo)catalyst sector. Many synthesis routes are already developped to prepare these kind of materials, but little is known about the oxidation state of the metal ions present in these materials even though it can be an important factor when one studies the reaction mechanisms of a reaction. Therefore we performed a study of the oxidation state of gold atoms of Au/TiO2 materials reduced in four different ways, using X-ray adsorption spectroscopy (XAS).2 We found that different particle sizes, oxidation states and interactions of the gold with the titania support are obtained when one uses different reduction methods. When one uses these composite materials in photocatalytic remediation reactions or alcohol oxidation reactions, one can observe differeneces between these samples even though the gold loading stays the same. REFERENCES 1. M. Arin, P. Lommens, et al., J. Eur. Ceram. Soc., 2011, 31, 1067-1074. 2. M. Meire, P. Tack, et al., Spectrochim. Acta B, 2015, 110, 45-50