The role of the synthetic procedure of nano-crystalline TiO2 on the photodegradation of toluene

Because of its stability and nontoxicity TiO2 has been extensively investigated as an efficient photocatalyst for purifying water and air. The use of TiO2 in photocatalytic concrete and paints is very promising and intensively investigated. In recent years a great deal of activity was dedicated, by the authors’ group, to the study of synthetic routes leading to nanocrystalline materials with tailored features, mainly in the case of titania. Sol-gel paths, combined with hydrothermal stages performed either in the presence or in the absence of surfactants, have led to nanocrystalline TiO2 with controlled enrichment in either anatase, brookite or rutile [1-4]. There is ample debate in the literature concerning the actual role played by either of the titania polymorphs with respect to the photocatalytic activity of the material [5]. In this work the authors report on the activity of nanocrystalline titania, prepared by a multi-step sol-gel procedure, with respect to the photodegradation of toluene used as a model compound. Samples with varying surface area and anatase/brookite/rutile content are fully characterized and then tested and their photoactivity is compared with that of the most commonly commercial TiO2 photocatalysts. The photodegradation of toluene is investigated both in aqueous and in gas phase. In the former case the composition of the reacting mixture, in terms of side products, is followed by HPLC and MS-GC and the total mineralization by TOC. In the latter case the reactor is equipped with an online micro-GC. [1] T. Boiadjieva, G. Cappelletti, S. Ardizzone, S. Rondinini, A. Vertova, Phys. Chem. Chem. Phys., 5 (2003) 1689. [2] G. Cappelletti, C. Ricci, S. Ardizzone, C. Parola, A. Anedda, J. Phys. Chem. B., 109 (2005) 4448. [3] C.L. Bianchi, S. Ardizzone, G. Cappelletti, Dekker Encyclopedia of Nanoscience and Nanotechnology Marcel Dekker (New York), 2006, pp. 1-10, DOI: 10.1081/E-ENN-120042107 [4] G.Cappelletti, C.L.Bianchi, S. Ardizzone, Appl. Surf. Sci., 253 (2006) 519-524 [5] J. Krysa, M. Keppert, J. Jirkovsky, V. Stengl, J. Subrt, Mater. Chem. Phys., 86 (2004) 333.