Effects of the modification with tungstosilicic acid on the physicochemical properties of mesoporous titania

VANESA M. FUCHS, LUIS R. PIZZIO , MIRTA N. BLANCO

San Franciso

Encuentro; 21 st North American Catalysis Society Meeting; 2009

TiO2 (titania) is considered as one of the most appropriate semiconductor materialsto be employed as a photocatalyst, due to its high activity in the photodegradation of organiccompounds, its low cost, low toxicity, and chemical stability [1-2]. The photocatalytic activityof titania is influenced by the crystalline structure, the specific surface area, the porosity, theparticle size and the size distribution, the band gap (Eg), and the surface density of hydroxylgroups, among other factors [3]. The low specific surface area and the fast recombination ofelectrons and holes are considered as being mainly responsible for the low photocatalyticefficiency displayed by TiO2 in practical applications.Titania with large surface area was reported to be suitable to obtain high catalytic performanceand can be synthesized using urea as a low cost template via sol-gel reactions [4].The photocatalytic activity of TiO2 based catalysts can be improved by the separation of theelectrons and holes and the increase of the surface area. It is known that doping with suitablemetal ions allows extending the light absorption of large band-gap semiconductors to thevisible region [5]. Tungstophosphoric acid, a heteropolyacid (HPA) with Keggin structure, hasbeen used to modify TiO2 in order to reduce the charge recombination. It has been incorporatedinto TiO2 colloids [6] or introduced into titania matrix [7]. In addition, the incorporation ofHPA into titania matrix can improve the density of the catalysts and make easier theirseparation from heterogeneous reaction systems for re-use.Going on with our previous work, as the addition of tungstosilicic acid (TSA) to titania wasscarcely studied, we present here the preparation and characterization of TSA-modifiedmesoporous titania obtained using urea as low cost template, via HCl catalyzed sol-gel reaction