Amorphization of Degussa nanosized TiO2 caused by its modification

Influence of modification with metals Au and Ag, oxides of Fe, Mg and Ce and their combinations on amorphization of widely used commercial nanosized TiO2 (Degussa P25) was studied with SR-XRD and EXAFS methods. These systems were chosen taking into account their potential on catalytic properties for biomass to biodiesel transformation, as it was shown in model reaction of liquid phase n-octanol oxidation as well as low-temperature CO oxidation for cold start of the neutralizers of car exhaust gases. Instability of rutile, the most stable TiO2 phase, in the presence of the additives was found. Application of EXAFS method, rarely used for crystalline structure transfer studies, led to elucidation of this apparent effect, which was explained by higher level of amorphization of rutile than anatase. Literature data indicate that bulky TiO2 doping leads to either increase of rutile/anatase ratio complete inhibition of anatase to rutile transformation. Dissimilar phase composition changes, revealed in this work for modified nanodispersed TiO2, was attributed to size effect.