Influence of the structural characteristics of Ti1−xSnxO2 nanoparticles on their photocatalytic activity for the elimination of methylcyclohexane vapors

In the present work, we have used Ph3SnOH as precursor for the synthesis of highly active Ti1−xSnxO2 nanosized photocatalysts. This new preparation route is based on the reaction of TiCl4 with the organometallic compound in an organic medium to yield an amorphous precipitate of TiO2 which contains adsorbed tin species. Subsequent crystallisation of the precipitate under thermal or hydrothermal conditions determines the phase composition (rutile/anatase ratio) and the particle size of the final material. Characterisation data reveal that the incorporation of Sn promotes the anatase to rutile transformation but reduces the size of rutile crystallites. The activity of these samples has been tested for the photocatalytic oxidation of methylcyclohexane (MCH) vapors in an oxygen flow. This hydrocarbon can be considered representative of the volatile organic chemicals (VOC) present in urban atmospheres. The results obtained indicate that the Ti1−xSnxO2 materials obtained under thermal conditions present higher specific photoactivity than the reference material TiO2 P25, especially when the reaction is performed in a stream of humid oxygen. On the other hand, the comparison with undoped TiO2 prepared in similar conditions shows that the incorporation of Sn significantly increases the photocatalytic oxidation rate. High crystallinity and an adequate anatase to rutile ratio seem to be beneficial for the removal of MCH. In contrast, pure rutile Ti1−xSnxO2 nanoparticles prepared by autoclaving the amorphous precursor in HCl shows a quite limited photoactivity, despite its high surface area.