Relation between phase composition and photocatalytic activity of TiO2 in a sulfoxide deoxygenation reaction

In the present study we synthesize three TiO2 samples, TiO2-500, TiO2-750 and TiO2-850, by a sol-gel procedure varying the rutile and anatase content by calcination at different temperatures. Characterization by XRD, NIR-Raman, UV-Raman, BET, DR-UV-Vis spectroscopy and SEM points out that TiO2-500 consists mainly of anatase and TiO2-850 of rutile. TiO2-700 presents both phases on the surface that is the part of the photocatalyst interested by UV illumination. The photocatalysts are tested in the deoxygenation reaction of methyl p-tolyl sulfoxide to the corresponding sulfide using 2-propanol as hole scavenger. It is demonstrated that the presence of both anatase and rutile on the surface of TiO2-700 is responsible of the increase of the photocatalytic activity. This is likely due to a more efficient charge separation process that increases lifetime of the charges giving availability of electrons and holes for the photocatalytic reaction. Methyl p-tolyl sulfide is formed with a selectivity of 100%.