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%. - Highlights: • TiO₂ samples are synthesized via sol–gel varying the rutile and anatase composition. • TiO₂-700 (calcined at 700 °C) presents both anatase and rutile on the surface. • Efficient charges separation is allowed by the presence of anatase and rutile. • Spatial separation of charges renders TiO₂-700 the most active photocatalyst. • Methyl p-tolyl sulfoxide is transformed in sulfide with 100% selectivity