Sol-gel synthesis and characterisation of TiO2-anatase powders containing nanometric platinum particles employed as catalysts for 4-nitrophenol photodegradation

A set of TiO2 and Pt-TiO2 polycrystalline samples were prepared by sol-gel method hydrolysing a modified alkoxide titanium precursors under acidic con ditions. The Pt-TiO2 samples gave an homogeneous nanometric metal dispersio n after drying heat treatment forming platinum particles in the range 2-4 n m. All the samples have been characterised using several techniques, namely thermogravimetric analysis, gas-chromatography, mass spectrometry, thermog ravimetric analysis combined with mass spectrometry or with gas chromatogra phy/mass spectrometry, X-ray diffraction coupled with a Rietveld refinement procedure, X-ray photoelectron spectroscopy and determination of specific surface area. Moreover, the samples have been employed as catalysts for 4-n itrophenol photodegradation in aqueous suspension used as a "probe" reactio n. Characterisation results indicate that the thermal and chemical treatmen ts of the catalysts influenced the photocatalytic activity. In the Pt-TiO2 samples both Pt(0) and Pt(II) species are present in the catalyst particles and the most abundant phase is anatase for all of the samples. Doping with Pt beneficially influences the photo-oxidant properties of TiO2 while the presence of organic residual species on the surface, deriving from the prep aration procedure of the catalyst particles interferes negatively in the ki netics of the photocatalytic process.