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 conditions. The Pt-TiO2 samples gave an homogeneous nanometric metal dispersion after drying heat treatment forming platinum particles in the range 2–4 nm. All the samples have been characterised using several techniques, namely thermogravimetric analysis, gas-chromatography, mass spectrometry, thermogravimetric analysis combined with mass spectrometry or with gas chromatography/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-nitrophenol photodegradation in aqueous suspension used as a “probe” reaction. Characterisation results indicate that the thermal and chemical treatments 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 preparation procedure of the catalyst particles interferes negatively in the kinetics of the photocatalytic process.