The photocatalytic activity of sol–gel derived photo-platinized TiO2 films

Sol–gel TiO2 thin films have been loaded with platinum clusters through a photo-platinization method using water/ethanol platinum solutions. The morphological and physico-chemical properties of platinized films as well as the chemical state of platinum clusters have been studied by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. These characterizations show that morphological and physico-chemical properties are strongly influenced by the water/ethanol composition of the platinum solution and temperature of the post-platinization heat-treatment, which in turn determines the photocatalytic performances of platinized films. UV-assisted photocatalytic reactions induced by platinized films follow bi-regime kinetics. The first regime is characterized by a rather high rate constant, while long term UV exposition promotes a more or less pronounced deceleration of the photocatalytic reaction. Optimization of the photocatalytic activity requires a platinization in presence of a water excess followed by a heat-treatment in the 250–400 °C thermal range. Films processed in such conditions exhibit rate constants in the first and second photocatalysis regime which are four times and three times greater, respectively, than the rate constant measured for non-platinized films.