Enhancement of the photocatalytic activity of various TiO2 materials by platinisation

In the present work, three commercially available TiO2-catalysts, namely Degussa P25, Sachtleben Hombikat UV100 and Millennium TiONA PC50, were platinised by a photochemical impregnation method in two ratios of platinum deposits (0.5 and I wt.%). The physical characterisation of the new synthesised catalysts was carried out by measurements of the BET-surface area, the light absorption properties and the adsorption of the model compounds. The photocatalytic activities of these samples were determined using three different model compounds: EDTA, 4-chlorophenol (4-CP), and dichloroacetic acid (DCA). While in the case of EDTA its disappearance was studied, total mineralisation was measured for 4-CP and DCA. In all cases, the photocatalytical activity was found to increase with rising amounts of Pt, e.g., the photonic efficiency for DCA degradation increased from 12.2% for pure Hombikat UV100 to 32.1% for Hombikat UV100/0.5 wt.% Pt and to 42.7% for Hombikat UV100/1 wt.% Pt. Promising results were also achieved for the total mineralisation of 4-CP. The photonic efficiency rised from 0. 82% using unmodified PC50 to 1.14% with PC50/0.5 wt.% Pt (zero-order kinetics assumed in all cases). Similar results were obtained with the other new synthesised catalyst samples and for the model compound EDTA. No immediate relationship between the photocatalytic activity of the catalyst samples and their physical properties (surface area, adsorption of pollutants, absorption of light) could be observed.