| Abstract
| - TiO2 (commercial-P25 and synthesized by sol−gel method) was surface modified with platinum ions or[Pt3(CO)6]62- clusters to improve its photocatalytic activity. The physical properties of the synthesizedphotocatalysts were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), andBrunauer, Emmett and Teller adsorption (BET) methods. To characterize the absorption ability of visiblelight, the diffusion reflectance spectra (DRS) were recorded. The charge-carrier lifetimes in TiO2 after UVillumination were determined by microwave absorption experiments using the time-resolved microwaveconductivity (TRMC) method. The photocatalyst activity was examined by degradation of exemplary aqueousphase pollutants, such as Rhodamine B and phenol. The impact of the adsorbates on the photocatalytic activitydepends strongly on the titania precursor (commercial or synthesized), the irradiation wavelength (UV orvisible), and the model compound (dye or phenol). The results show that it is possible to enhance the P25photocatalytic activity under UV−visible light by doping it with Pt clusters. Also, P25 doping with Pt(II) orPt clusters results in enhancement of the activity under visible light. Pt(IV)/TiO2 synthesized by sol−gelmethod exhibits better photoactivity under UV−visible and visible light compared to the unmodified titania.In all mentioned systems, a positive effect of modification with platinum clusters and, in particular, an importantenhancement in photocatalytic activity under visible light were obtained. These results are explained byenhancement in visible light absorption and inhibition of charge-carrier recombination.
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