Mesoporous Pt-TiO2 thin films: Photocatalytic efficiency under UV and visible light

• Preparation of mesoporous Pt-doped titania thin film by EISA process.
• Characterization of the Pt oxidation state at the surface of the films.
• Comparison of the UV and visible photocatalytic activity of doped/undoped films.
• Quantification of hydroxyl radicals production at the films surface.

The preparation, characterization, and photoactivity of mesoporous Pt-TiO2 thin films were investigated. Titania based thin films were prepared by evaporation induced self assembly (EISA) process, Pt being introduced by a non-photochemical process via two different ways. Whatever the synthesis method and the Pt content (between 0.5% and 3%), the prepared films were thin (around 200 nm) and mesoporous with an average pore size of 5 nm. XPS surface analysis showed that Pt was present in different oxidation states: mainly Pt0 but also Pt2+ and Pt4+. The presence of Pt0 nanoparticles was also clearly evidenced by Transmission Electronic Microscopy. The photocatalytic efficiency of the mesoporous titania films was determined by two different tests under both UV and visible light: the reaction rates and photonic efficiencies were determined for the mineralization of stearic acid (SA) at the gas–solid interface and for the solid–liquid photobleaching of Methylene Blue (MB). In all the cases, Pt-doped titania films were less active than pure TiO2 films under UV light and slightly more active under visible light. Preliminary results on the HO production on the surface of the films were obtained from the reaction of a specific probe (terephtalic acid, TA) in basic aqueous solutions. These results were discussed relative to literature data.

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