The strong metal–support interaction (SMSI) in Pt–TiO2 model catalysts. A new CO adsorption state on Pt–Ti atoms

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Abstract
In order to investigate the microscopical aspects of the SMSI state in catalysts we performed photoemission experiments on samples consisting of submonolayer Pt deposits on a Ti(0001) surface and on a TiO2thin film.Annealing Pt/TiO2 samples at ∼500 °C caused a change in the electronic structure of Pt atoms which was reflected in a narrowing of the Pt 4f 7 / 2XPS line. The width of this line became smaller than the corresponding one for a bulk Pt sample. This was interpreted as the result of an electron transfer between Pt and Ti atoms that we designed for brevity as alloying. CO adsorption on alloyed Pt–Ti exhibited in Pt/TiO2 samples an unusual C1s binding energy of 291.3 eV. The uptake of CO per Pt atom in Pt/TiO2 samples was reduced, by a factor of 2 when CO was adsorbed on surfaces previously annealed at 500 °C which is the temperature for the SMSI state in Pt/TiO2 catalysts.