Abstract
Adsorption of hydrogen and carbon monoxide at the surface of anatase-supported platinum was studied by heat-flow calorimetry. When strong metal-support interaction (SMSI) is created by high-temperature (773 K) reduction of the sample in hydrogen, the metal area available for adsorption decreases to 10% of the total area initially present in the sample. However, the reactivity of the remaining metal surface, with respect to either carbon monoxide or hydrogen at 296 K, is similar to the reactivity of normal platinum. These results may be considered as indirect evidence for encapsulation (or decoration) of the metal by the reduced support. The small but significant decrease of the initial heat of adsorption of hydrogen following the development of SMSI indicates that the reduced support modifies the chemical properties of the surface metal atoms. Oxygen interacts at 296 K with the high-temperature pretreated Pt TiO 2 sample and almost completely suppresses SMSI. The heat of regeneration is identical to the heat of reoxidation of titanium oxide (anatase), pretreated in the same conditions as the Pt TiO 2 sample. It is close, in absolute value, to the heat of formation of anionic vacancies in the TiO 2 lattice, calculated from equilibrium measurements of electrical conductivity.
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