Surface analysis of supported platinum catalysts-encapsulation model for metal-support interaction: An XPS study

The surface properties of supported platinum catalysts have been investigated using hydrogen chemisorption and XPS. A mixed oxide system, Pt/TiO2-Al2O3 has been compared with titania-supported systems. A metal-support interaction after high temperature reduction (HTR) has been observed in these systems. The chemisorption measurements indicate a weak suppression in hydrogen uptake after HTR for the mixed oxide system. The encapsulation of the metal particles by the reduced support after reduction at 773K has been elucidated based on the difference in the binding energies between oxygen atom and the support metal. This has been found to be more marked for TiO2 prepared from gel and for mixed oxide samples than for the commercial TiO2. The role of the SMSI state in catalytic activity towards reduction of cinnamaldehyde has also been investigated.