Abstract

Model Pt-ceria catalysts have been prepared by the evaporation of Pt onto ceria (CeO2) films grown on Si(1 1 1) substrates. Photoelectron spectroscopy (XPS, UPS) data are, used to characterise the surfaces and their adsorption characteristics, and CO oxidation has been used as a probe reaction to test the activity of the model catalysts. Pure ceria is catalytically-inactive under the test conditions employed, whereas the model Pt/ceria catalysts demonstrate high activity for CO oxidation. The model catalysts also reproduce many of the characteristics of their high-surface area analogues, including the possession of a characteristic light-off temperature, hysteresis in activity as a function of temperature and a negative-order dependence on the CO partial pressure. Many aspects of the behaviour of these catalysts are shown to be a direct result of the strong adsorption of CO. The sensitivity of the dispersed Pt towards oxidation is also experimentally-demonstrated and the importance of this phenomenon is discussed. (c) 2006 Elsevier B.V. All rights reserved.