Ceria nanoformations in CO oxidation on Pt(111): Promotional effects and reversible redox behaviour

A well-defined CeOx/Pt(111) model catalytic system has been fabricated using the self-assembling of Ce adatoms on a Pt(111) surface with a subsequent oxidation of the nucleating Ce submonolayer (0.3 ML). The resulting system of the ‘‘inverse supported catalyst’’ type consists of CeOx nanoformations (2D islands of 5–15 nm size and 0.3 nm in height) more or less uniformly distributed over the Pt(111) surface. This CeOx/Pt(111) system has been tested in the CO oxidation reaction where both the CO2 production rate and the Ce oxidation state were monitored in situ. An enhanced reactivity and a remarkable shift of the bistable region of the reaction towards higher CO pressures were observed when compared to a clean Pt(111) surface. The CeOx islands exhibit a pronounced redox behaviour that follows the hysteresis cycle of the reaction. The usefulness of such a type of the ‘‘inverse model catalyst’’ for studying the oxygen diffusion supply and the redox behaviour of ceria in the ceria-platinum catalysts is demonstrated. 2007 Elsevier B.V. All rights reserved.