title: Introducing Time Resolution to Detect Ce3+Catalytically Active Sites at the Pt/CeO2Interface through Ambient Pressure X-ray Photoelectron Spectroscopy.
abstract: X-ray photoelectron spectroscopy has been employed for the qualitative and quantitative characterization of both model and real catalytic surfaces. Recent progress in the detection of photoelectrons has enabled the acquisition of spectra at pressures up to a few tens of millibars. Although reducing the pressure gap represents a remarkable advantage for catalysis, active sites may be short-lived or hidden in the majority of spectator species. Time-resolved experiments, conducted under transient conditions, are a suitable strategy for discriminating between active sites and spectators. In the present work, we characterized the surface of a Pt/CeO2powder catalyst at 1.0 mbar of a reacting mixture of carbon monoxide and oxygen and, by means of time resolution, identified short-lived active species. We replaced oxygen with nitrogen in the reaction mixture while fast-detecting the core level peaks of cerium. The results indicate that active Ce3+sites form transiently at the surface when the oxygen is switched off. Analysis of the depth profile shows that Ce3+ions are located at the ceria surface. The same experiment, performed on platinum-free ceria, reveals negligible reduction, indicating that platinum boosts the formation of Ce3+active sites at the interface.
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: Luca
authors.identifier: http://orcid.org/0000-0003-4683-6447
authors.initials: L
authors.lastname: Artiglia
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Orlando
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich , CH-8093 Zurich, Switzerland.
authors.forename: Kanak
authors.initials: K
authors.lastname: Roy
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: René
authors.initials: R
authors.lastname: Kopelent
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: Olga
authors.initials: O
authors.lastname: Safonova
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: Maarten
authors.initials: M
authors.lastname: Nachtegaal
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Huthwelker
authors.affiliation: Paul Scherrer Institute , CH-5232 Villigen, Switzerland.|Institute for Chemical and Bioengineering, ETH Zurich , CH-8093 Zurich, Switzerland.
authors.forename: Jeroen A
authors.initials: JA
authors.lastname: van Bokhoven