title: Catalytically Active and Spectator Ce(3+) in Ceria-Supported Metal Catalysts.
abstract: Identification of active species and the rate-determining reaction steps are crucial for optimizing the performance of oxygen-storage materials, which play an important role in catalysts lowering automotive emissions, as electrode materials for fuel cells, and as antioxidants in biomedicine. We demonstrated that active Ce(3+) species in a ceria-supported platinum catalyst during CO oxidation are short-lived and therefore cannot be observed under steady-state conditions. Using time-resolved resonant X-ray emission spectroscopy, we quantitatively correlated the initial rate of Ce(3+) formation under transient conditions to the overall rate of CO oxidation under steady-state conditions and showed that ceria reduction is a kinetically relevant step in CO oxidation, whereas a fraction of Ce(3+) was present as spectators. This approach can be applied to various catalytic processes involving oxygen-storage materials and reducible oxides to distinguish between redox and nonredox catalytic mechanisms.
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland).
authors.forename: René
authors.initials: R
authors.lastname: Kopelent
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland).|Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich (Switzerland).
authors.forename: Jeroen A
authors.initials: JA
authors.lastname: van Bokhoven
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland).|Institute of Physics, Jan Kochanowski University, 25406 Kielce (Poland).
authors.forename: Jakub
authors.initials: J
authors.lastname: Szlachetko
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland).
authors.forename: Jacinta
authors.initials: J
authors.lastname: Edebeli
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich (Switzerland).
authors.forename: Cristina
authors.initials: C
authors.lastname: Paun
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland).
authors.forename: Maarten
authors.initials: M
authors.lastname: Nachtegaal
authors.affiliation: Paul Scherrer Institute, 5232 Villigen (Switzerland). olga.safonova@psi.ch.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Safonova
keywords: CO oxidation; X-ray spectroscopy; ceria; kinetics; time-resolved studies