Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 43: Oxides and Insulators: Adsorption I

O 43.5: Vortrag

Dienstag, 8. März 2016, 15:00–15:15, H6

UHV-IR spectroscopy study of carbon monoxide adsorption on ceria single crystal surfaces — •Chengwu Yang, Alexei Nefedov, Yuemin Wang, and Chrostof Wöll — Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany

Ceria, one of the most easily reducible metal oxides, exhibits extraordinary reactivities in diverse catalytic processes. The importance of this material has triggered numerous experimental and theoretical studies, in particular aiming at elucidating the properties of oxygen vacancies. The studies on bulk single crystal surfaces, however, are still scarce.

On a novel apparatus combining a state-of-the-art FT-IR spectrometer with a dedicated UHV-chamber, we used carbon monoxide (CO) to probe regular sites and oxygen vacancies at surfaces of bulk CeO2(111), CeO2(110), and CeO2(100) single crystals. It was found that the vibrational frequency of C-O stretching mode strongly depends on facet orientations as well as the reduction of ceria surfaces. The assignment of the CO stretch frequency as determined by IR-spectroscopy was supported by ab-initio electronic structure calculations using density functional theory. The obtained results clearly indicate that the application of CO adsorption as a IR-probe is quite suitable for the determination of facet orientations as well as for probing surface oxygen vacancies and allows us to clarify the ambiguous assignments derived from previous powder and thin film data.