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Surface Science Spectra / Volume 11 / Issue 1

Surf. Sci. Spectra 11, 73 (2004); http://dx.doi.org/10.1116/11.20050201 (9 pages)

X-ray Photoelectron Spectroscopy Studies of Oxidized and Reduced CeO2(111) Surfaces

Mark Engelhard1, Samina Azad2, C.H.F. Peden2, and S. Thevuthasan3

1PNNL, Environmental Molecular Sciences Laboratory, 3335 Q Avenue, Richland, Washington 99352
2PNNL, Chemical Sciences Division, 3335 Q Avenue, Richland, Washington 99352
3PNNL, Environmental Molecular Sciences Laboratory, 3335 Q Ave, Richland, Washington 99352

(Published online 28 November 2005)

We have studied the electronic structure of oxidized and reduced CeO2(111) surfaces using x-ray photoelectron spectroscopy (XPS). The 50 nm thick CeO2(111) film was grown on a YSZ(111) substrate using oxygen plasma assisted molecular beam epitaxy (OPA-MBE). This film has been characterized using in situ (RHEED) reflection high energy electron diffraction and ex situ x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Rutherford backscattering spectroscopy (RBS). The lattice mismatch between CeO2(111) and YSZ(111) is less than 5% and yields a flat surface that is comprised of an equivalent number of Ce4+ and O2− ions. Oxidation with O2 at 773 K under UHV conditions was sufficient to fully oxidize the CeO2(111). Surface reduction was carried out by annealing in UHV at 973 K. Ceria is a technologically important metal oxide with many interesting catalytic properties. The most common use of ceria is in the treatement of automobile exhaust gases, primarily due to its oxygen strorage capacity (OSC), which allows reduction of NO as well as oxidation of CO in the catalytic converter. In a reducing atmosphere cerium ions shift from Ce4+ to Ce3+ whereas under oxidizing conditions they shift from Ce3+ to Ce4+, and the charge compensation is facilitated by oxygen vacancies that are produced on the reduced surface. In this study we have have used x-ray photoelectron spectroscopy (XPS) to investigate the electronic states of in situ oxidized and reduced CeO2(111). © 2005 American Vacuum Society.

© 2005 American Vacuum Society

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KEYWORDS and PACS

Keywords

X-ray photoelectron spectra, oxidation, reduction (chemical), cerium compounds, thin films, reflection high energy electron diffraction, X-ray diffraction, transmission electron microscopy, Rutherford backscattering, annealing, catalysis, catalysts, vacancies (crystal), surface states, CeO2(111), XPS, oxidized, reduced, x-ray photoelectron spectroscopy, CeO2

PACS

  • 79.60.Bm

    Clean metal, semiconductor, and insulator surfaces

  • 81.65.Mq

    Oxidation

  • 68.37.Lp

    Transmission electron microscopy (TEM)

  • 68.49.Sf

    Ion scattering from surfaces (charge transfer, sputtering, SIMS)

  • 81.40.Gh

    Other heat and thermomechanical treatments

  • 82.45.Jn

    Surface structure, reactivity and catalysis

  • 82.65.+r

    Surface and interface chemistry; heterogeneous catalysis at surfaces

  • 61.72.J-

    Point defects and defect clusters

  • 73.20.-r

    Electron states at surfaces and interfaces

History
Received 28 February 2005
Accepted 2 August 2005
Published online 28 November 2005
Digital Object Identifier
http://dx.doi.org/10.1116/11.20050201

PUBLICATION DATA

ISSN

1055-5269 (print)  
1520-8575 (online)

Publisher

American Vacuum Society

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