STM and XPS study of CeO2(111) reduction by atomic hydrogen

Syed Mohammad Fakruddin Shahed, Tomo Hasegawa, Yasuyuki Sainoo, Yoshihide Watanabe, Noritake Isomura, Atsushi Beniya, Hirohito Hirata, Tadahiro Komeda

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Reduction of CeO2(111)/Ru(0001) surface by atomic hydrogen was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We observed the formation of oxygen vacancy trimers and hydroxyl trimers on the stoichiometric CeO2(111) surface when it was exposed to atomic hydrogen at room temperature. The reaction of an impinging hydrogen atom with a surface oxygen atom yields a hydroxyl species, which diffuse on the surface until stabilized by the formation of OH trimers. The hydrogen atoms were located at atop sites of the oxygen atoms in the topmost surface layer. A reaction between the hopping hydrogen atom and the hydroxyl species yields a water molecule, which is desorbed from the surface leaving an oxygen defect. The oxygen vacancies were also observed as a trimer of vacancies. XPS measurements showed an increase of a reduced Ce and hydroxyl species with an amount of exposed hydrogen atoms. The former was estimated by measuring the ratio of Ce3 +/Ce4 + in the Ce 3d components. Our study shows the formation of hydroxyl trimer species in atomic scale upon atomic hydrogen exposure to CeO2(111) surface which could offer new catalytic activity.

Original languageEnglish
Pages (from-to)30-35
Number of pages6
JournalSurface Science
Volume628
DOIs
Publication statusPublished - 2014 Oct

Keywords

  • Metal oxide surface
  • Oxide catalysis
  • Reduction
  • Scanning tunneling microscope
  • X-ray photoelectron spectroscopy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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