Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 117, Issue 32, Pages 16371-16380Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp400486r
Keywords
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Funding
- Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-AC02-76SF00515]
- Swedish Research Council (VR)
- Ministry of Education, Culture, Sports, Science and Technology [2009B1751/BL-47XU]
- U.S. Department of Energy [DE-AC02-76SF00515]
- Alexander von Humboldt Foundation
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The electronic structure and stability of Cu(111)-hosted Pt overlayers with and without the presence of atomic oxygen have been studied by means of core-level spectroscopy and density functional theory (DFT). Because of lattice mismatch, Pt(111) overlayers grown on Cu(111) are compressively strained, and hard X-ray photoelectron spectroscopy together with Pt L-3-edge X-ray absorption spectroscopy (XAS) reveals a pronounced downshift of the Pt d-band owing to the increased overlap of the d-orbitals, an effect also reproduced theoretically. Exposure to oxygen severely alters the surface composition; the O-Cu binding energy largely exceeds that of O-Pt, and DFT calculations predict surface segregation of Cu atoms. Comparing the adsorbate electronic structure for O on unstrained Pt(111) with that of O on Pt-modified Cu(111) using O K-edge XAS and X-ray emission spectroscopy salient differences are observed and calculations show that Cu-segregation to the topmost layer is required to reproduce the measured spectra. It is proposed that O is binding in a hollow site constituted by at least two Cu atoms and that up to 75% of the Pt atoms migrate below the surface.
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