Skip to main content
Other
In situ XPS study of Pd(111) oxidation. Part 1: 2D oxide formation in 10 3 mbar O2
Birck and NCN Publications
  • Dmitry Zemlyanov, Materials and Surface Science Institute and Physics Department, University of Limerick; Birck Nanotechnology Center, Purdue University
  • Balazs Aszalos-Kiss, Materials and Surface Science Institute and Physics Department, University of Limerick
  • Evgueni Kleimenov, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Detre Teschner, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Spiros Zafeiratos, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Michael Havecker, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Axel Knop-Gericke, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Robert Schlogl, Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft
  • Harald Gabasch, Institut fu¨ r Physikalische Chemie, Universita¨ t Innsbruck
  • Werner Unterberger, Institut fu¨ r Physikalische Chemie, Universita¨ t Innsbruck
  • Konrad Hayek, Institut fur Physikalische Chemie, Universitat Innsbruck
  • Bernhard Klotzer, Institut fur Physikalische Chemie, Universitat Innsbruck
Abstract

The oxidation of the Pd(111) surface was studied by in situ XPS during heating and cooling in 3 · 10 3 mbar O2. A number of adsorbed/dissolved oxygen species were identified by in situ XPS, such as the two dimensional surface oxide (Pd5O4), the supersaturated Oads layer, dissolved oxygen and the ð ffiffiffiffiffi p67 ffiffiffiffiffi p67ÞR12.2 surface structure. Exposure of the Pd(111) single crystal to 3 · 10 3 mbar O2 at 425 K led to formation of the 2D oxide phase, which was in equilibrium with a supersaturated Oads layer. The supersaturated Oads layer was characterized by the O 1s core level peak at 530.37 eV. The 2D oxide, Pd5O4, was characterized by two O 1s components at 528.92 eV and 529.52 eV and by two oxygen-induced Pd 3d5/2 components at 335.5 eV and 336.24 eV. During heating in 3 · 10 3 mbar O2 the supersaturated Oads layer disappeared whereas the fraction of the surface covered with the 2D oxide grew. The surface was completely covered with the 2D oxide between 600 K and 655 K. Depth profiling by photon energy variation confirmed the surface nature of the 2D oxide. The 2D oxide decomposed completely above 717 K. Diffusion of oxygen in the palladium bulk occurred at these temperatures. A substantial oxygen signal assigned to the dissolved species was detected even at 923 K. The dissolved oxygen was characterised by the O 1s core level peak at 528.98 eV. The ‘‘bulk’’ nature of the dissolved oxygen species was verified by depth profiling. During cooling in 3 · 10 3 mbar O2, the oxidised Pd2+ species appeared at 788 K whereas the 2D oxide decomposed at 717 K during heating. The surface oxidised states exhibited an inverse hysteresis. The oxidised palladium state observed during cooling was assigned to a new oxide phase, probably the ð ffiffiffiffiffi p67 ffiffiffiffiffi p67ÞR12.2 structure.

Keywords
  • X-ray photoelectron spectroscopy,
  • Chemisorption,
  • Oxidation,
  • Surface chemical reaction,
  • Palladium,
  • Single crystal surfaces,
  • Low index single crystal surfaces,
  • oxygen
Date of this Version
1-13-2006
Citation
doi:10.1016/j.susc.2005.12.020
Citation Information
Dmitry Zemlyanov, Balazs Aszalos-Kiss, Evgueni Kleimenov, Detre Teschner, et al.. "In situ XPS study of Pd(111) oxidation. Part 1: 2D oxide formation in 10 3 mbar O2" (2006)
Available at: http://works.bepress.com/dmitry_zemlyanov/9/