Journal
SURFACE SCIENCE
Volume 621, Issue -, Pages 31-39Publisher
ELSEVIER
DOI: 10.1016/j.susc.2013.10.018
Keywords
Surface oxide reduction; Pd75Ag25(100); Pd(100); Photoelectron spectroscopy; Avrami kinetics; Density functional theory
Categories
Funding
- Research Council of Norway [138368/V30]
- Strategic Area Materials at the Norwegian University of Science and Technology, NordForsk
- Swedish Research Council
- Crafoord Foundation
- Knut and Alice Wallenberg Foundation
- Foundation for Strategic Research (SSF)
- Anna and Edwin Berger Foundation
- European Community-Research Infrastructure Action through the Integrated Infrastructure Initiative Integrating Activity on Synchrotron and Free Electron Laser Science
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The reduction of the (A root 5x root 5)R27 degrees surface oxide on Pd(100) and Pd75Ag25(100) surfaces by CO has been investigated by high-resolution X-ray photoelectron spectroscopy in combination with kinetic analysis using the Avrami-Erofeev theory. For both surfaces we observed faster reduction with increasing temperature. Kinetic analysis indicates that the reduction process is phase boundary controlled for Pd(100) in the temperature range investigated, from 30 degrees C to 120 degrees C On Pd75Ag25(100) the surface oxide reduction is significantly slower compared to Pd(100). Also in this case, a phase boundary controlled reduction of the surface oxide is observed at temperatures of 120 C and above, while at T <= 70 degrees C the reduction is found to be diffusion limited. Density functional theory calculations show that the presence of silver in the outermost surface layer significantly increases the CO diffusion barriers on the reduced areas, supporting a diffusion limited reduction process for Pd75Ag25(100) at lower temperatures. (C) 2013 Elsevier B.V. All rights reserved.
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