Infrared reflection absorption spectral study for CO adsorption on Pd/Pt(1 1 1) bimetallic surfaces

N. Todoroki, H. Osano, T. Maeyama, H. Yoshida, T. Wadayama

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Infrared reflection absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on 0.15 nm-thick-0.6 nm-thick Pd-deposited Pt(1 1 1) bimetallic surfaces: Pd x /Pt(1 1 1) (where x is the Pd thickness in nanometers) fabricated using molecular beam epitaxial method at substrate temperatures of 343 K, 473 K, and 673 K. Reflection high-energy electron diffraction (RHEED) measurements for Pd 0.15-0.6 nm /Pt(1 1 1) surfaces fabricated at 343 K showed that Pd grows epitaxially on a clean Pt(1 1 1), having an almost identical lattice constant of Pt(1 1 1). The 1.0 L CO exposure to the clean Pt(1 1 1) at room temperature yielded linearly bonded and bridge-bonded CO-Pt bands at 2093 and 1855 cm -1 . The CO-Pt band intensities for the CO-exposed Pd x /Pt(1 1 1) surfaces decreased with increasing Pd thickness. For Pd 0.3 nm /Pt(1 1 1) deposited at 343 K, the 1933 cm -1 band caused by bridge-bonded CO-Pd enhanced the spectral intensity. The linear-bonded CO-Pt band (2090 cm -1 ) almost disappeared and the bridge-bonded CO-Pd band dominated the spectra for Pd 0.6 nm /Pt(1 1 1). With increasing substrate temperature during the Pd depositions, the relative band intensities of the CO-Pt/CO-Pd increased. For the Pd 0.3 nm /Pt(1 1 1) deposited at 673 K, the linear-bonded CO-Pt and bridge-bonded CO-Pd bands are located respectively at 2071 and 1928 cm -1 . The temperature-programmed desorption (TPD) spectrum for the 673 K-deposited Pd 0.3 nm /Pt(1 1 1) showed that a desorption signal for the adsorbed CO on the Pt sites decreased in intensity and shifted ca. 20 K to a lower temperature than those for the clean Pt(1 1 1). We discuss the CO adsorption behavior on well-defined Pd-deposited Pt(1 1 1) bimetallic surfaces.

Original languageEnglish
Pages (from-to)943-947
Number of pages5
JournalApplied Surface Science
Issue number4
Publication statusPublished - 2009 Nov 30


  • Carbon monoxide
  • Infrared reflection absorption spectroscopy
  • Palladium
  • Pt(1 1 1)
  • Reflection high-energy electron diffraction
  • Thermal desorption spectroscopy


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