CO adsorption on Ni(1 0 0): Evidences for a weakly bound phase by HREELS measurements

• Published in: Surface science Vol. 600; no. 7; pp. 1456 - 1461
• Main Authors: Formoso, V., Marino, A., Chiarello, G., Agostino, R.G., Caruso, T., Colavita, E.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-04-2006; Amsterdam Elsevier Science; New York, NY
• Subjects: Catalysis; Chemisorption; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; HREELS; Physics; Solid–gas interface; Solid–gas interface; Chemisorption; HREELS; Catalysis; EEL spectroscopy; Solid-gas interface; Coadsorption; Gas solid interface; Nickel
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2006.01.052

The vibrational properties of CO on Ni(1
0
0) were investigated by high resolution electron energy loss spectroscopy. Loss measurements were performed as a function of temperature and CO exposures. At room temperature, regardless of CO coverage, we found stretching energies at 250
meV and 240
meV, assigned to CO at atop and bridge sites, respectively. At low temperature and for CO exposures lower than 0.6
L, the loss spectra showed a single stretching peak at 240
meV which is assigned to CO at bridge sites. For higher doses, a new intense peak at 260
meV appeared in the loss spectra. The rise of this new loss strongly influenced the intensity of the peak at 240
meV suggesting the occurrence of dipole couplings between adjacent CO molecules. This unusual high stretching frequency leads us to assign the peak at 260
meV to the stretching vibration of CO molecules which are weakly bonded to the Ni surface. We suggest that the formation of this phase is due to an electronic effect arising from a reduced back donation of electrons into the empty π orbital of CO.