Comparative study of the coadsorption of CO and NO on Pd(100), Pd(111), and silica-supported palladium particles with infrared reflection-absorption spectroscopy
- Texas A M Univ., College Station, TX (United States)
The coadsorption of nitric oxide and carbon monoxide on Pd(100), Pd(111), and a model silica-supported palladium catalyst has been investigated with infrared reflection-absorption spectroscopy (IRAS) in the temperature range 100-500 K. The palladium surfaces were in equilibrium with a 1 x 10[sup [minus]6] Torr equimolar mixture of CO and NO during the FT-IRAS studies. The structure and coverage of the adsorbed layers strongly depend on the surface temperature and crystal orientation. On all surfaces, CO and NO form molecularly mixed overlayers, and the CO/NO coverage ratio increases with a decrease in surface temperature. On Pd-(100), both CO and NO adsorb at the 2-fold bridging sites at all temperatures. The coverage for CO and NO is similar at temperatures above 400 K, whereas at 100 K the CO/NO ratio is approximately 5. On Pd(111), the majority surface species is NO, which adsorbs at the 3-fold hollow sites at >400 K. At lower temperatures, CO adsorbs at the bridging sites and the NO at the hollow sites converts to atop NO. At <200 K the overlayer consists of approximately 0.25 monolayer of NO on the atop sites and approximately 0.5 monolayer of CO on the nearby bridging sites. 40 refs., 5 figs.
- OSTI ID:
- 6768530
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:37; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ADSORPTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
ELECTRON DIFFRACTION
ELEMENTS
INFRARED SPECTRA
METALS
MINERALS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
SCATTERING
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENTS
ULTRAHIGH VACUUM