A HREELS, TPD study of NO adsorption, desorption, and reaction on clean and sulfur covered palladium (100)
The effect of sulfur poisoning on the adsorption, desorption and reaction of NO on the Pd(100) surface was studied using TPD, EELs, and LEED at sulfur precoverages ranging from zero to saturation (0.5 monolayer) for NO coverages varied between zero and saturation (0.65 ml). NO adsorption is primarily associative. A twenty-five percent decrease in the saturation coverage of NO was observed at a sulfur coverage of 0.1ml. Thereafter the NO coverage declined more slowly, but there was detectable NO adsorption at THETA/subS/ (sat). Three different loss peaks were detected by EELS. The losses occur at 1510, 1720, 1750 cm/sup -1/, assigned respectively to a bridge site, an atop site and a NO-S-Pd complex. The 1720 cm/sup -1/ loss frequency is coverage dependent. NO adsorption on the clean surface gives rise to a c(2x2) LEED pattern at 300K, and a p(4x2) at 410K, corresponding to coverages of 0.5 and 0.25ml, respectively. The p(4x2) pattern does not usually exhibit the p4mm symmetry of the surface. In the presence of 0.03 ml of sulfur the p(4x2) LEED pattern is not observed at any temperature, but the c(2x2) LEED pattern persists up to at least 0.2 ml sulfur. Only small amounts of N/sub 2/ and N/sub 2/O are observed to desorb during heating of adsorbed NO, and oxygen is not observed to desorb. At sulfur coverages above 0.10 ml only NO desorption is observed. The results may be accounted for using only steric interactions between CO and adsorbed sulfur.
- Research Organization:
- Dept. of Chemical Engineering, Stauffer III Building, Stanford Univ., Stanford, CA
- OSTI ID:
- 5332652
- Report Number(s):
- CONF-860425-
- Journal Information:
- Am. Chem. Soc., Div. Pet. Chem., Prepr.; (United States), Journal Name: Am. Chem. Soc., Div. Pet. Chem., Prepr.; (United States) Vol. 31:1; ISSN ACPCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ADSORPTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYTIC EFFECTS
CHALCOGENIDES
COHERENT SCATTERING
DESORPTION
DIFFRACTION
ELECTRON DIFFRACTION
ELEMENTS
METALS
NITROGEN
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
SATURATION
SCATTERING
SORPTION
SORPTIVE PROPERTIES
STEREOCHEMISTRY
SULFUR
SURFACE AREA
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS