Alkali monolayers on transition metal surfaces: electronic promotion in catalysis
Potassium monolayers on the platinum (111) crystal surface were studied most extensively. Ultraviolet photoelectron spectroscopy showed a large decrease in the work function of the surface when potassium was adsorbed. The heat of desorption of potassium decreased with increasing coverage. Low energy electron diffraction (LEED) showed that potassium forms hexagonal (close packed) overlayer structures. The effects of potassium on the chemisorption of various small molecules on Pt(111) were studied. Oxygen and nitric oxide were readily adsorbed and dissociated by potassium, forming stable potassium-oxide complexes on the surface. Adsorption heat of carbon monoxide on Pt(111) increased with potassium coadsorption. High resolution electron energy loss spectroscopy showed that the carbon-oxygen bond of adsorbed carbon monoxide was weakened by potassium. Adsorption heat of benzene, however, was decreased by coadsorbed potassium. A molecular orbital explanation was given to explain the effects of potassium. CO hydrogenation reactions performed on metal foils showed that the addition of alkali adlayers tends to decrease the overall rate of reaction. Changes in selectivity were noted, shifting the product distribution in favor of higher molecular weight species and from alkanes to alkenes.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5609614
- Report Number(s):
- LBL-16594; ON: DE84002570
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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10 SYNTHETIC FUELS
ALKALI METALS
CATALYTIC EFFECTS
BENZENE
ADSORPTION
CARBON MONOXIDE
HYDROGENATION
METHANATION
CATALYSIS
NITRIC OXIDE
OXYGEN
PLATINUM
SORPTIVE PROPERTIES
POTASSIUM
ADSORPTION HEAT
CHEMISORPTION
DESORPTION
WORK FUNCTIONS
AROMATICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
ENTHALPY
FUNCTIONS
HYDROCARBONS
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
360104* - Metals & Alloys- Physical Properties
090121 - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989)