Chemical modification of surfaces: the effect of potassium on the chemisorption of molecules on transition metal crystal surfaces

Thesis/Dissertation · Sun Jan 01 00:00:00 EST 1984

OSTI ID:5576852

Crowell, J E

The role of alkali metals in modifying the chemistry at metal surfaces has been explored under ultrahigh vacuum (UHV) conditions. The structure and bonding of pure alkali monolayers and that of coadsorbed molecules has been determined using a variety of surface sensitive spectroscopies. Surface vibrational spectroscopy using high resolution electron energy losses has been utilized and has revealed the nature of the interaction of alkalis with molecular adsorbates. The implications of the chemisorption changes induced by alkalis and their role in industrial catalytic reactions is discussed. The physical and chemical properties of pure potassium monolayers and its effect on the adsorption of oxygen, carbon monoxide and benzene on the (111) faces of platinum and rhodium single crystals are described. Potassium adsorption on both surfaces is quite similar. Potassium forms hexagonally close packed structures that are incommensurate with the substrate. The heat of desorption of potassium on these surfaces decreases with increasing potassium coverage. The surface free electron density increases and the work function decreases substantially with alkali adsorption, indicating charge transfer occurs from potassium to the substrate. The major influence of potassium is to increase the surface electron density, which, for molecular adsorbates with low lying vacant orbitals of the correct symmetry, can lead to substantial changes in their bonding with the surface.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 5576852
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BENZENE
CHEMISORPTION
STRUCTURAL CHEMICAL ANALYSIS
CARBON MONOXIDE
OXYGEN
PLATINUM
SURFACE PROPERTIES
SURFACE TREATMENTS
POTASSIUM
ADSORPTION
CATALYTIC EFFECTS
CHEMICAL PROPERTIES
PHYSICAL PROPERTIES
RHODIUM
ADSORPTION HEAT
CHARGE DENSITY
CHEMICAL BONDS
CRYSTAL FACES
DESORPTION
ENERGY-LOSS SPECTROSCOPY
EXPERIMENTAL DATA
HEXAGONAL LATTICES
ULTRAHIGH VACUUM
ALKALI METALS
AROMATICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DATA
ELECTRON SPECTROSCOPY
ELEMENTS
ENTHALPY
HYDROCARBONS
INFORMATION
METALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
360104* - Metals & Alloys- Physical Properties
360103 - Metals & Alloys- Mechanical Properties
400201 - Chemical & Physicochemical Properties