Reaction and chemisorption of small molecules on clean and chemically modified transition metal surfaces

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5922464

Greenlief, C M

TiO/sub 2/ overlayers on polycrystalline Pt have been characterized by x-ray photoelectron spectroscopy. Vacuum annealing of these thin films had two significant effects: (1) Most of the Ti/sup 4 +/ was reduced to Ti/sup 3 +/ and (2) An equilibrium coverage of the reduced species was reach for initial coverages of TiO/sub 2/ greater than about 0.9 ML. Depth profiles indicate that the reduced titania species diffuses into Pt. The isotope exchange of H/sub 2/ and D/sub 2/ has been studied on Pt(111) by temperature programmed desorption (TPD). Below 120 K there is no exchange between H/sub 2/ (g) and D(a) on a fully saturated surface. Above 120 K, isotope exchange occurs readily. When the substrate is dosed at temperatures below 250 K the desorption of D/sub 2/ is complete at temperatures significantly below those for H/sub 2/ and HD irrespective of the order of adsorption. This isotope effect is attributed to the preferential accommodation of H into the near surface region of Pt. There is no isotope effect in desorption after dosing above 250K. This is interpreted in terms of surface-subsurface exchange during dosing. The chemisorption properties of carbon monoxide on potassium-predosed Pt(111) have been studied by TPD and static secondary ion mass spectrometry (SSIMS). The formation and decomposition kinetics of ethylidyne on Ru(0001) have been studied using SSIMS and TPD. The C(KVV) x-ray excited Auger spectra have been obtained and deconvoluted for condensed multilayers and adsorbed monolayers of acetylene, ethylene, and ethane on Ni(100) at 20 K. Combining both photoemission and Auger results, the hole-hole repulsion energy in the Auger final state are determined for each molecule.

• Research Organization: Texas Univ., Austin (USA)
• OSTI ID: 5922464
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ACETYLENE
ADSORPTION
ALKANES
ALKENES
ALKYNES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
DEUTERIUM
ELEMENTS
ETHANE
ETHYLENE
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
METALS
NICKEL
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
SORPTION
SORPTIVE PROPERTIES
STABLE ISOTOPES
SURFACE PROPERTIES
TEMPERATURE EFFECTS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS