A new approach to the study of surface phenomena, measurements of diffusion rates, intermolecular distances and electronic properties of CO chemisorbed on supported platinum catalysts by nuclear magnetic resonance
Ansermet, Jean-Philippe
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https://hdl.handle.net/2142/25283
Description
Title
A new approach to the study of surface phenomena, measurements of diffusion rates, intermolecular distances and electronic properties of CO chemisorbed on supported platinum catalysts by nuclear magnetic resonance
Author(s)
Ansermet, Jean-Philippe
Issue Date
1985
Doctoral Committee Chair(s)
Slichter, C.P.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
surface phenomena
diffusion rates
intermolecular distances
electronic properties
CO chemisorbed
supported platinum catalysts
Nuclear magnetic resonance (NMR)
transverse relaxation
Language
en
Abstract
The author has applied magnetic resonance to study the chemisorption of CO on supported platinum particles. The particles are 10 to 50 Ansgtrom in diameter, supported on alumina. CO is 90% enriched with 13CO. NMR data were taken from 4 K to 600 K.
He shows that a measurement of transverse relaxation at 77 K can be used to measure relative distances among
molecules
in
the
adsorbed
layer.
His
measurements of
transverse
relaxation
and
of
spin-lattice
relaxation
are
consistent
with
the
geometry
of
CO
layers chemisorbed
on
single crystal
surfaces.
He has observed the narrowing of the NMR line and the effects of motion on transverse relaxation from 300 K to 600 K from which he deduces diffusion energies of 13 and 16 plus/minus 2 kcal/mol, in agreement with measurements of R. Lewis and R. Gomer of the diffusion of CO on Pt tips by Field Emission Microscopy.
He demonstrates that conduction electrons are present on CO and shows that the distribution of spin-lattice relaxation
times observed at 77 K reflects the various binding configurations present at the surface of each particle, irrespective of the particle size.
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