Article,
The adsorption of CO, O2, and H2 on Pt: I. Thermal desorption spectroscopy studies
Surf. Sci., 69 (1): 85 - 113 (1977)
DOI: DOI: 10.1016/0039-6028(77)90163-7
Abstract
Thermal desorption spectroscopy (TDS) has been used to study the chemisorption
of CO, O2, and h2 on Pt. It has been found that TDS is quite sensitive
to local surface structure. Three single crystal and two polycrystalline
Pt surfaces were studied. One single crystal was cut to expose the
smooth, hexagonally close-packed plane of the fee Pt crystal (the
(111) surface). The other two single crystals were cut to expose
stepped surfaces consisting of smooth, hexagonally close-packed terraces
six atoms wide separated by one atom high steps (the 6(111) � (100)
and 6(111) � (111) surfaces). Only one predominant desorption state
was observed for CO and H adsorbed on the smooth (111) single crystal
surface, while two predominant desorption states were observed for
these gases adsorbed on the stepped single crystal surfaces. The
low temperature desorption states on the stepped surfaces are attributed
to desorption from the terraces, while the high temperature desorption
states are attributed to desorption from the steps. TDS of CO from
the polycrystalline foils exhibited some desorption states which
were similar to those observed on the stepped single crystal surfaces,
indicating the presence of adsorption sites on the polycrystalline
foils that were similar to the terrace and step sites on the stepped
single crystals. In general, these results suggest a high density
of defect sites on the polycrystalline foils which can not be attributed
simply to adsorption at grain boundaries. Oxygen was found to adsorb
well on the stepped single crystals and on the polycrystalline foils,
but not on the smooth (111) single crystal, under the conditions
of these experiments. This is attributed to a higher sticking probability
for dissociative O2 adsorption at steps or defects than on terraces.
