binding states of CO and H2 on clean and oxidized (111)Pt
Surf. Sci., 65 (1):
189 - 209 (1977)DOI: DOI: 10.1016/0039-6028(77)90301-6
Abstract
The binding states and sticking coefficients of CO and H2 on clean
and oxide covered (111)Pt are examined using flash desorption mass
spectrometry and Auger electron spectroscopy (AES). On the clean
surface at 78 K there is one major binding state of CO with a desorption
activation energy which decreases with coverage plus a second smaller
state, while H2 exhibits three binding states with peak temperatures
of 140, 230 and 310 K and saturation density ratios of 0.5 : 1 :
1. Desorption kinetics of CO are consistent with a first order state
with a normal pre-exponential factor of 1013 � 1 sec-1, while all
three peaks of H2 are broader than expected. Interpretations in terms
of anomalous pre-exponential factors, coverage dependent desorption
activation energies, and desorption orders are considered. On the
oxidized surface saturation densities of both gases are nearly identical
to those on the clean surface, but desorption temperatures are increased
significantly and the initial sticking coefficient on the oxide decreases
slightly for CO and increases slightly for H2.