Zusammenfassung
Single crystal adsorption calorimetry was applied to investigate the
heats of adsorption of CO and oxygen and the reaction heats for the
CO oxidation process on Pt111 at room temperature. Both sticking
probabilities and heats of adsorption for CO and oxygen are presented
as a function of coverage. These results an used to interpret the
subsequent measurements taken for the CO oxidation process on the
same surface. The initial heats of adsorption of CO and oxygen on
Pt111 are 180+/-8 and 339+/-32 kJ/mol, respectively. In addition
the pairwise lateral repulsive interaction between CO molecules in
a ((V)3x(r)oot 3)R30 degrees ordered layer at theta=1/3 is found
to be 4 kJ/mol. A detailed Monte Carlo modeling of the dissociative
adsorption and sticking probability of oxygen on Pt111 is performed.
The initial rapid fall in heat is attributed to adsorption oil defect
sites, and subsequent adsorption on the planar111 surface proceeds
with a third neighbor interaction energy between the oxygen adatoms
omega(3) similar to 22 kJ/mol. When gaseous CO reacts with preadsorbed
oxygen adatoms, the CO2 produced has an excess energy of 16+/-8 kJ/mol.
(C) 1997 American Institute of Physics.
Nutzer