Abstract
We have observed the displacement of adsorbed CO from the Ni(111) surface by ambient hydrogen present in the pressure range 10{sup -9} to 10 torr. In situ work function measurements have been used to measure the rates of CO desorption during heating in hydrogen. The desorption temperature shifts monotonically from 420 K under ultrahigh vacuum (UHV) conditions to 320 K in the presence of >1 Torr H{sub 2}. This implies a net decreases of the CO desorption energy from 30 kcal/mol in UHV to 22 kcal/mol in the presence of hydrogen. The influence of hydrogen on the CO desorption kinetics may be directly related to a shift in CO binding site induced by the presence of ambient hydrogen. This hydrogen-induced shift of CO molecules from linear sites to bridging sites on the Ni(111) surface has been observed quite recently using FTIR measurements. 21 refs., 8 figs.
Published Version
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