Temperature effects on alkali-promoted CO dissociation on Ni(1 1 1)

Temperature effects on the alkali-induced CO dissociation on Ni(1 1 1) were studied by high-resolution electron energy loss spectroscopy. Measurements showed that CO adsorption on an alkali-precovered Ni(1 1 1) surface is partially dissociative in a temperature range up to 400 K and completely dissociative for higher sample temperatures. Depending on temperature an alkali critical precoverage for CO dissociation was found to exist, in agreement with theoretical calculations. Moreover, loss measurements demonstrated that Na and CO desorption are non-concurrent, in contrast with results obtained using thermal desorption spectroscopy for similar systems.