Interaction of D2O with CeO2(001) investigated by temperature-programmed desorption and X-ray photoelectron spectroscopy

The interaction of D2O with the CeO2(001) surface was studied with temperat ure-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). It was found with TPD that D2O desorption occurs in three states with temp eratures of 152, 200, and 275 K, which are defined as multilayer D2O, weakl y bound surface D2O, and hydroxyl recombination, respectively. O Is XPS mea surements for high D2O exposures, where multilayer water desorption was obs erved in the TPD, resulted in emission from only the substrate and surface hydroxyls. This is likely due to a nonwetting behavior of D2O on this surfa ce with the formation of nanosized clusters. An analysis of the Ols XPS dat a indicates that the surface has a hydroxyl coverage of 0.9 monolayers for large water exposures at 85 K. This is consistent with a model in which the polar CeO2(001) surface can be stabilized by a reduction of the dipole in the top layer by the formation of a full monolayer of hydroxyls.