KINETICS OF H2O ADSORPTION ON CLEAN AND POTASSIUM PRECOVERED NI(111) SURFACES

The interaction of water with clean and potassium precovered Ni(111) was studied by X-ray photoelectron spectroscopy (XPS) in combination with an H2O particle beam for K submonolayer coverages. Equilibrium measurements of the kinetic parameters of the water desorption were performed in the H2O partial pressure range up to 2.10(-3) Pa. At temperatures between 155 K and 175 K the coverage dependent apparent Arrhenius parameters can be obtained. On the clean surface water adsorbs in a bilayer structure and no dissociation of the water molecules was observed, whereas for potassium covered surfaces a dissociation of approximately one water molecule perpotassium atom and a more complex adsorption behaviour was observed. The apparent Arrhenius parameters for the water desorption on the clean surface and for various potassium precoverages are presented. The different H2O layers are discussed and qualitatively compared with temperature programmed desorption (TPD) measurements.