Hydrogen vibrational density of states of adsorbed water on rare-earth modified zirconia

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Rare-earth (RE) doped ZrO 2 prepared by a method of coprecipitation from aqueous solution shows many properties, such as good thermal stability and large surface area ( ∼ 80m 2/g), that are suitable for use as catalyst supports and sorbents for a variety of molecules. We have measured the vibrational densities of states of surface hydroxyl groups as well as physisorbed water molecules in La 0.1Zr 0.9O 1.95 and Nd 0.1Zr 0.9O 1.95 by inelastic neutron scattering. The spectrum of dry RE-ZrO 2 exhibits a peak at about 455 meV characteristic of the O H stretch vibrations of surface hydroxyl groups. At submonolayer coverage of H 2O this peak broadens and shifts to a slightly lower energy. At higher coverage three bands, corresponding to the O H stretch (∼ 430 meV), H O H bend (∼ 200 meV) and librational motion ( ∼ 80 meV), were observed. The decreasing energy and larger width of the O H stretch band with increasing H 2O coverage indicate the influence of hydrogen bonding on the motion of water molecules.