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We have studied the interaction of water with stoichiometric CeO₂(111)/Cu(111), partially reduced CeO_2–x/Cu(111), and Pt/CeO₂/Cu(111) model catalysts by means of synchrotron–radiation photoelectron spectroscopy (SRPES), resonant photoemission spectroscopy (RPES) at the Ce 4d edge, infrared reflection absorption spectroscopy (IRAS), and density functional (DF) calculations. The principal species formed during adsorption of water at 160 K on CeO₂(111) films is chemisorbed molecular water. On the surface of CeO_2–x water partially dissociates yielding hydroxyl groups. By use of core-level PES, differentiation between chemisorbed water and hydroxyl groups is complicated by the overlap of the corresponding spectral features. Nevertheless, we determined three characteristic indicators for OH groups on ceria: (i) the presence of 1π and 3σ states in valence band (VB) PES; (ii) an increase of the binding …