Water interaction with CeO2(1 1 1)/Cu(1 1 1) model catalyst surface

Interaction of water with fully oxidized and partially reduced CeO2(1 1 1) thin film model catalyst grown on a Cu(1 1 1) surface was investigated by photoelectron spectroscopy (PES), scanning tunneling microscopy (STM) and temperature programmed desorption (TPD). On the stoichiometric surface water adsorbs molecularly at low temperatures (≤120 K) while on the reduced surface the adsorption is partially dissociative with formation of OH groups. STM indicates no morphology variation and a very sensitive Ce 4d–4f resonant photoelectron spectroscopy (RPES) no noticeable change of the oxidation state of ceria upon water adsorption and subsequent complete desorption. Formation of co-adsorbed phase of residual water with OH during molecular water desorption, on the other hand, leads to a substantial resonance of the Ce3+ photoemission state around 170 K. We propose that this behaviour indicating ceria reduction is in this case an electronic effect of the Ce 4f charge accumulation and Ce 5d charge depletion.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (333 K)Download as PowerPoint slideHighlights► Water adsorption on cerium oxide model catalyst. ► Water dissociation on oxygen vacancies. ► H2O and OH induce at 170 K ceria reduction and Ce3+ photoelectron resonance. ► STM of CeO2(1 1 1) surface. ► CeO2(1 1 1) growth on Cu(1 1 1) single crystal. ► Molecular water adsorption and desorption.