Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Heterogeneous catalysis I

O 15.8: Vortrag

Montag, 26. März 2012, 17:45–18:00, MA 042

Interaction of H₂O with ceria and Pt/ceria model catalysts — •Y. Lykhach¹, G. N. Vayssilov², M. Happel¹, N. Tsud³, H. A. Aleksandrov², T. Skála⁴, V. Johánek³, P. St. Petkov², K. C. Prince⁴, V Matolín³, K. M. Neyman^5,6, and J. Libuda¹ — ¹FAU Erlangen-Nürnberg, Germany — ²University of Sofia, Bulgaria — ³Charles University in Prague, Czech Republic — ⁴Sincrotron Trieste, Italy — ⁵Universitat de Barcelona, Spain — ⁶ICREA, Barcelona, Spain

The interaction of H₂O with ceria-based catalysts plays an important role in hydrogen production via reforming. Still, we are lacking detailed understanding of the water surface chemistry on pure and metal-loaded ceria. We have performed a comprehensive investigation of water adsorption and dissociation on stoichiometric CeO₂(111), partially reduced CeO₂−x, and Pt/CeO₂(111) films on Cu(111), combining high resolution photoelectron spectroscopy (HR-PES), resonant PES, infrared absorption spectroscopy (IRAS), and density functional theory (DFT). Identification of OH-derived spectral signatures and chemisorbed water on ceria turned out to be difficult, both in HR-PES or IRAS. Despite strong signals from OH/H₂O in O 1s core level spectra upon annealing to 500 K, no corresponding vibrational bands were detected on both CeO₂ and CeO₂−x films above 200 K. DFT suggest that these experimental findings result from strong hydrogen bond between OH and neighboring oxygen anions and strong bending of OH group. Dissociation and spillover on Pt/CeO₂(111) is monitored by RPES via the Ce oxidation state as a function of temperature.