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O: Fachverband Oberflächenphysik
O 24: Catalysis: Structural Effects
O 24.5: Talk
Tuesday, March 17, 2015, 11:30–11:45, MA 144
H2 activation on Pt-CeO2 mixed oxides for fuel cell applications — •Armin Neitzel1, Yaroslava Lykhach1, Tomas Skála2, Nataliya Tsud2, Mykhailo Vorokhta2, Kevin Charles Prince3, Vladimir Matolín2, and Jörg Libuda1 — 1FAU Erlangen-Nürnberg, Germany — 2Charles University in Prague, Czech Republic — 3Elettra-Sincrotrone Trieste, Italy
We investigated H2 activation on Pt-CeO2 mixed oxides as a function of Pt content by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. Pt-CeO2 mixed oxides were prepared by co-deposition of metallic Pt and Ce in oxygen atmosphere on well-ordered CeO2(111) buffer layers on Cu(111) at 110 K. Mixed oxides contain Pt2+, Pt4+, Ce4+ and fractions of Ce3+ ions. Pt2+ ions are stabilized at (100) nanofacets at the surface of nanostructured CeO2 films. Thermal stability of nanostructured Pt-CeO2 mixed oxides depends strongly on the Pt concentration. Annealing to 700 K in UHV leads to partial reduction of Pt2+ ions to metallic Pt particles once their number exceeds that of the (100) sites. H2 dissociation occurs only in presence of metallic Pt0 on the Pt-CeO2 substrates. Below 300 K, H2 activation yields hydroxyl groups which prevent hydrogen spillover from Pt to the substrate. Above 350 K, reduction of Pt2+ is accompanied by formation of oxygen vacancies due to the reaction of hydrogen with oxygen provided by the reverse oxygen spillover from the substrate to the Pt particles.