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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Epitaxy, growth and adsorbates
O 56.16: Talk
Thursday, March 26, 2009, 18:45–19:00, SCH A316
Dissociative adsorption of methane on surface oxide structures of PdPt alloys — •Arezoo Dianat1, Nicola Seriani2, Manfred Bobeth1, Wolfgang Pompe1, and Lucio Colombi Ciacchi3 — 1Institute for Materials Science, Dresden University of Technology, Germany — 2Fakultät für Physik, Universität Wien, Austria — 3Faculty of Production Engineering, University of Bremen, Germany
Oxides of Pd and Pt are known for their high activity in the catalytic combustion of methane. It was reported that bimetallic Pd-Pt oxide systems exhibit higher activity for CH4 combustion than PdO. To get some insight into the catalytic activity of PdPt we have studied the dissociative adsorption of CH4 on oxidised PdPt surfaces using DFT. First, the stability of various surface oxides was investigated, including oxygen adsorbed on the surface, subsurface oxygen, and thin oxide films. As base structures for the thin oxide films we have chosen PdO(101)/Pd(100), α-PtO2/Pt(111) and Pt3O4/Pt(100), which show small lattice misfit between film and substrate. Adsorption energies for oxygen on the PdPt surface and in subsurface positions are higher than on the monometals. For thin oxide films, doping of Pd or Pt results in lower mean oxygen binding energies compared to pure Pd and Pt oxide films. The decomposition of CH4 to CH3 and H has been found to be endothermic on metal surfaces, but it becomes exothermic on oxidised surfaces. Among the considered monometallic oxide structures, Pt3O4/Pt(100) shows the highest CH4 adsorption energy. For some of the bimetallic oxide configurations considered, the CH4 adsorption energy was found to be higher than on the monometallic oxides.