Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 28: Heterogeneous catalysis II
O 28.10: Talk
Tuesday, March 27, 2012, 12:45–13:00, MA 042
Concentration dependent oxidation of Pd-Rh alloy nanoparticles on MgAl2O4(001) — •Patrick Müller1, Uta Hejral1, Uta Rütt2, and Andreas Stierle1 — 1University of Siegen, Walter-Flex-Str. 3, 57068 Siegen, Germany — 2Deutsches Elektronen-Synchroton (DESY), Notkestraße 85, 22607 Hamburg, Germany
Noble metal alloy nanoparticles play an eminent role in heterogeneous catalysis, especially as catalyst in automotive exhaust control (CO oxidation, NOx reduction). Understanding oxidation and reduction behavior of Pd-Rh alloy nanoparticles on the nanoscale is of great importance for improving their functionality [1]. To this end we prepared a combinatorial sample containing five stripes of epitaxial alloy nanoparticles of varying Pd-Rh concentrations on an MgAl2O4(001) support.
We present concentration-dependent size and shape changes of epitaxial Pd-Rh alloy nanoparticles as well as bulk oxide formation observed in-situ during oxidation. The experiments were carried out in a high pressure compatible UHV chamber at the high energy materials science beamline P07 at DESY in the temperature range between 570 K and 670 K and at oxygen pressures from UHV up to 0.1mbar. We employed grazing incidence x-ray reciprocal space mapping using a 2D detector and complementary x-ray reflectivity at an energy of 85 keV [2]. Our results demonstrate a strong influence of the nanoparticles composition on the oxidation behavior.
[1] F. Tao, et al., Science Vol. 322, 1164170 (2008)
[2] P. Nolte, et al., Phys. Rev. B 77, 115444 (2008)