The role of defects in the local reaction kinetics of CO oxidation on low-index Pd surfaces

D. Vogel, C. Spiel, M. Schmid, M. Stöger-Pollach, R. Schlögl, Y. Suchorski, G. Rupprechter

Institute of Materials Chemistry, Technische Universität Wien, 1060 Wien, Austria
Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
Institute of Applied Physics, and University Service Center for Transmission Electron Microscopy, Technische Universität Wien, 1040 Wien, Austria
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany

J. Phys. Chem. C 117 (2013) 12054-12060

The role of artificially created defects and steps in the local reaction kinetics of CO oxidation on the individual domains of a polycrystalline Pd foil was studied by photoemission electron microscopy (PEEM), mass spectroscopy (MS), and scanning tunneling microscopy (STM). The defects and steps were created by STM-controlled Ar+ sputtering and the novel PEEM-based approach allowed the simultaneous determination of local kinetic phase transitions on differently oriented µm-sized grains of a polycrystalline sample. The independent (single-crystal-like) reaction behavior of the individual Pd(hkl) domains in the 10-5 mbar pressure range changes upon Ar+ sputtering to a correlated reaction behavior, and the reaction fronts propagate unhindered across the grain boundaries. The defect-rich surface shows also a significantly higher CO tolerance as reflected by the shift of both the global (MS-measured) and the local (PEEM-measured) kinetic diagrams toward higher CO pressure.

Corresponding author: Y. Suchorski. Reprints also available from Michael Schmid (schmid at iap_tuwien_ac_at).

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