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Transient stuctures of PdO during CO oxidation over Pd(100)

Mikhail Shipilin ; Johan Gustafson ; Chu Zhang ; Lindsay Merte ; Andreas Stierle ; Uta Hejral ; Uta Ruett ; Olof Gutowski ; Magnus Skoglundh (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Per-Anders Carlsson (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Edvin Lundgren
Journal of Physical Chemistry C (1932-7447). (2015)
[Artikel, refereegranskad vetenskaplig]

In situ high-energy surface X-ray diffraction was employed to determine the surface structure dynamics of a Pd(100) single crystal surface acting as a model catalyst to promote CO oxidation. The measurements were performed under semi-realistic conditions, i.e. 100 mbar total gas pressure and 600 K sample temperature. The surface structure was studied in detail both in a steady gas ow and in a gradually changing gas composition with a time resolution of 0.5 sec. Our results show that \sqroot-PdO(101) surface oxide forms in a close to stoichiometric O2 and CO gas mixture as the mass-spectrometry indicates a transition to a highly active state with the reaction rate limited by the CO mass transfer to the Pd(100) surface. Using a low excess of O2 in the gas stoichiometry, islands of bulk oxide grow epitaxially in the same (101) crystallographic orientation of the bulk PdO unit cell according to a Stranski-Krastanov type of growth. The morphology of the islands is analyzed quantitatively. Upon further increase of the O2 partial pressure a polycrystalline Pd oxide forms on the surface.

Nyckelord: HESXRD, SXRD, Pd, PdO, islands, CO oxidation, heterogeneous catalysis



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Denna post skapades 2015-06-15. Senast ändrad 2015-11-09.
CPL Pubid: 218377

 

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