High Chemical Activity of a Perovskite Surface: Reaction of CO with Sr3Ru2O7

B. Stöger, M. Hieckel, F. Mittendorfer, Z. Wang, D. Fobes, J. Peng, Z. Mao, M. Schmid, J. Redinger, U. Diebold

Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
Faculty of Physics and Center for Computational Materials Science, University of Vienna, 1090 Wien, Austria
Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.

Phys. Rev. Lett. 113 (2014) 116101

Adsorption of CO at the Sr3Ru2O7 surface was studied with low-temperature scanning tunneling microscopy and density functional theory. In situ cleaved single crystals terminate in an almost perfect SrO surface. At 78 K, CO first populates impurities and then adsorbs above the apical surface O with a binding energy Eads = -0.7 eV. Above 100 K, this physisorbed CO replaces the surface O, forming a bent CO2 with the C end bound to the Ru underneath. The resulting metal carboxylate (Ru-COO) can be desorbed by STM manipulation. A low activation (0.2 eV) and high binding (-2.2 eV) energy confirm a strong reaction between CO and regular surface sites of Sr3Ru2O7; likely, this reaction causes the "UHV aging effect" reported for this and other perovskite oxides.

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Reprints also available from Ulrike Diebold (diebold at iap_tuwien_ac_at).