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Phase mixing and phase separation accompanying the catalytic oxidation of CO on Ir{100}

Lerotholi, T.J., Held, G. and King, D.A. (2007) Phase mixing and phase separation accompanying the catalytic oxidation of CO on Ir{100}. Surface Science, 601 (5). pp. 1285-1295. ISSN 0039-6028

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To link to this item DOI: 10.1016/j.susc.2006.12.067


The co-adsorption of CO and O on the unreconstructed (1 x 1) phase of Ir {100} was examined by low energy electron diffraction (LEED) and temperature programmed desorption (TPD). When CO is adsorbed at 188 K onto the Ir{100} surface precovered with 0.5 ML O, a mixed c(4 x 2)-(2O + CO) overlayer is formed. All CO is oxidised upon heating and desorbs as CO2 in three distinct stages at 230 K, 330 K and 430 K in a 2:1:2 ratio. The excess oxygen left on the surface after all CO has reacted forms an overlayer with a LEED pattern with p(2 x 10) periodicity. This overlayer consists of stripes with a local p(2 x 1)-O arrangement of oxygen atoms separated by stripes of uncovered It. When CO is adsorbed at 300 K onto the surface precovered with 0.5 ML O an apparent (2 x 2) LEED pattern is observed. LEED IV analysis reveals that this pattern is a superposition of diffraction patterns from islands of c(2 x 2)-CO and p(2 x 1)-O structures on the surface. Heating this co-adsorbed overlayer leads to the desorption of CO, in two stages at 330 K and 430 K; the excess CO (0.1 ML) desorbs at 590 K. LEED IV structural analysis of the mixed c(4 x 2) O and CO overlayer shows that both the CO molecules and the O atoms occupy bridge sites. The O atoms show significant lateral displacements of 0.14 angstrom away from the CO molecules; the C-O bond is slightly expanded with respect to the gas phase (1.19 angstrom); the modifications of the Ir substrate with respect to the bulk-terminated surface are very small. (c) 2006 Elsevier B.V. All rights reserved.

Item Type:Article
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11421
Uncontrolled Keywords:low energy electron diffraction (LEED), thermal desorption spectroscopy, chemisorption, catalysis, iridium, carbon monoxide, oxygen , LEED-IV DETERMINATION, CARBON-MONOXIDE, OXYGEN, SURFACE, COADSORPTION, ADSORPTION, GEOMETRY, RH(111), RH(100), KINETICS

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