Abstract
LEED. TPRS. and RAIRS experiments combined with DFT calculations have been used to study CO oxidation on Rh(100) from preadsorbed O and CO and to unravel how the reaction kinetics is influenced by the configuration of the adsorbed reactants. At least four different regimes are identified in increasing order of reactivity: near zero coverage, isolated CO and O species react with the highest activation energy observed in this work (105 ± 4 kJ/mol). In the second regime. oxygen is present in a p(2 x 2) structure and reacts with bridge bonded CO, with an activation energy of 77 ± 8 kJ/mol. In the third regime. the reactivity is associated with on-top CO in defects of a c(2 x 2) oxygen layer. at an estimated activation energy of 58 ± 10 kJ/mol. In the last and most reactive regime. the oxygen adlayer has (2 x 2)-pg order with the top metal layer reconstructed. According to DFT calculations. CO adsorption lifts the reconstruction. Oxygen occupies 4-fold hollow and bridge sites: the latter react with bridged CO. The general trend is that if the reactants become destabilized by repulsive lateral interactions. the rate of reaction to CO 2 increases.
Published Version
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