| Abstract
| - Periodic density functional calculations are reported for NO dissociation on the Rh(221) and RhCu(221)surfaces. The analysis of the reaction pathways indicates that the presence of steps results not only in newadsorption sites for NO adsorption but also on the appearance of a completely new reaction pathway withactivation energies which are smaller than those found previously for the regular Rh(111) surfaces. At lowNO surface coverage and a small Cu density, the presence of Cu on Rh(221) does not change the reactivityof rhodium stepped surfaces toward NO dissociation, since the effective activation energy barrier is higher(1.32 eV for RhCu(221) versus 1.17 eV for Rh(221)). The essential reason is the increased metastability ofthe step sites. However, for stronger NO coverage or a higher Cu density, the stepped RhCu(221) surface isexpected to exhibit an enhanced activity: either by increasing the occupancy of these metastable sites alongthe RhCu steps or by removing the possibility of highly stable pure Rh bridge step sites.
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