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The adsorption and dissociation of carbon monoxide has been studied with plane wave density functional theory on Rh(111), the stepped Rh(553) surface and on Ni decorated Rh(553). The most favorable adsorption site has been identified by a systematic calculation of the adsorption energies and the stretching frequency of CO adsorbed on these sites. The clean, stepped (553) surface binds molecular CO more strongly than the flat (111) surface on low-coordinated sites, but on the Ni-decorated surface the binding is stronger on high-coordinated sites. The barrier for dissociation, referred to gas-phase zero, on the stepped Rh(553) and Ni decorated Rh(553) surface is ~ 1 eV lower than on the flat Rh(111). Since the molecular adsorption energies of CO on clean Rh(553) and Ni decorated Rh(553) are similar, the difference of ~ 1 eV between the dissociation barriers means that the reaction rate of this process is substantially different compared to the flat Rh(111) surface. We also explored the possibility of tuning the reactivity of the step sites by exchanging the step decoration with other 4d (Ru, Rh, Pd, Ag) and 5d (Os, Ir, Pt) metals. Our results suggest that with increasing band filling of the step-decorating metal atom, the dissociation at the steps becomes less exothermic with the transition state being shifted increasingly towards the final state. |