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Abstract

We report results of density functional theory calculations of the interaction of NO with the stoichiometric RuO2(110) surface that provide insights into the experimentally observed lack of reactivity for the system. We find that NO adsorbs on top of the undercoordinated Ru (Ru-cus) with an upright axis, and the adsorption energy (with zero-point contribution) changes from 1.61 eV for 0.5 ML to 1.49 eV for 1 ML coverage. Once all Ru-cus sites are occupied, NO adsorbs on O-bridge sites with adsorption energy of 0.66 eV, forming an asymmetric O…N–O surface complex. We also find a high dissociation barrier of 3.22 eV for NO on Ru-cus. Although the activation energy for oxidation of NO is calculated to be about 1.2 eV, the location of the final state makes the formation of NO2 only transient with a large probability of reverting back to NO. Additionally, the total energy difference for the reaction NO + NO → N2O + O on RuO2(110) is found to be about 1.35 eV. Comparison of results with those for a similar overlayer of CO on the surface show the NO–Ru-cus bond to be stronger than CO–Ru-cus, the difference arising from the contribution of the unpaired 2π* electrons for the former.