Thickness-Dependent Reactivity of O2on Cu Layers Grown on Ru(0001) Surfaces

The reaction of diatomic molecules on bimetallic surfaces, formed by one to few monolayers of a metal adsorbed on a different metal substrate, is relevant to understand the role of surface strain and substrate chemical binding in catalysis, which is interesting for industrial applications, challenges existing state-of-the-art theoretical methods, due to the additional complexity associated with having a molecule with triplet spin multiplicity. Here, we have studied the interaction of O2with CuxML/Ru(0001) (xbeing the number of Cu monolayers), for which experimental data are available, by means of multidimensional classical dynamics simulations based on first-principles potential energy surfaces. Our results show, on the one hand, that the inclusion of the surface temperature on the simulations is essential to reproduce the experimental observations, and therefore, to analyze the physical mechanisms behind these observations, and, on the other hand, that electronic effects due to the binding between the two metallic species are only relevant for one Cu monolayer, whereas strain is responsible for the observed reactivity in O2interacting with Cu(x≥2)ML/Ru(0001).