Presence of steps and edges has been proven to be important for catalytic reactions and in many cases these sites are the active sites transforming the reactants to products. The strong adsorption at the under coordinated step and edge sites leads to rather high coverages of the adsorbates. Hence the inclusion of adsorbate-adsorbate interactions can become important for catalytic activity descriptions. Here we propose a model to describe the interaction between the adsorbates adsorbed at two different sites of a same surface, since the metal nanoparticles in general consist of many different surface sites, such as terrace, steps, edges, kink and corners. For this study we have chosen the stepped (211) surface as our model surface. This surface consists of three different sites: steps, four-fold and terrace. The adsorbate-adsorbate interaction model is parameterized for the (211) surface to find the correct parameters to describe the interaction between different adsorbates on a single surface consisting multiple sites. Three model reactions are selected, namely steam reforming and dry reforming of methane and CO metanation, in order to verify the 'multi-site model'. The volcanoes shown in Figure 1 are obtained for CO methanation. The difference in the formulation between the previous one-site interaction model and this newly proposed multi-site interaction model, along with the difference in predicted catalytic activities are discussed in detail.Figure 1. CH4 formation rate in CO methanation as a function of the carbon (EC) and oxygen (EO) binding energiesas.

Adsorbate-adsorbate interaction model for the multisite microkinetic trend studies over stepped surfaces

248th National Meeting (2014)

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