O2 dissociation is a key step in many surface catalytic reactions involving oxidation. O2 dissociation over Pt(111) surface is known to be affected by the oxygen adatom (O*) coverage at the surface. The O* coverage not only influences the energetics of further O2 dissociative adsorption (i.e., molecular chemisorption energy, dissociation barrier and O* binding energy), but also determines the reaction site statistics (i.e., how many types of dissociation sites and their site densities). The total rate of O2 dissociation is modeled through a sum over the rates of all types of dissociation sites weighted by their corresponding site densities.
Here we take advantage of a Cluster-Expansion (embedded in a Grand Canonical Monte Carlo method) of O* on Face Centered Cubic sites of Pt(111) surface to efficiently predict O* configurations as a function of temperature and coverage. With the predicted configurations, we identify types of dissociation sites according to CE O* binding energy and retrieve site densities. We then use Density Functional Theory to study O2 dissociation rates at each type of site. Eventually, we can construct a model to predict reaction properties incorporating coverage effects, such as reaction order and apparent activation energy under various reaction conditions.