Ag(111) catalysts are important in the epoxidation of ethylene and other partial oxidation reactions. Computational models exploring the reactivity, kinetics, and surface reconstructions of these catalysts require insight into the distribution of reactants on the surface and within the subsurface of these catalysts. To explore the distribution of oxygen within the Ag catalyst, a lattice model is presented utilizing a cluster expansion parameterization of the oxygen adsorption energy based on Density Functional Theory (DFT) calculations. This methodology allows for relatively small DFT calculations to be used to include the single site Ag/O adsorption energy as well as the interaction between adsorbed oxygen atoms in much larger models of the Ag(111) surface and subsurface. The presented model includes 15 distinct high-symmetry sites on the surface and subsurface of Ag(111) including 4 surface sites, 3 subsurface sites over 3 subsurface layers, and 2 bulk sites.<br/><br/>The equilibrium distribution of adsorbed oxygen on the surface and subsurface of Ag(111) is calculated via Monte Carlo simulations using the developed Ag(111)/O model. Simulations explore the distribution of surface/subsurface oxygen as a function of total coverage. Additionally, grand canonical Monte Carlo simulations are performed to explore the oxygen coverage as a function of experimental conditions including molecular oxygen partial pressure and temperature. Low pressure (5x10<sup>-7</sup> Torr) conditions used in a previous experimental exploration of oxygen surface/subsurface population within Ag(111) as a function of deposition temperature are utilized to validate the developed model and provides additional insights into the experimental results. Higher pressure (0.75 Torr) conditions are performed to provide insight into the abundance of surface vs. subsurface oxygen during catalysis.

Determining the oxygen equilibrium distribution within Ag(111) catalysts under experimental conditions using Monte Carlo simulations and a cluster expansion Ag/O model

ACS Spring Meeting 2021

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