Ethylene Epoxidation on Ag(100), Ag(110), and Ag(111) - A First-principles and Kinetic Monte Carlo Study

Ethylene epoxidation is commercially one of the most important selective oxidation reactions. Silver-based catalysts are the most common catalyst formulation in industry, albeit with significant doping. In this work, we present results from first-principles and kinetic Monte Carlo (kMC) modeling of the reaction on three pristine silver surfaces Ag(100), Ag(110), Ag(111), and on the missing-row reconstructed Ag(110). To better understand the kinetics on different surfaces and veraciously describe the surface coverages, we explicitly take into account the lateral interactions between the adsorbates and their effect on the activation barriers. Comparing with experimental data shows a good agreement with the modeling data especially for Ag(111) and somewhat worse for Ag(100). We show that Ag(100) offers better activity and activity than Ag(111). Differences in the active intermediates surface coverage were also studied. Furthermore, we studied the influence of alkali metals on selectivity. Our calculations show that the combination of electronegative Cl and electropositive Cs offers an optimal compromise between activity and selectivity.