(685a) N2 Activation and Spillover on Single-Atom Alloy Catalysts: A Theoretical Study

Ammonia (NH₃) is one of the most important feedstocks for the production of chemicals and fertilizer making it vital to the global economy at large. Activation of molecular nitrogen (N₂) is seen as a critical step in the Haber-Bosch process, which is the ubiquitous industrial process for the production of ammonia. It has been shown that the activity of monometallic catalysts commonly used for ammonia synthesis is restricted by the scaling relation that low activation energy of N₂ correlates with strong adsorption of intermediates, which blocks adsorption sites and hinders NH₃ synthesis. Heterogeneous catalysts that allow facile activation of N₂ and weak binding of N atoms would exhibit the optimal efficiency for these reactions. In this study, we employ first principles calculations and microkinetic modeling to study N₂ activation and spillover on alloy surfaces. We demonstrate that incorporating single-atom alloy sites allows breaking scaling relations and fosters N spillover. This could lead to the development of new catalysts with enhanced activity due to the low N₂ activation energy barrier relatively weakly bound N.