Ammonia formation on hexagonal Molybdenum Nitride Surfaces using DFT with added van der Waals effects

It has been estimated that Ammonia production is responsible for 2% of world energy consumption. It is produced industrially by the reaction of H₂ and N₂ gases through Haber-Bosch catalytic reaction over Iron based catalysts which require extreme pressures and temperatures. Though, Ru-based catalysts involve milder conditions with more activity, they are ruled out due to high cost of Ru metal. In order to produce “greener ammonia”, development of efficient as well as cheap alternate catalysts is necessary. In recent years, scientific community has shown great interest in Molybdenum Nitride based materials as potential catalysts for Ammonia production.

Using Density Functional Theory (DFT), we studied the reaction steps involved in the production of Ammonia on Mo- and N- terminated hexagonal molybdenum nitride MoN(0001) surface. Adsorption characteristics of intermediates involved in the ammonia formation process are extensively studied. Using Climbing Image Nudged Elastic Band Method (CI-NEB), we identified possible routes for formation of NH₃ by both associative and dissociative mechanisms. Role of N ad-atom coverage on the surface in changing reaction barriers was also studied. Our work will form basis for the search of the most suitable catalyst for an important reaction.