Ruthenium based materials serve as more energy efficient catalysts for the dissociative chemisorption of nitrogen, the rate limiting step of ammonia synthesis via the Haber-Bosch process. Traditional iron-based catalysis reactors require higher temperatures and pressures than ruthenium systems, leading to higher energy costs for ammonia synthesis, a process that takes up approximately 2% of the world’s energy consumption. Despite the global importance of this chemical process, open questions remain concerning the dissipation of energy following N2 dissociation. Answering these questions may inform rational catalyst design and will enrich our understanding of fundamental surface dynamics. Using an ultra-high vacuum (UHV) experimental apparatus that combines a supersonic molecular beam with an in-line and in-situ scanning tunneling microscope (STM), we probe the dynamics of the N2/Ru(0001) system. The results of nitrogen adsorption on Ru(0001) is directly measured through STM imaging following doses from non-equilibrium distributions of energy- and angle-selected impinging N2 molecules. Atomic-scale local spatial resolution makes this instrumentation well suited to understanding the dynamic reactivity of N2 dissociation on Ru(0001) in an extremely low-coverage limit. The spatial distributions of N adatoms lend insight to the energy dissipation pathways such as energy transfer to phonons and electron hole-pair excitations following dissociative chemisorption. This work demonstrates the first STM images of N adsorbates on a metallic Ru(0001) surface resulting from nitrogen molecules with high translational kinetic energy.

Elucidating the reaction dynamics of dissociative chemisorption of nitrogen on Ru(0001)

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