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Updated: Mar 26, 2026

Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
On the origin of high activity of hcp metals for ammonia synthesis
Shideh Ahmadi1, Payam Kaghazchi1
1Physical and Theoretical Chemistry, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany. payam.kaghazchi@fu-berlin.de.
Abstract:
Structure and activity of nanoparticles of hexagonal close-packed (hcp) metals are studied using first-principles calculations. Results show that, in contact with a nitrogen environment, high-index {134[combining macron]2} facets are formed on hcp metal nanoparticles. Nitrogen molecules dissociate easily at kink sites on these high-index facets (activation barriers of <0.2 eV). Analysis of the site blocking effect and adsorption energies on {134[combining macron]2} facets explains the order of activity of hcp metals for ammonia synthesis: Re < Os < Ru. Our results indicate that the high activity of hcp metals for ammonia synthesis is due to the N-induced formation of {134[combining macron]2} facets with high activity for the dissociation of nitrogen molecules. However, quite different behavior for adsorption of dissociated N atoms leads to distinctive activity of hcp metals.
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