One rational approach to improve the ammonia synthesis rate is using bimetallic nanoalloys catalysts containing a metal that can easily dissociate the N₂ molecule and a metal with a low binding energy to N atoms. Such is the case of FeRu nanoalloy catalyst with HCP structure that exhibited a higher catalytic efficiency for NH₃ synthesis than the monometallic, Fe and Ru, catalysts. However, considering the amount of the precious metal, Ru, the activity of the FeRu catalyst is not high enough to make it commercially attractive. In this work, low containing Ru FeRu alloy with BCC structure is investigated for its physicochemical properties towards the NH₃ synthesis. Spin-polarized periodic plane-wave calculations were performed on pristine Fe and Ru containing Fe slabs (6% Ru at the surface). The position of Ru is thermodynamically favored at the surface, and doubling up the amount of Ru led to the same conclusion. The presence of Ru in the Fe slab leads to an increase in the slab stability approximated by the cohesive energy. In agreement with the work function difference between Ru and Fe, the Ru atom gains 0.54 electrons, which may help to promote the electron donation from Ru to the π-orbitals of the N₂ triple bond. In Fig. 1a the density of states (DOS) profiles of the Ru atom in the FeRu slab is compared to a Ru atom in the surface of HCP-Ru(0001) and BCC-Ru(110). From the DOS profiles, the Ru atom in the alloy shows similarities with the Ru atoms in the HCP and BCC surfaces. However, near the Fermi level, the resemblances are closer to the BCC than HCP-Ru atoms. These changes in the electronic properties affected the adsorption and dissociation energies of the N₂. The most stable configurations of the N₂ adsorption and dissociation on pristine Fe, pristine Ru, and FeRu are shown in Fig. 1b. More details about the effect of Ru on the charge transfer, vibrational modes, and activation energies will be given during the presentation.

Dr. David Samuel Rivera Rocabado

Assistant Professor, Yokohama City University

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