Engaging the Concepts of Bimetallicity and Mechanical Strain for N₂ Activation: A Computational Exploration

N₂ activation is a vital step in the process toward NH₃ production. NH₃ synthesis has been considered a crucial process for the production of value-added chemicals and/or hydrogen carriers over recent years. In this work, density functional theory (ab initio) calculations are implemented for a thorough screening of bimetallic alloy surfaces using Fe, Ru, and Mo as the matrix (host) metals and Ag, Au, Co, Cu, Fe, Mo, Ni, Pd, Pt, Rh, and Rh as heterometals toward exploring the N₂ catalytic activation (electronic and chemical characteristics); the monometallic surfaces are used for critical comparison in terms of their N₂ activation behavior. In particular, adsorption geometries/energetics, density of states (DOS), and charge transfer are discussed. From the N₂ activation on the surfaces, we could precisely capture the transition state of the N₂ dissociation reaction/step. The effect of the metal alloying (geometrical and electronic factors) as well as the effect of applied mechanical strain, as a tuning factor of alloying, are both studied and thoroughly discussed. DOS studies revealed that the d-band center moved toward the negative direction for all late-TM-based alloys, thereby allowing the nitrogen molecule to adsorb weakly as compared to the early-TM surface alloys. In terms of the mechanical strain, for most of the alloy surfaces studied, apart from the Mo/Fe(110) one, the N₂ binding energy varies as a linear function of the applied strain. The mechanical effect trend is in agreement with the charge transfer descending order followed: Fe/Mo(110) > Rh/Mo(110) > Au/Mo(110) > Pt/Mo(110) > Ni/Mo(110) > Ru/Mo(110) > Cu/Mo(110) > Ag/Mo(110) > Pd/Mo(110) > Au/Mo(110), pointing out that Fe-functionalized Mo(110) surface presents the highest charge transfer of -2.14 |e| to the N₂ molecule. This study aspires to provide navigation criteria through the abundant design criteria of N₂ activation catalysts.