Enhancing the nitrogen reduction activity of iron with inactive group-IVA elements at optimized stoichiometry

Artificial ammonia synthesis is dominated by the Haber-Bosch (HB) process at present. Recently, concerns of huge energy consumption and air pollution from the HB process have created an increasing demand for economical and eco-friendly NH3-synthesis approaches, such as electrocatalysis. Motivated by the fact that iron is widely used as a thermocatalyst in the HB process, we investigated bimetallic alloys consisting of Fe and group-IVA elements towards the electrochemical nitrogen reduction reaction (e-N2RR) via density functional theory calculations. Despite the inertness of pristine group-IVA elements towards the e-N2RR, alloying them with iron could surprisingly enhance the e-N2RR activity of iron. Moreover, we identified an optimal Fe-Si ratio (3 : 1) where a theoretical overpotential of only 0.21 V is observed, ranking among the best results ever. We also evaluated hydrogen evolution on Fe3Si and confirmed its low HER activity. Since most bimetallic alloys studied in this work have been synthesized, our work proposes a rational design for practical and economical e-N2RR electrocatalysts.