Theoretical Insight into the Special Synergy of Bimetallic Site in Co/MoC Catalyst to Promote N₂-to-NH₃ Conversion

The catalytic mechanisms of nitrogen reduction reaction (NRR) on the pristine and Co/alpha-MoC(001) surfaces were explored by density functional theory calculations. The results show that the preferred pathway is that a direct N equivalent to N cleavage occurs first, followed by continuous hydrogenations. The production of second NH3 molecule is identified as the rate-limiting step on both systems with kinetic barriers of 1.5 and 2.0 eV, respectively, indicating that N-2-to-NH3 transformation on bimetallic surface is more likely to occur. The two components of the bimetallic center play different roles during NRR process, in which Co atom does not directly participate in the binding of intermediates, but primarily serves as a reservoir of H atoms. This special synergy makes Co/alpha-MoC(001) have superior activity for ammonia synthesis. The introduction of Co not only facilitates N-2 dissociation, but also accelerates the migration of H atom due to the antibonding characteristic of Co-H bond. This study offers a facile strategy for the rational design and development of efficient catalysts for ammonia synthesis and other reactions involving the hydrogenation processes.