Highly Efficient Ni-Doped Iron Catalyst for Ammonia Synthesis from Quantum-Mechanics-Based Hierarchical High-Throughput Catalyst Screening

To discover more efficient industrial catalysts for ammonia synthesis via the Haber-Bosch (HB) process, we employed quantum mechanics (QM)-based hierarchical high-throughput catalyst screening (HHTCS) to test a wide group of elements (34) as candidates to dope the Fe(111) catalyst subsurface. The QM free-energy reaction network of HB over Fe(111) yields ten barriers as potentially rate-determining, of which we select four as prototypical, arrange them hierarchically, and define a corresponding set of screening criteria, which we then use to screen candidate catalysts. This leads to two promising candidates (Co and Ni), from which we selected the most promising (Ni) for a complete QM and kinetic study. The kinetic Monte Carlo (kMC) simulations predict a 16-fold increase in HB turn-over frequency (TOF) for the Ni-doped catalyst compared to the pure Fe(111) surface under realistic conditions. The 16-fold increase in HB TOF is a significant improvement and may trigger future experimental studies to validate our prediction. This TOF improvement could lead to similar reaction rates as with pure Fe but at a reaction temperature decreased by 100° from 773 to 673 K and a total reactant pressure decreased by 6 times from 201 to 34 atm. We interpret the reasons underlying this improvement using valence bond and kinetic analyses. We suggest this Ni-doped Fe(111) catalyst as a candidate to reduce the world energy consumption for the HB process while satisfying future needs for energy and environment.