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.