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Coverage-Dependent Adsorption of Hydrogen on Fe(100): Determining Catalytically Relevant Surface Structures via Lattice Gas Models
journal contribution
posted on 2020-03-18, 20:18 authored by Alyssa J. R. Hensley, Greg Collinge, Yong Wang, Jean-Sabin McEwenHydrogen
adatoms are a critical surface species for several reactions
catalyzed by Fe surfaces such as Fischer–Tropsch synthesis,
ammonia synthesis, and the hydrodeoxygenation of biomass-derived oxygenates.
Parameterizing the energetics for H/Fe in terms of both coverage and
configuration space can significantly aid in the development of multiscale
models as well as provide atomic level insight into the dominant surface
structures present under realistic reaction conditions. Here, we construct
a lattice gas model for H/Fe(100), where the lateral interactions
are determined from first-principles using density functional theory.
Using 950 symmetrically unique H/Fe(100) configurations, we generate
a cluster expansion with a predictive accuracy in terms of surface
energy of 3.8 meV/site over a coverage range from 0 to 3 monolayers.
Ten electronic ground state structures are identified from this thorough
scan (including the structures at 0 and 3 monolayers), which were
subsequently used to generate ab initio phase diagrams
under a range of temperatures and pressures. Under reaction conditions
typical of Fischer–Tropsch synthesis, ammonia synthesis, and
biomass oxygenate hydrodeoxygenation, we find that the 1.0 monolayer
structure is dominant. Furthermore, examination of the total H–H
lateral interactions for the H/Fe(100) electronic ground state structures
shows that H/Fe(100) can be accurately modeled via a mean-field ideal
lattice gas model for coverages less than 1.0 monolayers. Overall,
this work enables the incorporation of H–H lateral interactions
on Fe(100) into multiscale models, via either mean-field or site-dependent
techniques, and provides atomic insight into the catalytically relevant
H/Fe(100) structures for a range of heterogeneous reactions.