TY - JOUR
T1 - First-Principles Insights into the Thermocatalytic Cracking of Ammonia-Hydrogen Blends on Fe(110)
T2 - 1. Thermodynamics
AU - Martirez, J. Mark P.
AU - Carter, Emily A.
N1 - Funding Information:
E.A.C. acknowledges the support from the Air Force Office of Scientific Research (AFOSR) via the Department of Defense Multidisciplinary University Research Initiative (MURI) under AFOSR Award No. FA9550-15-1-0022 and the University of California, Los Angeles. E.A.C. thanks the High Performance Computing Modernization Program (HPCMP) of the U.S. Department of Defense and Princeton University’s Terascale Infrastructure for Groundbreaking Research in Engineering and Science (TIGRESS) for providing the computational resources.
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/11/24
Y1 - 2022/11/24
N2 - Ammonia (NH3) is being considered as a practical means to transport hydrogen (H2) because of its higher volumetric energy density for the same temperature and pressure. Thermodynamics suggest high temperature is needed to decompose NH3to nitrogen (N2) and H2. Furthermore, overcoming decomposition kinetic barriers requires a catalyst. Via density functional theory, we study this reaction on a model catalyst: the close-packed (110) facet of α-Fe. Specifically, we predict detailed in-operando temperature- and pressure-dependent surface phase diagrams on this benchmark catalyst that offer insights for the design of optimal NH3decomposition catalysts. Here, we explore the equilibrium composition(s) of the Fe(110) surface when exposed to NH3-H2mixtures. We predict that both N and NH partially cover the Fe(110) surface at 300-400 °C (far above the NH3decomposition-formation coexistence temperature at standard partial pressures of 1 bar: ∼180 °C) and 2-4 bar of total reactor pressure. At the equilibrium N/NH coverage, these species inhibit coadsorption of H, indicating that direct H2production may occur. However, from thermodynamics alone, removal of N/NH as N2(g) is extremely unfavorable even at these elevated temperatures-effectively deactivating the surface toward further NH3decomposition.
AB - Ammonia (NH3) is being considered as a practical means to transport hydrogen (H2) because of its higher volumetric energy density for the same temperature and pressure. Thermodynamics suggest high temperature is needed to decompose NH3to nitrogen (N2) and H2. Furthermore, overcoming decomposition kinetic barriers requires a catalyst. Via density functional theory, we study this reaction on a model catalyst: the close-packed (110) facet of α-Fe. Specifically, we predict detailed in-operando temperature- and pressure-dependent surface phase diagrams on this benchmark catalyst that offer insights for the design of optimal NH3decomposition catalysts. Here, we explore the equilibrium composition(s) of the Fe(110) surface when exposed to NH3-H2mixtures. We predict that both N and NH partially cover the Fe(110) surface at 300-400 °C (far above the NH3decomposition-formation coexistence temperature at standard partial pressures of 1 bar: ∼180 °C) and 2-4 bar of total reactor pressure. At the equilibrium N/NH coverage, these species inhibit coadsorption of H, indicating that direct H2production may occur. However, from thermodynamics alone, removal of N/NH as N2(g) is extremely unfavorable even at these elevated temperatures-effectively deactivating the surface toward further NH3decomposition.
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U2 - 10.1021/acs.jpcc.2c06003
DO - 10.1021/acs.jpcc.2c06003
M3 - Article
AN - SCOPUS:85141958838
SN - 1932-7447
VL - 126
SP - 19733
EP - 19744
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 46
ER -