Density Functional Theory and Kinetic Studies of Methanation on Iron Surface

Lo, John M. H.; Ziegler, Tom

doi:10.1021/jp0722206

Cited by 54 publications

(68 citation statements)

References 78 publications

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“…22 Previous calculations have revealed that this size of k-point mesh is already able to yield the lattice constant and energy comparable to those obtained using a denser 12 × 12 × 12 mesh. 12 The corresponding bulk modulus (156 GPa) and magnetic moment (2.30 µ 0 ) also show a good agreement with experiments (170 GPa 23 and 2.22 µ 0 , 24 respectively). Adsorption of molecules was allowed on only one side of the slab; therefore, a 10 Å vacuum layer was inserted between two replicas to minimize the induced dipole-dipole interactions.…”

Section: Theoretical Methodssupporting

confidence: 76%

“…In spite of that the associated barriers are higher (∼30 kcal/mol), these processes are more statistically feasible as the involved species have the highest surface concentrations during the course of the F-T synthesis. 12,14 Having determined the most probable C-C bond propagation step, the kinetic profile connecting the precursors CCCH 2 and CCCH 3 and the products (i.e., propylene and propane) was calculated. The resulting energy profile suggested that the most stable C 3 species is CCCH 3 when lateral interaction between coadsorbed species is taken into account.…”

Section: Discussionmentioning

confidence: 99%

“…This gives rise to the resulting reaction barrier close to that for the surface hydrogen diffusion on Fe(100). 12 Hydrogenation of Allylic C 3 H 5 . Both forms of allyl can be transformed into propylene via the hydrogen addition at either of the terminal C atoms.…”

Section: Hydrogenation Of C 3 Hmentioning

confidence: 99%

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A First-Principle Study of Chain Propagation Steps in the Fischer−Tropsch Synthesis on Fe(100)

Ziegler

2008

J. Phys. Chem. C

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We presented density functional theory based calculations on the formation and reactivity of C 3 species produced from CO and H 2 over Fe(100). The results indicated that the conversion of syngas to propylene and propane is overall exothermic, and the most stable C 3 surface species are CCCH 2 and CCCH 3 . It was found that the chain propagation on Fe (100) is initiated by the recombination of C and CCCH 2 /CCCH 3 rather than by the coupling reaction of surface vinyl and methylene. The potential energy surface associated with such an alkynyl mechanism has been computed and validated. Furthermore, this alkynyl mechanism has been compared to the conventional alkenyl mechanism in explaining the experimental observations of the 13 C 2 H 4 -probed polymerization over Fe. It was finally found that the two propylene isotopomers observed experimentally in the product mixture are produced from surface ethylene along different reaction paths rather than the isomerization of surface allyl.

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Section: Theoretical Methodssupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

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A First-Principle Study of Chain Propagation Steps in the Fischer−Tropsch Synthesis on Fe(100)

Ziegler

2008

J. Phys. Chem. C

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“…Furthermore, we computed two adsorption configurations for (H 2 O) 8 9 t1 with fused five-membered and six-membered rings and (H 2 O) 9 -t2 with three exocyclic H 2 O molecules perfectly remotely located around the six-membered ring without Hbonding. The first one has lower adsorption energy than the second one (−5.67 vs −6.00 eV), indicating that the structure with only a six-membered ring is more stable than that with fused five-and six-membered rings.…”

Section: Introductionmentioning

confidence: 99%

Coverage Dependent Water Dissociative Adsorption on the Clean and O-Precovered Fe(111) Surfaces

et al. 2015

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Water dissociative adsorption on the clean and Oprecovered Fe(111) surfaces at different coverage have been studied using the density functional theory method (GGA-PBE) and ab initio atomistic thermodynamics. On the clean p(3 × 3) Fe (111) surface, surface H, O, OH, and H 2 O species can migrate easily. Considering adsorption and H-bonding, the adsorbed H 2 O molecules can be dispersed or aggregated in close energies at low coverage, while in different aggregations at high coverage, indicating that the adsorbed H 2 O molecules might not have defined structures, as observed experimentally. On the O-precovered surface (n O = 1−8), the first dissociation step, nO + H 2 O = (n − 1)O + 2OH, has a very low barrier and is reversible; and the barriers of the sequential OH dissociation steps, (n − 1)O + 2OH = nO + H + OH and nO + H + OH = (n + 1)O + 2H, are close (0.9−1.2 eV). All of these barriers are coverage independent. For OH and H adsorption at 1/3 ML coverage, surface OH forms a trimer (OH) 3 unit, and surface O forms a regular linear pattern. At one ML coverage, there are three dispersed (OH) 3 units for OH adsorption and three well-ordered parallel lines for O adsorption. The average adsorption energies for OH and O adsorption are coverage independent. Desorption temperatures of H 2 O and H 2 under ultrahigh vacuum conditions are computed. Systematic comparison among the Fe(110), Fe(100), and Fe (111) surfaces reveal their intrinsic differences in water dissociative adsorption and provide a basic understanding of water-involved reactions catalyzed by iron and interaction mechanisms of water interaction with metal surfaces.

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“…Iron is a common and useful element, and its characteristics have been studied by many researchers, such as magnetic property, surface oxidation [1] and model catalyst [2]. For theoretical study, Eder et al [3] presented first-principles analysis of initial stages of iron-oxidation caused by water on iron surfaces.…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Study Of The Interaction Of Hydroxyl Groups With Iron Surface

Nunomura

Sunada

2015

Archives of Metallurgy and Materials

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The electronic interaction of hydroxyl groups with Fe(100) surface is modelled using a density functional theory (DFT) approach. The adsorption energies and structures of possible adsorption sites are calculated. According to our calculations of the adsorption energies, the interaction between oxygen atom of OH species and surface iron atom is shown to be strong. It is likely to be due to the interaction of the lone-pair electrons of oxygen and the 3d orbital electrons of iron atom. At low coverage (0.25ML), the most favorable adsorption sites are found to be two-fold bridge sites, and the orientation of the O-H bond is tilted to the surface normal. Further, the adsorption energy is found to be decreasing with the increasing OH group coverage.Keywords: density functional theory, hydroxyl groups, iron surface, adsorption energy Wzajemne oddziaływanie elektronowe grup hydroksylowych na powierzchni Fe(100) modelowano stosując metodę teorii funkcjonału gęstości (ang. density functional theory; DFT). Dokonano obliczeń energii adsorpcji oraz struktury potencjalnych centrów adsorpcji. Na podstawie otrzymanych wyników stwierdzono, że pomiędzy atomem tlenu grupy OH, a powierzchnią atomu żelaza występuje silne oddziaływanie. Jest to prawdopodobnie spowodowane oddziaływaniem wolnej pary elektronowej tlenu z elektronami atomu żelaza na orbitalach 3d. Przy niskim poziomie pokrycia (0,25 ML), najbardziej uprzywilejowane centra aktywne stanowią podwójne pozycje mostkowe, a orientacja wiązania O-H jest prostopadła do powierzchni. Ponadto energia adsorpcji zmniejsza się wraz ze wzrostem ilości grup OH na powierzchni.

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Density Functional Theory and Kinetic Studies of Methanation on Iron Surface

Cited by 54 publications

References 78 publications

A First-Principle Study of Chain Propagation Steps in the Fischer−Tropsch Synthesis on Fe(100)

A First-Principle Study of Chain Propagation Steps in the Fischer−Tropsch Synthesis on Fe(100)

Coverage Dependent Water Dissociative Adsorption on the Clean and O-Precovered Fe(111) Surfaces

Density Functional Theory Study Of The Interaction Of Hydroxyl Groups With Iron Surface

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