A DFT study of the hematite surface state in the presence of H2, H2O and O2

Souvi, Sidi; Badawi, Michaël; Paul, Jean‐François; Cristol, Sylvain; Cantrel, Laurent

doi:10.1016/j.susc.2012.12.012

Cited by 48 publications

(32 citation statements)

References 35 publications

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“…A number of DFT studies have been dedicated to examination of hematite’s bulk and surface properties. 20, 25–26, 46–48 Souvi et al . reported a detailed analysis of the α-Fe 2 O 3 adsorption thermodynamics in the presence of O 2 , H 2 O, and H 2 gases.…”

Section: Resultsmentioning

confidence: 99%

Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

et al. 2016

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The atomic-scale reduction mechanism of α-Fe2O3 nanowires by H2 was followed using transmission electron microscopy to reveal the evolution of atomic structures and the associated transformation pathways for different iron oxides. The reduction commences with the generation of oxygen vacancies that order onto every 10th (303false¯0) plane. This vacancy ordering is followed by an allotropic transformation of α-Fe2O3 → γ-Fe2O3 along with the formation of Fe3O4 nanoparticles on the surface of the γ-Fe2O3 nanowire by a topotactic transformation process, which shows 3D correspondence between the structures of the product and its host. These observations demonstrate that the partial reduction of α-Fe2O3 nanowires results in the formation of a unique hierarchical structure of hybrid oxides consisting of the parent oxide phase, γ-Fe2O3, as the one-dimensional wire and the Fe3O4 in the form of nanoparticles decorated on the parent oxide skeleton. We show that the proposed mechanism is consistent with previously published and our density functional theory results on the thermodynamics of surface termination and oxygen vacancy formation in α-Fe2O3. Compared to previous reports of α-Fe2O3 directly transformed to Fe3O4, our work provides a more in-depth understanding with substeps of reduction, i.e., the whole reduction process follows: α-Fe2O3 → α-Fe2O3 superlattice → γ-Fe2O3 + Fe3O4→ Fe3O4.

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Section: Resultsmentioning

confidence: 99%

Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

et al. 2016

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“…They were followed by several DFT+U studies. Souvi et al [13] found that first water molecule is adsorbed dissociatively, while second and third water adsorb associatively. Calculations of low-coverage water adsorption and dissociation on various surface terminations ofα-Fe 2 O 3 (0001) performed by Nguyen et al [14] revealed very low energy barriers (0.06-0.3 eV) for water dissociation.…”

Section: Introductionmentioning

confidence: 99%

Incipient adsorption of water and hydroxyl on hematite (0001) surface

Pabisiak

Kiejna

2019

J. Phys. Commun.

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The adsorption of submonolayer coverages of water and hydroxyl molecules on hematite (0001) surface is investigated using density functional theory with Hubbard correction U (DFT+U). The effect of adsorption on the structural, energetic, and electronic properties of both iron and oxygen terminated hematite surfaces is examined. The influence of the van der Waals interactions on the adsorption binding energy and geometry is also considered. It is found that tilted orientations of molecules are energetically more favored than planar ones, because the hydrogen bond stabilizes molecules on the surface. Bonding of H 2 O is more than twice weaker than that of OH. For both molecules adsorption on the iron-rich termination is much stronger than on the oxygen-terminated surface. The differences in bonding properties of water and hydroxyl molecules to the hematite surfaces are explained by different character of the charge transfer in the molecule-oxide system.

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“…5 The computational results also disagree with each other. [7][8][9][10][11] Density functional theory (DFT) within the generalised gradient approximation (GGA) has shown that the Fe-terminated surface of hematite is preferred at low oxygen pressures and that O-terminated surfaces should occur at increasing oxygen chemical potentials (m O ), leaving a small stability domain to ferryl-terminated surfaces. [7][8][9] Inclusion of a Hubbard-type on-site Coulomb repulsion (GGA+U approach) yields a ferryl-terminated surface at high m O and Fe-terminated surfaces at low potentials.…”

Section: Introductionmentioning

confidence: 99%

Water adsorption and O-defect formation on Fe₂O₃(0001) surfaces

Ovcharenko

Voloshina

Sauer

2016

Phys. Chem. Chem. Phys.

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The stability and reactivity of the hematite, FeO(0001) surface are studied by density functional theory including an on-site Coulomb term (DFT+U). Even under oxygen rich conditions, the metal-terminated surface is shown to be stable. On this surface termination, the isolated water molecule forms a heterolytically dissociated structure with the OH group attached to a surface Fe ion and the proton to a surface O ion. Dissociative adsorption is strongly enhanced at oxygen vacancy sites. Here, the OH group fills the oxygen vacancy site. Dehydrogenation accompanied by defect healing is favoured compared to water desorption (178 kJ mol compared to 236 kJ mol). The water adsorption energies (at 0 K) for the clean and defective surfaces are 100 kJ mol and 288 kJ mol, respectively.

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A DFT study of the hematite surface state in the presence of H2, H2O and O2

Cited by 48 publications

References 35 publications

Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

Incipient adsorption of water and hydroxyl on hematite (0001) surface

Water adsorption and O-defect formation on Fe₂O₃(0001) surfaces

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A DFT study of the hematite surface state in the presence of H2, H2O and O2

Cited by 48 publications

References 35 publications

Atomic Structural Evolution during the Reduction of α-Fe2O3 Nanowires

Atomic Structural Evolution during the Reduction of α-Fe2O3 Nanowires

Incipient adsorption of water and hydroxyl on hematite (0001) surface

Water adsorption and O-defect formation on Fe2O3(0001) surfaces

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Product

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Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

Atomic Structural Evolution during the Reduction of α-Fe₂O₃ Nanowires

Water adsorption and O-defect formation on Fe₂O₃(0001) surfaces