Bulk and surface phases of iron oxides in an oxygen and water atmosphere at low pressure

Ketteler, Guido; Weiß, Werner; Ranke, Wolfgang; Schlögl, Robert

doi:10.1039/b009288f

Cited by 190 publications

(223 citation statements)

References 21 publications

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“…(reported in Figure 5 and in the Supplementary Information, respectively 35 Colloidal nanoparticles obtained by the decomposition of Fe(CO) 5 in the presence of pyridine N-oxide as oxidizer mainly composed of the wustite phase with small seeds of magnetite 26 were also reported, whereas under inert conditions low crystallinity wustite and maghemite domains were obtained. 40 In the sample obtained at longer growth time the XRD data indicate a peak sharpening due to the crystal growth, and that bcc-Fe is present together with wüstite and magnetite, the latter being the main phase.…”

Section: Crystal Structure and Phase Controlmentioning

confidence: 96%

“…The XRD spectrum, reported in Figure 5B, shows only the presence of a spinel phase, which could either correspond to the metastable phase of the ferric oxide γ- 35 due to the extra line broadening of the peaks the two nanocrystalline phases cannot be distinguished by X-Ray powder diffraction. Raman spectroscopy has been shown to be a powerful tool to investigate the structure of iron oxides and hydroxides.…”

Section: Structural Characterization and Phase Controlmentioning

confidence: 99%

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The Concept of Delayed Nucleation in Nanocrystal Growth Demonstrated for the Case of Iron Oxide Nanodisks

et al. 2006

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RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) TITLE RUNNING HEAD. Monodisperse Iron Oxide Nanodisks by Delayed Nucleation 2 ABSTRACT A comprehensive study of iron oxide nanocrystal growth through non-hydrolitic, surfactantmediated thermal reaction of iron pentacarbonyl and an oxidizer has been conducted, which includes size control, anisotropic shape evolution, and crystallographic phase transition of monodisperse iron oxide colloidal nanocrystals. The reaction was monitored by in situ UV-Vis spectroscopy taking advantage of the color change accompanying the iron oxide colloid formation allowing measurement of the induction time for nucleation. Features of the synthesis such as the size control and reproducibility are related to the occurrence of the observed delayed nucleation process. As a separate source of iron and oxygen is adopted, phase control could also be achieved by sequential injections of oxidizer.3

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Section: Crystal Structure and Phase Controlmentioning

confidence: 96%

Section: Structural Characterization and Phase Controlmentioning

confidence: 99%

The Concept of Delayed Nucleation in Nanocrystal Growth Demonstrated for the Case of Iron Oxide Nanodisks

et al. 2006

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“…5.1. However, as discussed in [225], an oxidation of the Fe-terminated Fe 3 O 4 (111) surface could also result in an O terminated structure by adsorption of an O monolayer and a rearrangement of the Fe cations. It would look similar to the O terminated FeO film surfaces described in Section 5.3 with its 3 Å surface periodicity.…”

Section: (I) Biphase Structures Formed Below T=1000 Kmentioning

confidence: 99%

“…The latter two phases have only been synthesized artificially, but all other phases occur also naturally. Under thermodynamic equilibrium, their stability ranges depend on the ambient O 2 gas pressure p(O 2 ) and on the temperature T. These stability ranges for pressures below 1 bar are shown in the phase diagram for the Fe-O system [225] depicted in Fig. 5.1.…”

Section: Oxydehydrogenation Of Ethylbenzene Over Carbon-based Catalystsmentioning

confidence: 99%

“…At intermediate oxidation pressures, both A and B terminations are observed with the A/B occupation ratio increasing continuously with p(O 2 ). Since this should not occur for an equilibrium phase transition between two phases (see the discussion in [225]), it must be a result of the reaction kinetics. pressures.…”

Section: (Ii) Termination B After Oxidation In 10 -5 Mbar Omentioning

confidence: 99%

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Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

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Metal-oxide based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elemantary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(111), Fe 3 O 4 (111) and α-Fe 2 O 3 (0001) films grown epitaxially on Pt(111) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorptiondesorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch reactor arrangement at high gas pressures and post reaction surface analysis, showed that only α-Fe 2 O 3 (0001) containing surface defects is catalytically active, whereas Fe 3 O 4 (111) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the "pressure-gap". A model is proposed according to which the active site involves a regular acidic surface sites and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields, such as environmental science, biophysics and chemical sensors.-2 -"2kyEi9FYSQjBVrZxIPQ.FHIAC_WRa02_review.doc", Datum: 19.02.03

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Ammonia Synthesis

Schlögl

2008

Handbook of Heterogeneous Catalysis

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phone +49 30 8413 4400, fax +49 30 8413 4401 2.1.5.5. The effect of the potassium promoter 2.1.6. Nitrogen chemisorption with polycrystalline substrates and at elevated pressures 2.1.6.1. Model studies 2.1.6.2. Polycrystalline substrates 2.1.7. The mechanism of ammonia synthesis 2.1.7.1. Basic kinetic information 2.1.7.2. Analytical rate equations 2.1.7.3. Microkinetic rate equations 2.1.8. Conclusion

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Bulk and surface phases of iron oxides in an oxygen and water atmosphere at low pressure

Cited by 190 publications

References 21 publications

The Concept of Delayed Nucleation in Nanocrystal Growth Demonstrated for the Case of Iron Oxide Nanodisks

The Concept of Delayed Nucleation in Nanocrystal Growth Demonstrated for the Case of Iron Oxide Nanodisks

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Ammonia Synthesis

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