Molecular scale investigations of the reactivity of magnetite with formic acid, pyridine, and carbon tetrachloride

Cutting, Richard S; Muryn, C. A.; Thornton, G.; Vaughan, David J.

doi:10.1016/j.gca.2006.04.034

Cited by 35 publications

(41 citation statements)

References 59 publications

(89 reference statements)

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“…Figure 43) [294]. The third termination observed by Cutting et al [304] appears similar to the honeycomb structure observed by Shimizu et al [107]. However, since this surface was found to be completely inert in adsorption experiments, Cutting et al [304] (111) surface is terminated by a single phase, and this must be borne in mind in the interpretation of data from area averaging techniques.…”

Section: How To Prepare and Recognise The Scv Surfacesupporting

confidence: 60%

“…The third termination observed by Cutting et al [304] appears similar to the honeycomb structure observed by Shimizu et al [107]. However, since this surface was found to be completely inert in adsorption experiments, Cutting et al [304] (111) surface is terminated by a single phase, and this must be borne in mind in the interpretation of data from area averaging techniques. Moreover, other than the Fe tet1 termination, the structure of the other frequently observed terminations has not been determined using quantitative structural techniques, and further work is needed to establish the details of the Fe oct2 termination.…”

Section: How To Prepare and Recognise The Scv Surfacesupporting

confidence: 55%

“…As discussed above, these conditions are reducing, and lead to multiple surface structures on Fe 3 O 4 (111). Three different, coexisting terminations were observed in STM images [304], and each interacted differently with HCOOH. However, it is important to note that the interpretation of the STM images relies heavily on the surface model assumed.…”

Section: Formic Acid (Hcooh)mentioning

confidence: 98%

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Iron oxide surfaces

Parkinson

2016

Surface Science Reports

483

463

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The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), hematite (α-Fe 2 O 3 ), and wüstite (Fe 1-x O) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe 3 O 4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment, and because it is an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed.The best understood iron oxide surface at present is probably Fe 3 O 4 (100); the structure is known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Fe oct -O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10 Such straightforward preparation of a monophase termination is generally not the case for other iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe (0001) is the most studied hematite surface, but 2 difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe 3 O 4 (111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe 1-x O and α-Fe 2 O 3 (0001) islands was recently challenged and a new structure based on a thin film of Fe 3 O 4 (111) on α-Fe 2 O 3 (0001) was proposed. The merits of the compet...

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Section: How To Prepare and Recognise The Scv Surfacesupporting

confidence: 60%

Section: How To Prepare and Recognise The Scv Surfacesupporting

confidence: 55%

Section: Formic Acid (Hcooh)mentioning

confidence: 98%

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Iron oxide surfaces

Parkinson

2016

Surface Science Reports

483

463

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“…Under the conditions typically used in temperature programmed desorption/reaction (TPD, TPR) studies, the FeO films were essentially inert towards molecular adsorption (carbon monoxide, water, ethylbenzene and styrene). Therefore, the adsorption studies were primarily focused on surfaces of magnetite (Fe 3 O 4 ) and hematite (Fe 2 O 3 ) (see also [19,20]). …”

Section: Introductionmentioning

confidence: 99%

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Sun

Qin

Lewandowski

et al. 2009

Journal of Catalysis

221

236

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Abstract. CO oxidation on a clean Pt(111) single crystal and thin iron oxide films grown on Pt(111) was studied at different CO:O 2 ratios (between 1:5 and 5:1) and partial pressures up to 60 mbar at 400 -450 K. Structural characterization of the model catalysts was performed by scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy and temperature programmed desorption. It is found that monolayer FeO (111) films grown on Pt(111) are much more active than clean Pt(111) and nm-thick Fe 3 O 4 (111) films at all reaction conditions studied. Post-characterization of the catalysts revealed that at CO:O 2 >1 the FeO(111) film dewets the Pt surface with time, ultimately resulting in highly dispersed iron oxide particles on Pt(111). The film dewetting was monitored in situ by polarisation-modulated infrared reflection absorption spectroscopy. The reaction rate at 450 K exhibited first order for O 2 and non-monotonously depended on CO pressure. In O 2 -rich ambient the films were enriched with oxygen while maintaining the long range ordering.Based on the structure-reactivity relationships observed for the FeO/Pt films, we propose that the reaction proceeds through the formation of a well-ordered, oxygen-rich FeO x (1 < x < 2) film that reacts with CO through the redox mechanism. The reaction induced dewetting in fact deactivates the catalyst. The results may aid in our deeper understanding of reactivity of metal particles encapsulated by thin oxide films as a result of strong metal support interaction.

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“…[33] The formation of dichlorocarbene (CCl 2 ) at the surface has been proven by adsorption of CCl 4 on Fe 3 O 4 studied by STM. [34] Moreover, it was found that the CCl 2 fragment is mobile on the surface at 298 K. Koper et al found from pulse experiments that CHCl 3 is initially converted on CaO into CO exclusively, whereas the addition of larger amounts resulted in the formation of COCl 2 and C 2 Cl 4 . Hydration of CaO led to the formation of COCl 2 and C 2 Cl 4 after the introduction of lower amounts of CHCl 3 .…”

mentioning

confidence: 99%

Intermediates in the Destruction of Chlorinated C₁ Hydrocarbons on La‐Based Materials: Mechanistic Implications

Heijden

Ramos

Weckhuysen

2007

Chemistry A European J

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Activity experiments using GC analysis of reactor effluent have been combined with in situ IR spectroscopy to elucidate the reaction steps in the destructive adsorption of CHCl3, CH2Cl2, and CH3Cl over LaOCl. The IR results show that during reaction, LaOCl is covered with carbonate, formate, and methoxy groups. The relative amount of each of these surface intermediates depends on the Cl/H ratio of the reactant. The decomposition of the surface species leads to formation of the reaction products, and is influenced by the temperature and the relative amount of Cl present on the surface. The GC results show that the activity for the destructive adsorption of H‐containing chlorinated C1 compounds decreases with increasing hydrogen content of the reactant. The acquired insight into the mechanism of destructive adsorption is crucial to the design of new catalyst materials for the efficient conversion of chlorinated hydrocarbons into nonhazardous products or reusable chemicals.

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Molecular scale investigations of the reactivity of magnetite with formic acid, pyridine, and carbon tetrachloride

Cited by 35 publications

References 59 publications

Iron oxide surfaces

Iron oxide surfaces

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Intermediates in the Destruction of Chlorinated C₁ Hydrocarbons on La‐Based Materials: Mechanistic Implications

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Molecular scale investigations of the reactivity of magnetite with formic acid, pyridine, and carbon tetrachloride

Cited by 35 publications

References 59 publications

Iron oxide surfaces

Iron oxide surfaces

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Intermediates in the Destruction of Chlorinated C1 Hydrocarbons on La‐Based Materials: Mechanistic Implications

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Intermediates in the Destruction of Chlorinated C₁ Hydrocarbons on La‐Based Materials: Mechanistic Implications