Oxygen-Induced Transformations of an FeO(111) Film on Pt(111): A Combined DFT and STM Study

Giordano, Livia; Lewandowski, Mikołaj; Groot, Irene M. N.; Sun, Ying-Na; Goniakowski, Jacek; Noguera, Claudine; Shaikhutdinov, Shamil K.; Pacchioni, Gianfranco; Freund, Hans‐Joachim

doi:10.1021/jp1070105

Cited by 95 publications

(157 citation statements)

References 44 publications

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“…The trilayer islands reported here show strong similarities with structures formed by oxidation of FeO thin films on both Pd(111) and Pt(111), which have been studied and described in a number of previous publications [28][29][30] , however with several notable differences. On both Pt(111) and Pd(111) the formation of an O-Fe-O trilayer takes place in specific domains of the moiré structure, and hence does not convert the complete metal oxide sheet, as we observe for cobalt oxide on Au(111).…”

Section: Hydroxyl Overlayersupporting

confidence: 69%

Gold-supported two-dimensional cobalt oxyhydroxide (CoOOH) and multilayer cobalt oxide islands

Fester

Walton

et al. 2017

Phys. Chem. Chem. Phys.

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In the present study, we investigate the facile conversion of Co-O bilayer islands on a Au(111) surface into preferentially O-Co-O trilayers in an oxygen atmosphere and O-Co-O-Co-O multilayers at elevated temperature. We characterize and compare the island morphologies with Scanning Tunneling Microscopy, X-ray photoemission spectroscopy (XPS) and valence band spectroscopy, and show that the cobalt oxidation state changes from Co 2+ in bilayers to purely Co 3+ in trilayers and a mixture of Co 2+ and Co 3+ in the multilayer morphology. In contrast to bilayers and multilayers, the trilayer structure appears to grow pseudomorphic with the Au(111) substrate, and in addition we reveal the presence of a hydroxyl overlayer on this island type as evidenced by the appearance of a √3 × √3 30° superstructure in STM correlated with the fingerprints of OH species in XPS and valence band spectroscopy. The obtained layered morphology consisting of hydroxylated trilayer islands is identical to an exfoliated sheet of the -CoOOH which is proposed to be the active phase of the cobalt oxide oxygen evolution reaction catalyst present in the electrochemical environment, and we note that this synthesized structure thus could serve as a valuable model catalyst.

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Section: Hydroxyl Overlayersupporting

confidence: 69%

Gold-supported two-dimensional cobalt oxyhydroxide (CoOOH) and multilayer cobalt oxide islands

Fester

Walton

et al. 2017

Phys. Chem. Chem. Phys.

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“…470 K, when oxidizing a full monolayer FeO film on Pt(111). 34,37 In the present work, the high dispersion and small size of FeO nanoislands at the submonolayer FeO 1Àx /Pt(111) surfaces may be attributed to the easy occurrence of the oxidation-induced structural transformation. It is interesting to point out that the FeO 2Àx surface can be reduced back to the FeO 1Àx surface through UHV annealing.…”

Section: Resultsmentioning

confidence: 51%

Reversible structural transformation of FeOx nanostructures on Pt under cycling redox conditions and its effect on oxidation catalysis

Yao

Guo

et al. 2013

Phys. Chem. Chem. Phys.

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a Understanding dynamic changes of catalytically active nanostructures under reaction conditions is a pivotal challenge in catalysis research, which has been extensively addressed in metal nanoparticles but is less explored in supported oxide nanocatalysts. Here, structural changes of iron oxide (FeO x ) nanostructures supported on Pt in a gaseous environment were examined by scanning tunneling microscopy, ambient pressure X-ray photoelectron spectroscopy, and in situ X-ray absorption spectroscopy using both model systems and real catalysts. O-Fe (FeO) bilayer nanostructures can be stabilized on Pt surfaces in reductive environments such as vacuum conditions and H 2 -rich reaction gas, which are highly active for low temperature CO oxidation. In contrast, exposure to H 2 -free oxidative gases produces a less active O-Fe-O (FeO 2 ) trilayer structure. Reversible transformation between the FeO bilayer and FeO 2 trilayer structures can be achieved under alternating reduction and oxidation conditions, leading to oscillation in the catalytic oxidation performance.

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“…A fascinating recent development came with the discovery that under strongly oxidising conditions the FeO monolayer can be transformed to a O-Fe-O (i.e. FeO 2 ) trilayer structure [388]. This unusual iron oxide has no bulk counterpart and is stabilized by the interaction with the substrate.…”

Section: Wüstite (Fe 1-x O) Surfacesmentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

499

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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Oxygen-Induced Transformations of an FeO(111) Film on Pt(111): A Combined DFT and STM Study

Cited by 95 publications

References 44 publications

Gold-supported two-dimensional cobalt oxyhydroxide (CoOOH) and multilayer cobalt oxide islands

Gold-supported two-dimensional cobalt oxyhydroxide (CoOOH) and multilayer cobalt oxide islands

Reversible structural transformation of FeOx nanostructures on Pt under cycling redox conditions and its effect on oxidation catalysis

Iron oxide surfaces

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