Oxidation of Ultrathin FeO(111) Grown on Pt(111): Spectroscopic Evidence for Hydroxylation

Johansson, Niclas; Merte, Lindsay R.; Grånäs, Elin; Wendt, Stefan; Andersen, Jesper N; Schnadt, Joachim; Knudsen, Jan

doi:10.1007/s11244-015-0521-7

Cited by 25 publications

(39 citation statements)

References 55 publications

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“…We speculate that this hydroxylation arises from a particularly high affinity of trilayers compared to bilayers and multilayers towards H 2 O or H 2 dissociative adsorption, even taking place in the rest gas of UHV. This observation is in line with recently reported results on the facile hydroxylation of FeO 2 trilayers 25 .…”

Section: Hydroxyl Overlayersupporting

confidence: 94%

“…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). As found in the present study, a √3 x√3 30° superstructure was also observed on the oxidized patches of the film on Pt(111), recently ascribed to the presence of hydroxyls based on XPS measurements 25 . Our observation that a coherent O-Co-O trilayer with a √3 x√3 30° superstructure covers the complete structure might be associated with the "island" nature of the reported trilayers, as opposed to the case of a closed monolayer film.…”

Section: Hydroxyl Overlayersupporting

confidence: 88%

“…A distinct peak at higher BE relative to the upper lattice oxygen component has previously been encountered for O-Fe-O trilayers on Pt(111) 25 as well as in the case of a O-Rh-O trilayer on a Rh(100) surface 26 . Also, including an asymmetry with a tail towards higher binding energy, as observed for the bilayer structure (figure 3b) and also encountered for similar FeO films on Pt(111) 27 , would result in a lower estimate of the OH peak area.…”

Section: Hydroxyl Overlayermentioning

confidence: 53%

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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: 94%

Section: Hydroxyl Overlayersupporting

confidence: 88%

Section: Hydroxyl Overlayermentioning

confidence: 53%

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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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“…265 Indeed, the results indicated that the Pt-oxide interface is more reactive than the fully covered film. [266][267][268][269][270][271] Therefore, until recently, there has been evidence that the open oxide-metal interface (in the spirit of an inverse catalyst: see Section 3.2) is the active site. Very recently, however, experimental evidence that the most active interface under ambient conditions is not the oxide-metal interface but rather the oxide-oxide interface between the FeO double-layer and the FeO 2Àx tri-layer has been provided.…”

Section: Strong Metal Support Interaction (Smsi)mentioning

confidence: 99%

Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems

2018

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Model systems are very important to identify the working principles of real catalysts, and to develop concepts that can be used in the design of new catalytic materials. In this review we report examples of the use of model systems to better understand and control the occurrence of charge transfer at the interface between supported metal nanoparticles and oxide surfaces. In the first part of this article we concentrate on the nature of the support, and on the basic difference in metal/oxide bonding going from a wide-gap non-reducible oxide material to reducible oxide semiconductors. The roles of oxide nanostructuring, bulk and surface defectiveness, and doping with hetero-atoms are also addressed, as they are all aspects that severely affect the metal/oxide interaction. Particular attention is given to the experimental measures of the occurrence of charge transfer at the metal/oxide interface. In this respect, systems based on oxide ultrathin films are particularly important as they allow the use of scanning probe spectroscopies which, often in combination with other measurements and with first principles theoretical simulations, allow full characterization of small supported nanoparticles and their charge state. In a few selected cases, a precise count of the electrons transferred between the oxide and the supported nanoparticle has been possible. Charge transfer can occur through thin, two-dimensional oxide layers also thanks to their structural flexibility. The flow of charge through the oxide film and the formation of charged adsorbates are accompanied in fact by a substantial polaronic relaxation of the film surface which can be rationalized based on electrostatic arguments. In the final part of this review the relationships between model systems and real catalysts are addressed by discussing some examples of how lessons learned from model systems have helped in rationalizing the behavior of real catalysts under working conditions.

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“…A detailed discussion of our APXPS data has been published recently in Ref. [43]; here a brief summary will be given.…”

Section: In Situ Oxidation: Oxidation Of Feo(111) To Feo 2 (111)mentioning

confidence: 99%

A versatile instrument for ambient pressure x-ray photoelectron spectroscopy: The Lund cell approach

2016

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During the past one and a half decades ambient pressure x-ray photoelectron spectroscopy (APXPS) has grown to become a mature technique for the real-time investigation of both solid and liquid surfaces in the presence of a gas or vapour phase. APXPS has been or is being implemented at most major synchrotron radiation facilities and in quite a large number of home laboratories. While most APXPS instruments operate using a standard vacuum chamber as the sample environment, more recently new instruments have been developed which focus on the possibility of custom-designed sample environments with exchangeable ambient pressure cells (AP cells). A particular kind of AP cell solution has been driven by the development of the APXPS instrument for the SPECIES beamline of the MAX IV Laboratory: the solution makes use of a moveable AP cell which for APXPS measurements is docked to the electron energy analyser inside the ultrahigh vacuum instrument. Only the inner volume of the AP cell is filled with gas, while the surrounding vacuum chamber remains under vacuum conditions. The design enables the direct connection of UHV experiments to APXPS experiments, and the swift exchange of AP cells allows different customdesigned sample environments. Moreover, the AP cell design allows the gas-filled inner volume to remain small, which is highly beneficial for experiments in which fast gas exchange is required. Here we report on the design of several AP cells and use a number of cases to exemplify the utility of our approach.

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Oxidation of Ultrathin FeO(111) Grown on Pt(111): Spectroscopic Evidence for Hydroxylation

Cited by 25 publications

References 55 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

Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems

A versatile instrument for ambient pressure x-ray photoelectron spectroscopy: The Lund cell approach

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