Structure determination of Ni(111)c(4 × 2)-CO and its implications for the interpretation of vibrational spectroscopic data

Dávila, M. E.; Asensio, M. C.; Woodruff, D.P.; Schindler, K.‐M.; Hofmann, Philip; Weiß, K.; Dippel, R.; Gardner, Peter; Fritzsche, V.; Bradshaw, Alexander M.; Conesa, J.C.; González‐Elipe, Agustín R.

doi:10.1016/0039-6028(94)91424-9

Cited by 105 publications

(27 citation statements)

References 47 publications

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“…Previous infrared line shape studies of this system had estimated the energy of the NO frustrated translation to be about 7.5 meV from the temperature dependence of the vibrational line shape of the NO internal stretch, 11 where line broadening of the high energy mode was attributed to anharmonic coupling to the lower energy frustrated translation. We also note that the energy of this feature is similar to that calculated using cluster calculations for the frustrated translation of another diatomic molecule, CO, 17 as well as to a feature assigned to frustrated translations of CO adsorbed in threefold sites in the c͑4ϫ2͒ structure on Ni͑111͒ 18 ͓CO on Ni͑111͒ is now known to adsorb in threefold hollow sites 19 ͔. This feature is absent on the clean surface, and the energy of this feature at the substrate Brillouin zone edge is well below that of the Rayleigh wave and bulk phonon bands of Ni͑111͒, thus precluding its assignment as a substrate mode.…”

Section: Methodssupporting

confidence: 71%

Interadsorbate interactions in the c(4×2) NO/Ni(111) system

Stirniman

Sibener

1995

The Journal of Chemical Physics

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Electron energy loss spectroscopy has been used to map the dispersion of the dipole active internal NO stretch and of the NO frustrated translation, which has not been previously observed, in the c͑4ϫ2͒ NO/Ni͑111͒ system. The dispersion of the dipole active mode was fit with a model that assumed electrostatic dipole-dipole coupling ͑including image dipoles͒ between the adsorbates. The frustrated translation, on the other hand, showed no dispersion to within the resolution of the experiment across the entire surface Brillouin zone of the Ni͑111͒ substrate. These measurements reveal new information on interadsorbate interactions in an important model system.

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Section: Methodssupporting

confidence: 71%

Interadsorbate interactions in the c(4×2) NO/Ni(111) system

Stirniman

Sibener

1995

The Journal of Chemical Physics

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“…This procedure has been based on the extensive structural and vibrational data on coordination compounds which show how this mode softens as the CO-metal coordination increases. More recently, true structural studies of a number of such molecular adsorption systems have highlighted the dangers of extending the interpretation of such vibrational frequencies too far (Asensio et al, 1992;Davila et al, 1994). Nevertheless, it is clear that spectral fingerprinting has real advantages in characterizing the phenomenology of adsorption systems, and the information on the number of distinct states is a valuable source of input to any proper structural study (as, indeed, in the alkali/aluminium case described above).…”

Section: Sxpsmentioning

confidence: 99%

Photoemission Studies of Adsorbates on Metal Surfaces

Woodruff¹

1995

J Synchrotron Radiat

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A brief review is presented of the general field of synchrotron radiation photoemission of adsorbates on well characterized metal surfaces, contrasting some of the earliest work of the 1970s with more recent experiments, and highlighting some of the likely future developments that may derive from the use of third-generation synchrotron radiation facilities. Four general types of study are identified: shallow core-level photoemission either for the fingerprinting of the chemical state, or for quantitative structural studies via photoelectron diffraction, and valence-level photoemission either to study the two-dimensional band structure of adsorbate-induced surface-localized states, or to investigate the orientation of molecular adsorbates through the use of symmetry selection rules.

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“…With increasing CO pressure, the Zr 4+ –CO peak grows and obscures the Ni 2+ –CO peak. The band at 2060 cm −1 appearing at 0.1 mbar pressure is attributed to linearly adsorbed CO on Ni 0 and the broad band(s) below 2000 cm −1 are attributed to threefold hollow bonded CO on Ni 0 [69–71]. The band at 2120 cm −1 , shifting to 2127 cm −1 with increasing CO pressure, is attributed to Ni + –CO.…”

Section: Resultsmentioning

confidence: 99%

Surface Spectroscopy on UHV-Grown and Technological Ni–ZrO2 Reforming Catalysts: From UHV to Operando Conditions

Anic

Wolfbeisser

et al. 2016

Top Catal

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Ni nanoparticles supported on ZrO2 are a prototypical system for reforming catalysis converting methane to synthesis gas. Herein, we examine this catalyst on a fundamental level using a 2-fold approach employing industrial-grade catalysts as well as surface science based model catalysts. In both cases we examine the atomic (HRTEM/XRD/LEED) and electronic (XPS) structure, as well as the adsorption properties (FTIR/PM-IRAS), with emphasis on in situ/operando studies under atmospheric pressure conditions. For technological Ni–ZrO2 the rather large Ni nanoparticles (about 20 nm diameter) were evenly distributed over the monoclinic zirconia support. In situ FTIR spectroscopy and ex situ XRD revealed that even upon H2 exposure at 673 K no full reduction of the nickel surface was achieved. CO adsorbed reversibly on metallic and oxidic Ni sites but no CO dissociation was observed at room temperature, most likely because the Ni particle edges/steps comprised Ni oxide. CO desorption temperatures were in line with single crystal data, due to the large size of the nanoparticles. During methane dry reforming at 873 K carbon species were deposited on the Ni surface within the first 3 h but the CH4 and CO2 conversion hardly changed even during 24 h. Post reaction TEM and TPO suggest the formation of graphitic and whisker-type carbon that do not significantly block the Ni surface but rather physically block the tube reactor. Reverse water gas shift decreased the H2/CO ratio. Operando studies of methane steam reforming, simultaneously recording FTIR and MS data, detected activated CH4 (CH3 and CH2), activated water (OH), as well as different bidentate (bi)carbonate species, with the latter being involved in the water gas shift side reaction. Surface science Ni–ZrO2 model catalysts were prepared by first growing an ultrathin “trilayer” (O–Zr–O) ZrO2 support on an Pd3Zr alloy substrate, and subsequently depositing Ni, with the process being monitored by XPS and LEED. Apart from the trilayer oxide, there is a small fraction of ZrO2 clusters with more bulk-like properties. When CO was adsorbed on the (fully metallic) Ni particles at pressures up to 100 mbar, both PM-IRAS and XPS indicated CO dissociation around room temperature and blocking of the Ni surface by carbon (note that on the partially oxidized technological Ni particles, CO dissociation was absent). The Ni nanoparticles were stable up to 550 K but annealing to higher temperatures induced Ni migration through the ultrathin ZrO2 support into the Pd3Zr alloy. Both approaches have their benefits and limitations but enable us to address specific questions on a molecular level.

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Structure determination of Ni(111)c(4 × 2)-CO and its implications for the interpretation of vibrational spectroscopic data

Cited by 105 publications

References 47 publications

Interadsorbate interactions in the c(4×2) NO/Ni(111) system

Interadsorbate interactions in the c(4×2) NO/Ni(111) system

Photoemission Studies of Adsorbates on Metal Surfaces

Surface Spectroscopy on UHV-Grown and Technological Ni–ZrO2 Reforming Catalysts: From UHV to Operando Conditions

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