Structural analysis of the intermetallic surface compound<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">CePt</mml:mi><mml:mn>5</mml:mn></mml:msub><mml:mo>/</mml:mo><mml:mi mathvariant="normal">Pt</mml:mi><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:math>

Kemmer, Jeannette; Praetorius, Christian; Krönlein, Andreas; Hsu, Pin-Jui; Fauth, K.; Bode, Matthias

doi:10.1103/physrevb.90.195401

Cited by 11 publications

(22 citation statements)

References 28 publications

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“…On the contrary, on the areas comprising mainly the phase with a reflectivity lower than Pt μLEED shows superstructures with a 5/2(√3 × √3)R30° periodicity (Figure 4 L2). In the literature a similar superstructure was observed by LEED at the early stages of Pt-Ce alloy formation and ascribed to a metallic Pt 5 Ce alloy (Baddeley et al, 1997; Kemmer et al, 2014). This suggests that there might be a non-negligible tendency for interatomic exchange between cerium oxide and Pt induced by the thermal reduction.…”

Section: Resultssupporting

confidence: 67%

“…The thickness of metallic cerium is also expressed in MLE, where 1 MLE CeO 2 ~1 MLE Ce since the atomic densities of cerium in its metal structure and in the oxide are almost the same. Reduction by cerium deposition in UHV was applied only to closed cerium oxide films, to avoid direct interactions between Ce and Pt, which are known to give origin to ordered alloyed phases (Baddeley et al, 1997; Berner and Schierbaum, 2002; Kemmer et al, 2014). The re-oxidation is performed by thermal treatments at 1,040 K in O 2 background pressure of 1 × 10 −7 Torr.…”

Section: Methodsmentioning

confidence: 99%

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Dynamics of the Interaction Between Ceria and Platinum During Redox Processes

et al. 2019

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The work is focused on understanding the dynamics of the processes which occur at the interface between ceria and platinum during redox processes, by investigating an inverse catalytic model system made of ceria epitaxial islands and ultrathin films supported on Pt(111). The evolution of the morphology, structure and electronic properties is analyzed in real-time during reduction and oxidation, using low-energy electron microscopy and spatially resolved low-energy electron diffraction. The reduction is induced using different methods, namely thermal treatments in ultra-high vacuum and in H2 as well as deposition of Ce on the oxide surface, while re-oxidation is obtained by exposure to oxygen at elevated temperature. The use of two different epitaxial systems, continuous films and nanostructures, allows determining the influence of platinum proximity on the stabilization of the specific phases observed. The factors that limit the reversibility of the observed modifications with the different oxidation treatments are also discussed. The obtained results highlight important aspects of the cerium oxide/Pt interaction that are relevant for a complete understanding of the behavior of Pt/CeO2 catalysts.

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Section: Resultssupporting

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Dynamics of the Interaction Between Ceria and Platinum During Redox Processes

et al. 2019

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“…The formation of the same alloy was observed for metallic Ce layers deposited on the Pt(111) surface and annealed in vacuum at intermediate temperatures in previous papers. [ 35,36,43 ] Evidences of mass exchange processes between cerium oxide films and the Pt substrate under reducing conditions have also been observed by scanning microscopies [ 37 ] and low energy electron microscopy [ 20 ] and they are fully consistent with the results of the EXAFS analysis illustrated in Section 2.1.…”

Section: Resultssupporting

confidence: 69%

Structure of Reduced Cerium Oxide Ultrathin Films on Pt(111): Local Atomic Environment and Long‐Range Order

Cresi

Carlà

Znaiguia

et al. 2020

Adv Materials Inter

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To optimize the catalytic functionality of cerium oxide it is important to understand the structural modifications associated with reduction and the role of the proximity of metals, which are often coupled with the oxide in the applications. For this purpose, the evolution of the short‐ and long‐range structure of cerium oxide ultrathin epitaxial films and nanostructures supported on Pt(111) is investigated using X‐ray absorption spectroscopy at the Ce L3 edge and surface X‐ray diffraction, during reduction by thermal treatments in vacuum. In epitaxial nanoislands reduction is associated with a contraction of the Ce–O distance and with the appearance of CePt bonds. The formation of a phase with a (2 × 2) periodicity after a thermal treatment at 1023 K is ascribed to the formation of a Pt5Ce alloy. Films of 3 nm thickness do not show, on average, significant structural modifications with the same thermal treatment, consistent with the hypothesis that the reduction involves only the topmost surface layers and it does not influence significantly the bulk structure of the material. This study demonstrates a strong interaction between cerium oxide and platinum, which has implications for the reactivity and stability of catalysts based on metals combined with reducible oxides.

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“…They are readily identified by their characteristic LEED patterns [7]. For the La-Pt system we observe a similar succession of structural phases as in CePt 5 [9,25] which, however, evolves much faster as a function of coverage. Nevertheless, from the reported evidence and similarities between the phases [26,27], Auger electron spectroscopy, and the results below we conclude that the La-Pt phases consist of LaPt 5 .…”

mentioning

confidence: 52%

Study of crystal-field splitting in ultrathinCePt5films by Raman spectroscopy

et al. 2017

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Low-temperature electronic properties of rare-earth intermetallics are substantially influenced by the symmetry and magnitude of the crystal electric field. The direct spectroscopic analysis of crystal field splitting can be challenging, especially in low-dimensional systems, because it requires both high spectral resolution and pronounced sensitivity. We demonstrate the eligibility of electronic Raman spectroscopy for this purpose by the direct determination of the 4f level splitting in ultrathin ordered CePt5 films down to 1.7 nm thickness on Pt(111). Crystal field excitations of Ce 4f electrons give rise to Raman peaks with energy shifts up to ≈ 25 meV. Three distinct peaks occur which we attribute to inequivalent Ce sites, located (i) at the interface to the substrate, (ii) next to the Pt-terminated surface, and (iii) in the CePt5 layers in between. The well-resolved Raman signatures allow us to identify a reduced crystal field splitting at the interface and an enhancement at the surface, highlighting its strong dependence on the local atomic environment.

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Structural analysis of the intermetallic surface compoundCePt5/Pt(111)

Cited by 11 publications

References 28 publications

Dynamics of the Interaction Between Ceria and Platinum During Redox Processes

Dynamics of the Interaction Between Ceria and Platinum During Redox Processes

Structure of Reduced Cerium Oxide Ultrathin Films on Pt(111): Local Atomic Environment and Long‐Range Order

Study of crystal-field splitting in ultrathinCePt5films by Raman spectroscopy

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