In Operando GIXRD and XRR on Polycrystalline In<sub>52</sub>Pd<sub>48</sub>

Ivarsson, Dennis C. A.; Neumann, Matthias; Levin, A. A.; Keilhauer, Toni; Wochner, P.; Armbrüster, Marc

doi:10.1002/zaac.201400223

Cited by 6 publications

(3 citation statements)

References 19 publications

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“…These isotope-labeling experiments prove the active contribution of oxygen from the catalytic material during MSR in the form of a reactive InPd/In 2 O 3 interface. This is strongly supported by operando studies on In-rich bulk InPd, where the formation of an InPd/In 3 Pd 2 /In 2 O 3 surface structure was identified . These results strongly suggest that the intermetallic compound is not the active site, but apparently, an active redox chemistry at the phase boundary of oxide and intermetallic compound is responsible for the high CO 2 selectivity of these catalytic materials and should be observable by the formation of different intermetallic compounds.…”

Section: Resultsmentioning

confidence: 99%

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces

et al. 2020

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Methanol steam reforming provides clean hydrogen by onboard production, which can directly be used for fuel cell applications−while using appropriate catalysts. In x Pd y /In 2 O 3 aerogels exhibit excellent CO 2 selectivities of 99%. This is caused by the active participation of chemically bound oxygen from the material as proven by isotope-labeling experiments. In addition, the dynamic, temperature-dependent equilibrium between intermetallic and oxidic species has a strong impact on the catalytic properties of the material. Thus, the intermetallic compounds in close proximity to a supporting reducible oxide act as selectivity-decisive redox centers, enabling a Mars-van Krevelen mechanism, which is responsible for the excellent selectivity toward CO 2 .

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Section: Resultsmentioning

confidence: 99%

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces

et al. 2020

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“…In a similar temperature regime (723 K) and under reactive atmosphere (presence of methanol and water), experiments on a polycrystalline In-Pd sample have shown that indium segregates to the surface forming In 2 O 3 . 50 The stability of InPd bimetallic particles under oxidation conditions has also been tested and it was shown that the particles fully decompose into Pd and In 2 O 3 already at 573 K. 51 To further understand the trends observed experimentally for the (100) and (111) surfaces, we have performed additional calculations not reported previously. The surface energies of the non-stoichiometric (100) and (111) surfaces have been evaluated by DFT calculations.…”

Section: Discussionmentioning

confidence: 99%

The atomic structure of low-index surfaces of the intermetallic compound InPd

McGuirk

Ledieu

Gaudry

et al. 2015

The Journal of Chemical Physics

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The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ∼580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ∼660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (≥750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and "global" measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature.

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“…[16] The formation of oxide layers on the intermetallic particles was also identified for GaPd 2 [7] and the InÀ Pd system. [13,[24][25][26] Especially for In 2 O 3 -containing materials, the role of partially reduced species or oxygen vacancies was additionally investigated in the hydrogenation of CO 2 to methanol, [27,28] the reverse reaction of MSR. This emphasizes the complex nature of catalytic materials consisting of oxide-supported intermetallic compounds.…”

Section: Introductionmentioning

confidence: 99%

Properties of Bulk In‐Pt Intermetallic Compounds in Methanol Steam Reforming

et al. 2022

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Heterogeneous catalysts are often complex materials containing different compounds. While this can lead to highly beneficial interfaces, it is difficult to identify the role of single components. In methanol steam reforming (MSR), the interplay between intermetallic compounds, supporting oxides and redox reactions leads to highly active and CO 2 -selective materials. Herein, the intrinsic catalytic properties of unsupported In 3 Pt 2 , In 2 Pt, and In 7 Pt 3 as model systems for Pt/In 2 O 3 -based catalytic materials in MSR are addressed. In 2 Pt was identified as the essential compound responsible for the reported excellent CO 2selectivity of 99.5 % at 300 °C in supported systems, showing a CO 2 -selectivity above 99 % even at 400 °C. Additionally, the partial oxidation of In 7 Pt 3 revealed that too much In 2 O 3 is detrimental for the catalytic properties. The study highlights the crucial role of intermetallic InÀ Pt compounds in Pt/In 2 O 3 materials with excellent CO 2 -selectivity.

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In Operando GIXRD and XRR on Polycrystalline In₅₂Pd₄₈

Cited by 6 publications

References 19 publications

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces

The atomic structure of low-index surfaces of the intermetallic compound InPd

Properties of Bulk In‐Pt Intermetallic Compounds in Methanol Steam Reforming

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In Operando GIXRD and XRR on Polycrystalline In52Pd48

Cited by 6 publications

References 19 publications

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective InxPdy/In2O3 Interfaces

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective InxPdy/In2O3 Interfaces

The atomic structure of low-index surfaces of the intermetallic compound InPd

Properties of Bulk In‐Pt Intermetallic Compounds in Methanol Steam Reforming

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In Operando GIXRD and XRR on Polycrystalline In₅₂Pd₄₈

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces

Proving a Paradigm in Methanol Steam Reforming: Catalytically Highly Selective In_xPd_y/In₂O₃ Interfaces