Growth and Atomic‐Scale Characterization of Ultrathin Silica and Germania Films: The Crucial Role of the Metal Support

Lewandowski, Adrian; Tosoni, Sergio; Gura, Leonard; Yang, Zechao; Fuhrich, Alexander; Prieto, Maurício J.; Schmidt, Thomas; Usvyat, Denis; Schneider, W. D.; Heyde, Markus; Pacchioni, Gianfranco; Freund, Hans‐Joachim

doi:10.1002/chem.202001806

Cited by 15 publications

(31 citation statements)

References 130 publications

(392 reference statements)

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Section: Conclusion and Perspectivessupporting

confidence: 66%

“…Another perspective comes into play, namely, the possible preparation of another group of the IV oxide films, such as germania, which may expose similar structures and transformations, but at lower crystallization temperatures. Indeed, initial studies on germania films have been performed, and structural determinations have been started. ,, Figure shows a comparison of a silica film and a corresponding germania film with structural schemes. Both can exist as vitreous films.…”

Section: Conclusion and Perspectivessupporting

confidence: 56%

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Two-Dimensional Ultrathin Silica Films

Zhong

Freund

2022

Chem. Rev.

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Two-dimensional (2D) ultrathin silica films have the potential to reach technological importance in electronics and catalysis. Several well-defined 2D-silica structures have been synthesized so far. The silica bilayer represents a 2D material with SiO2 stoichiometry. It consists of precisely two layers of tetrahedral [SiO4] building blocks, corner connected via oxygen bridges, thus forming a self-saturated silicon dioxide sheet with a thickness of ∼0.5 nm. Inspired by recent successful preparations and characterizations of these 2D-silica model systems, scientists now can forge novel concepts for realistic systems, particularly by atomic-scale studies with the most powerful and advanced surface science techniques and density functional theory calculations. This Review provides a solid introduction to these recent developments, breakthroughs, and implications on ultrathin 2D-silica films, including their atomic/electronic structures, chemical modifications, atom/molecule adsorptions, and catalytic reactivity properties, which can help to stimulate further investigations and understandings of these fundamentally important 2D materials.

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Section: Conclusion and Perspectivessupporting

confidence: 66%

Section: Conclusion and Perspectivessupporting

confidence: 56%

Two-Dimensional Ultrathin Silica Films

Zhong

Freund

2022

Chem. Rev.

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“…DBs have been reported in supported honeycomb monolayers of SiO 2 on Ru(0001) and Mo(112), germania (GeO 2 ) on Ru(0001), Ti 2 O 3 on Pt(111), V 2 O 3 on Pd(111), and silicene on Ag(111). [10][11][12][13][14][15][16][17] Monolayer SiO 2 and GeO 2 consist of tetrahedral-shaped [SiO 4 ] or [GeO 4 ] structural units arranged in a planar honeycomb lattice. Ti 2 O 3 and V 2 O 3 monolayers form a hexagonal network in which each hexagonal ring contains six metal atoms and six oxygen atoms.…”

mentioning

confidence: 99%

Epitaxially Constrained Grain Boundary Structures in an Oxide Honeycomb Monolayer

Wang

Goniakowski

et al. 2022

Adv Materials Inter

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Grain boundaries (GBs) are ubiquitous in solids. Their description is critical for understanding polycrystalline materials and explaining their mechanical and electrical properties. A GB in a 2D material can be described as a line defect and its atomic structures have been intensively studied in materials such as graphene. These GBs accommodate the relative rotation of two neighboring grains by incorporating periodic units consisting of nonhexagonal rings along the boundary. Zero‐degree GBs, called domain boundaries (DBs), where there is only a lattice offset between two grains without any rotation, are rare in 2D van‐der‐Waals (vdW) bonded materials where the grains can easily move. However, this movement is not possible in 2D materials that have a strong epitaxial relationship with their substrate such as the M2O3 (2 × 2) honeycomb monolayers on noble metal (111) supports. Involving experimental and theoretical investigations, four main DBs are observed here in a monolayer of Ti2O3 supported on Au(111) and their atomic structures are solved. The DB formation energies explain why some DBs are more frequently observed than others. The strong epitaxial constraint from the Au(111) substrate stabilizes some unique Ti2O3 monolayer DB structures that are not observed in vdW‐bonded 2D materials.

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“…However, in both cases, the thin films that have been prepared do not appear to be representative of the respective bulk oxides when it comes to adatom adsorption. For SiO 2 , quasi-2D monolayer and bilayer films have been grown on a variety of metal substrates. , Pd adatoms deposited on bilayer SiO 2 /Ru(0001) at room temperature were shown to diffuse through nanopores in the film to the metal support even in the crystalline phase in the absence of defects. Au adatoms were slightly more stable but similarly diffused through the film at defects .…”

Section: Perspectivementioning

confidence: 99%

Single-Atom Catalysis: Insights from Model Systems

Kraushofer

Parkinson

2022

Chem. Rev.

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The field of single atom catalysis (SAC) has expanded greatly in recent years. While there has been much success developing new synthesis methods, a fundamental disconnect exists between most experiments and the theoretical computations used to model them. The real catalysts are based on powder supports, which inevitably contain a multitude of different facets, different surface sites, defects, hydroxyl groups, and other contaminants due to the environment. This makes it extremely difficult to determine the structure of the active SAC site using current techniques. To be tractable, computations aimed at modelling SAC utilize periodic boundary conditions and low index facets of an idealized support. Thus the reaction barriers and mechanisms determined computationally represent, at best, a plausibility argument, and there is a strong chance that some critical aspect is omitted. One way to better understand what is plausible is by experimental modelling, i.e. comparing the results of computations to experiments based on precisely defined single-crystalline supports prepared in an ultrahigh vacuum (UHV) environment. In this article, we review the status of the surface science literature as it pertains to SAC. We focus on experimental work on supports where the site of the metal atom are unambiguously determined from experiment, in particular the surfaces of rutile and anatase TiO2, the iron oxides Fe2O3 and Fe3O4, as well as CeO2 and MgO. Much of this work is based on scanning probe microscopy in conjunction with spectroscopy, and we highlight the remarkably few studies in which metal atoms are stable on low index surfaces of typical supports. In a perspective, we discuss the possibility for expanding such studies into other relevant supports such as N-doped carbon, graphene and metal carbides.

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Growth and Atomic‐Scale Characterization of Ultrathin Silica and Germania Films: The Crucial Role of the Metal Support

Cited by 15 publications

References 130 publications

Two-Dimensional Ultrathin Silica Films

Two-Dimensional Ultrathin Silica Films

Epitaxially Constrained Grain Boundary Structures in an Oxide Honeycomb Monolayer

Single-Atom Catalysis: Insights from Model Systems

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