Single Crystal Surfaces

Marsh, Anderson L.; Ribeiro, Fabio H.; Somorjai, Gábor A.

doi:10.1002/9783527610044.hetcat0067

Cited by 13 publications

(4 citation statements)

References 49 publications

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“…This should be seen with respect to the traditional classification or definition of a reaction as structure insensitive based merely on the macroscopically observed catalytic function as typically explored only over a small set of feed conditions. [1][2][3] As exemplified by the data obtained here for RuO 2 (111) and RuO 2 (110) this can be a dangerous concept that does not adequately capture the underlying micro-to mesoscopic complexities. We stress, however, that this is a general statement based on the well-defined theory-theory comparison of the two 1p-kMC models of RuO 2 (110) and RuO 2 (111).…”

Section: Coverage and Turnover Frequency At Catalytically Active Condmentioning

confidence: 85%

“…Detailed kinetic studies comparing the catalytic activity of different single-crystal facets provide important insights on several accounts. They allow for a straightforward assessment of the structure sensitivity of the catalytic reaction [1][2][3] , which constitutes an important first milestone when aiming to relate the detailed knowledge from model catalysts to the performance of real supported catalysts. They also contribute to a more systematic bridging of the materials gap when employed to analyze data obtained for polycrystalline powders.…”

Section: Introductionmentioning

confidence: 99%

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Structure sensitivity in oxide catalysis: First-principles kinetic Monte Carlo simulations for CO oxidation at RuO2(111)

Wang

Reuter

2015

The Journal of Chemical Physics

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We present a density-functional theory based kinetic Monte Carlo study of CO oxidation at the (111) facet of RuO2. We compare the detailed insight into elementary processes, steady-state surface coverages, and catalytic activity to equivalent published simulation data for the frequently studied RuO2(110) facet. Qualitative differences are identified in virtually every aspect ranging from binding energetics over lateral interactions to the interplay of elementary processes at the different active sites. Nevertheless, particularly at technologically relevant elevated temperatures, near-ambient pressures and near-stoichiometric feeds both facets exhibit almost identical catalytic activity. These findings challenge the traditional definition of structure sensitivity based on macroscopically observable turnover frequencies and prompt scrutiny of the applicability of structure sensitivity classifications developed for metals to oxide catalysis.

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Section: Coverage and Turnover Frequency At Catalytically Active Condmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Structure sensitivity in oxide catalysis: First-principles kinetic Monte Carlo simulations for CO oxidation at RuO2(111)

Wang

Reuter

2015

The Journal of Chemical Physics

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“…In this respect, a model catalyst strategy has been developed in which uniform and well-defined surfaces are used as models of powder catalyst surfaces for the studies of surface structure–catalytic property relationships . Single-crystal-based materials have been extensively used as model catalysts, − but there exist the “materials gap” and “pressure gap” between single-crystal-based model catalysts studied under ultrahigh vacuum (UHV) conditions and corresponding powder catalysts working at atmospheric or higher pressures. Consequently, fundamental understandings acquired with single-crystal-based model catalysts sometimes cannot be simply extended to working powder catalysts.…”

Section: Introductionmentioning

confidence: 99%

Oxide Nanocrystal Model Catalysts

2016

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Model catalysts with uniform and well-defined surface structures have been extensively employed to explore structure-property relationships of powder catalysts. Traditional oxide model catalysts are based on oxide single crystals and single crystal thin films, and the surface chemistry and catalysis are studied under ultrahigh-vacuum conditions. However, the acquired fundamental understandings often suffer from the "materials gap" and "pressure gap" when they are extended to the real world of powder catalysts working at atmospheric or higher pressures. Recent advances in colloidal synthesis have realized controlled synthesis of catalytic oxide nanocrystals with uniform and well-defined morphologies. These oxide nanocrystals consist of a novel type of oxide model catalyst whose surface chemistry and catalysis can be studied under the same conditions as working oxide catalysts. In this Account, the emerging concept of oxide nanocrystal model catalysts is demonstrated using our investigations of surface chemistry and catalysis of uniform and well-defined cuprous oxide nanocrystals and ceria nanocrystals. Cu2O cubes enclosed with the {100} crystal planes, Cu2O octahedra enclosed with the {111} crystal planes, and Cu2O rhombic dodecahedra enclosed with the {110} crystal planes exhibit distinct morphology-dependent surface reactivities and catalytic properties that can be well correlated with the surface compositions and structures of exposed crystal planes. Among these types of Cu2O nanocrystals, the octahedra are most reactive and catalytically active due to the presence of coordination-unsaturated (1-fold-coordinated) Cu on the exposed {111} crystal planes. The crystal-plane-controlled surface restructuring and catalytic activity of Cu2O nanocrystals were observed in CO oxidation with excess oxygen. In the propylene oxidation reaction with O2, 1-fold-coordinated Cu on Cu2O(111), 3-fold-coordinated O on Cu2O(110), and 2-fold-coordinated O on Cu2O(100) were identified as the active sites, respectively, to produce acrolein, propylene oxide, and CO2. Ceria rods enclosed with the {110} and {100} crystal planes, ceria cubes enclosed with the {100} crystal planes, and ceria octahedra enclosed with the {111} crystal planes exhibit distinct morphology-dependent oxygen vacancy concentrations and structures that can be well correlated with the surface compositions and structures of exposed crystal planes. Consequently, the metal-ceria interactions, structures, and catalytic performances of ceria-supported catalysts depend on the CeO2 morphology. Our results comprehensively reveal the morphology-dependent surface chemistry and catalysis of oxide nanocrystals that not only greatly deepen the fundamental understanding of oxide catalysis but also demonstrate a morphology-engineering strategy to optimize the catalytic performance of oxide catalysts. These results adequately exemplify the concept of oxide nanocrystal model catalysts for the fundamental investigations of oxide catalysis without the "materials gap" and "pressure gap"....

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“…The traditional model catalysts are single crystal-based model catalysts . Surface-sensitive electron spectroscopic and microscopic characterizations of single crystal-based model catalysts have significantly advanced the fundamental understanding of surface chemistry of solid catalysts. − However, the so-called “materials gap” and “pressure gap” have been well recognized to exist between single crystal-based model catalysts and corresponding powder catalysts due to their differences, respectively, in surface structures and working pressures; thus, the acquired fundamental understanding of single crystal-based model catalysts sometimes cannot be simply extended to corresponding powder catalysts. Meanwhile, due to very small surface areas, reliable evaluations of the catalytic performance of single crystal-based model catalysts are difficult; thus, single crystal-based model catalysts are suitable for fundamental studies of the structure–surface chemistry relation but not of the structure–surface chemistry–activity relation.…”

Section: Introductionmentioning

confidence: 99%

Uniform Catalytic Nanocrystals: From Model Catalysts to Efficient Catalysts

Huang

2023

Acc. Mater. Res.

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Conspectus Solid catalysts play a key role in the chemical industry, energy, and the environment. Fundamental understanding of heterogeneous catalysis exerted by solid surfaces is useful for structural designs of efficient catalysts but is challenging due to the complexity. Emerging uniform catalytic nanocrystals (NCs) with controlled and well-defined surface structures have brought new opportunities for fundamental understanding and directed explorations of efficient catalysts. In a previous Account (Acc. Chem. Res.201649520527), I postulated and exemplified a concept of oxide nanocrystal model catalysts for the fundamental investigations of oxide catalysis without the “materials gap” and “pressure gap” which are often encountered using the traditional single crystal model catalysts. In this Account, I summarize our effort in fabricating efficient uniform nanocrystal catalysts based on the fundamental understanding of structure–activity relations and reaction mechanisms acquired by oxide nanocrystal model catalyst studies. Directed by the fundamental understanding that the Cu2O{110} facet is active in catalyzing propylene epoxidation with O2 and the fine Cu2O nanocube exposes high densities of Cu2O{110} edge sites, we successfully explore fine Cu2O nanocubes as a highly selective catalyst for propylene epoxidation with O2. Directed by the fundamental understanding that the Cu{100} facet is the active Cu facet in catalyzing the water–gas shift (WGS) reaction, we successfully fabricate a highly active ZnO/fine Cu nanocube WGS catalyst with enhanced ZnO-CuCu{100} active site density. Directed by the fundamental understanding of TiO2 facet effects on the surface band bending and adsorbate–surface interfacial energy level alignment, and consequent photocatalytic performance, we successfully fabricate highly active TiO2{001} NC-based photocatalysts for photocatalytic CH4 conversions. These results adequately exemplify the concept of fundamental understanding-directed explorations of efficient catalysts following a strategy of “identification of active site structure + maximization of active site density”, which, together with the advancement of controlled-synthesis methods, is expected to greatly accelerate the explorations of novel and efficient catalysts in future.

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Single Crystal Surfaces

Abstract: The sections in this article are Introduction Techniques Examples of Studies with Single Crystals The Active Site Model of a Catalytic Surface Catalysis over an Adsorbed Overlayer Structure‐Sensitive or Structure‐Insensitive Reactions … Show more

Cited by 13 publications

References 49 publications

Structure sensitivity in oxide catalysis: First-principles kinetic Monte Carlo simulations for CO oxidation at RuO2(111)

Structure sensitivity in oxide catalysis: First-principles kinetic Monte Carlo simulations for CO oxidation at RuO2(111)

Oxide Nanocrystal Model Catalysts

Uniform Catalytic Nanocrystals: From Model Catalysts to Efficient Catalysts

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