The interaction of COO<sub>2</sub> gas mixtures with Au tips: <i>in situ</i> imaging and local chemical probing

Bocarmé, Thierry Visart de; Chau, Thoi-Dai; Kruse, Norbert

doi:10.1002/sia.2483

Cited by 7 publications

(5 citation statements)

References 27 publications

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“…Small nanoclusters may also be able to activate O 2 . − Field-ion microscopy experiments have shown that a Au tip can change in response to an O 2 atmosphere, and it was proposed that a surface oxide was formed . However, several later studies show negligible O 2 dissociation or catalytic activity for nanostructured Au, even for Au nanoparticles on non-oxide supports. ,− Recently, experimental and computational work have suggested that twinning sites on nanostructured Au may be able to catalyze CO oxidation by O 2…”

Section: Mechanisms and Barriers For O2 Dissociationmentioning

confidence: 99%

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

et al. 2017

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The activation of O on metal surfaces is a critical process for heterogeneous catalysis and materials oxidation. Fundamental studies of well-defined metal surfaces using a variety of techniques have given crucial insight into the mechanisms, energetics, and dynamics of O adsorption and dissociation. Here, trends in the activation of O on transition metal surfaces are discussed, and various O adsorption states are described in terms of both electronic structure and geometry. The mechanism and dynamics of O dissociation are also reviewed, including the importance of the spin transition. The reactivity of O and O toward reactant molecules is also briefly discussed in the context of catalysis. The reactivity of a surface toward O generally correlates with the adsorption strength of O, the tendency to oxidize, and the heat of formation of the oxide. Periodic trends can be rationalized in terms of attractive and repulsive interactions with the d-band, such that inert metals tend to feature a full d band that is low energy and has a large spatial overlap with adsorbate states. More open surfaces or undercoordinated defect sites can be much more reactive than close-packed surfaces. Reactions between O and other species tend to be more prevalent than reactions between O and other species, particularly on more reactive surfaces.

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Section: Mechanisms and Barriers For O2 Dissociationmentioning

confidence: 99%

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

et al. 2017

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“…One of the advantages of this technique is to allow the study of catalytic reactions in the absence of any influence of the oxidic support, which is of great importance for the fundamental understanding of the catalytic system. In addition to this, the behaviours observed are influenced by the presence of a steady electric field which could mimic conditions encountered in studies over Au δ+ /metal-oxide catalysts [196]. In Figure 13a, we can observe a typical Au sample prepared and imaged by field ion microscopy.…”

Section: Processes On Au Tips Propagation Waves During Co/o 2 Interacmentioning

confidence: 79%

Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

et al. 2017

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Abstract:Since the early discovery of the catalytic activity of gold at low temperature, there has been a growing interest in Au and Au-based catalysis for a new class of applications. The complexity of the catalysts currently used ranges from single crystal to 3D structured materials. To improve the efficiency of such catalysts, a better understanding of the catalytic process is required, from both the kinetic and material viewpoints. The understanding of such processes can be achieved using environmental imaging techniques allowing the observation of catalytic processes under reaction conditions, so as to study the systems in conditions as close as possible to industrial conditions. This review focuses on the description of catalytic processes occurring on Au-based catalysts with selected in situ imaging techniques, i.e., PEEM/LEEM, FIM/FEM and E-TEM, allowing a wide range of pressure and material complexity to be covered. These techniques, among others, are applied to unravel the presence of spatiotemporal behaviours, study mass transport and phase separation, determine activation energies of elementary steps, observe the morphological changes of supported nanoparticles, and finally correlate the surface composition with the catalytic reactivity.

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“…Nonetheless, it has been shown that the catalytic contribution of silver is crucial [35,36]. As compared to pure Au [37][38][39], Ag has much stronger interactions with oxygen [40,41] and can therefore be considered as the atomic oxygen provider in Au-Ag based catalysis for oxidation reactions.…”

Section: Au-88%at Ag Exposure To Nomentioning

confidence: 99%

Surface Reconstruction of Ag and Au–Ag Model Nano-catalysts During Exposure to Oxidising Gas Atmospheres

2020

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At the industrial level, Ag catalysts in the form of silver crystals held by a silver gauze are largely used for formaldehyde production and ethylene epoxidation. These self-supported structures undergo surface reconstructions and morphological changes upon exposure to moderately high temperatures (473-900 K) and oxidising atmospheres. These phenomena have been studied and well understood on single crystal surfaces and polycrystalline foils: different oxygen surface and sub-surface species have been identified and reconstruction processes explained. To verify the scalability of the surface science results and ultimately understand these phenomena on catalysts at the industrial scale, further studies on more complex samples are needed. Attempts to close this "materials gap" have been carried out in this present study where experiments have been performed on model single catalytic nanoparticles, i.e. the apexes of field emitter tips, using both field emission (FE) and field ion (FI) microscopies. Pure Ag samples are exposed to a pressure of 3 × 10-5 mbar of O 2 at temperatures up to 700 K. These conditions reflect those used on the industrial scale. Important surface/morphological reconstructions are observed both in FE and FI modes. For comparison, experiments have been repeated on Au-8.8%at. Ag field emitter tips, representative samples for Au-Ag catalytic nanofoams, using to 3 × 10-5 mbar of NO 2 at temperatures up to 450 K. Similar behaviour are observed and the influence of the oxidising gas is discussed.

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The interaction of COO₂ gas mixtures with Au tips: in situ imaging and local chemical probing

Cited by 7 publications

References 27 publications

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

Surface Reconstruction of Ag and Au–Ag Model Nano-catalysts During Exposure to Oxidising Gas Atmospheres

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The interaction of COO2 gas mixtures with Au tips: in situ imaging and local chemical probing

Cited by 7 publications

References 27 publications

O2Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

O2Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

Surface Reconstruction of Ag and Au–Ag Model Nano-catalysts During Exposure to Oxidising Gas Atmospheres

Contact Info

Product

Resources

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The interaction of COO₂ gas mixtures with Au tips: in situ imaging and local chemical probing

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts

O₂Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts