Strong Interactions in Supported-Metal Catalysts

Tauster, S.J.; Fung, S.C.; Baker, Rose M.; Horsley, J. A.

doi:10.1126/science.211.4487.1121

Cited by 1,218 publications

(839 citation statements)

References 13 publications

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“…In addition, the Mössbauer measurements reveal the presence of high spin Fe 2+ species with quadrupole splittings at room temperature (2.7-1.7 mm/s) significantly higher than for bulk FeO (about 0.55 mm/s). These results point to the formation of ferrous species due to an intimate interaction with the support [9][10][11][13][14][15]18,[20][21][22][23][24]. One of the two iron(II) species is identified as a Fe 2+ which upon formation immediately migrates into the zirconia support to form a mixed oxide.…”

Section: Reduction and Reduction Model Of Fe/zromentioning

confidence: 99%

“…The aim of the present study is to elucidate the reduction behaviour (the activation process) of the unpromoted (Fe/ZrO 2 ) and the potassium-promoted (Fe/K/ZrO 2 ) zirconia-supported iron catalysts at ambient hydrogen pressure in more details than already reported in the literature [9][10][11][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…Wielers et al [21] observed the formation of a silicate layer during reduction of trivalent iron indicating that, as soon as divalent iron is formed, iron migrates into the support. Also with TiO 2 and MgO supports mixed oxides are mentioned to account for the intimate contact between the precursor metal oxide and the support resulting in a lower reducibility of the iron oxide [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

Berg

Crajé

Kraan

et al. 2003

Applied Catalysis A: General

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The reduction behaviour (the activation process) of two iron-based Fischer-Tropsch catalysts viz. an unpromoted and a potassium-promoted zirconia-supported iron catalyst is investigated. The initial dispersion of both catalysts is very high. To establish the nature of the iron species under hydrogen atmosphere, experiments were performed at ambient pressure. It is demonstrated for both catalysts that during reduction the carbon originating from the citrate complex used in the preparation procedure is not completely removed, whereby the largest amount of the carbon species is encountered on the potassium-promoted catalyst. During reduction at ambient pressure this residual carbon reacts with metallic iron and forms cementite (θ-Fe 3 C). The iron oxide of the potassium-promoted catalyst turns out to reduce more easily than the oxide of the unpromoted catalyst. Upon formation of divalent iron, this divalent species readily reacts with the support to give a stable mixed oxide. This mixed oxide is suggested to be a prerequisite in maintaining a high dispersion of the metallic iron particles. Based on the analyses presented here, a reduction model is proposed.

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Section: Reduction and Reduction Model Of Fe/zromentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

Berg

Crajé

Kraan

et al. 2003

Applied Catalysis A: General

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“…The uptake of hydrogen on Pt/TiO 2 could be restored by reoxidation followed by low-temperature reduction. This phenomenon, including electronic and geometric effects [8][9][10][11][12][13][14][15][16][17], has been extensively investigated. Nevertheless, many researchers failed to distinguish the electronic effects from the geometric effects, labeling them together as 'strong metal-support interaction' (SMSI).…”

Section: Introductionmentioning

confidence: 99%

Naphthalene hydrogenation over Pt/TiO2–ZrO2 and the behavior of strong metal–support interaction (SMSI)

Lu¹,

Lin²,

Wang³

2000

Applied Catalysis A: General

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Vapor-phase naphthalene hydrogenation over various supported Pt catalysts was studied in a continuous fixed-bed microreactor. Experimental results indicated that the catalytic activity of the catalyst strongly depended on the nature of the support and the pre-reduction temperature. Reaction order was independent of the support as the reaction was pseudo-first-order with respect to naphthalene in the temperature range studied. By comparing the apparent rate constant over various supported Pt catalysts, Pt supported on TiO 2 -ZrO 2 (1 : 1) reduced at a low temperature showed the highest activity. For higher pre-reduction temperatures, Pt/TiO 2 -ZrO 2 (1 : 1) exhibited the least suppression of H 2 uptake, due to a stabilization effect exerted by ZrO 2 , which prevents the migration of TiO x moieties and the blockage of the Pt surface. However, the apparent depression of the hydrogenation activity of high-temperature reduced Pt/TiO 2 -ZrO 2 (1 : 1) was significantly greater than the suppression of its hydrogen uptake. Furthermore, the decreasing value of the hydrogenation activity relative to the hydrogen uptake demonstrates electron perturbations between the support and the Pt metal.

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“…The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions [2][3][4] . Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" Fe3O4 substrates by in-situ microscopy ( Figure 1).…”

mentioning

confidence: 99%

Dynamic Investigation of Metal-support Interactions in Heterodimer Nanoparticles by in situ Transmission Electron Microscopy

et al. 2017

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Catalysts are critical components of many current technologies and essential components of sustainable energy systems ranging from fuel cells and batteries to turning biomass into useful chemicals or fuels by enabling reactions to be guided quickly and efficiently along desirable pathways rather than those that are inefficient or lead to unwanted byproducts. Fundamental investigations of catalyst structures and the mechanisms of catalytic reactions requires characterization imaging of surfaces at the atomic scale and probing the structures and energetics of the reacting molecules as they function under reaction condition on varying time and length scales. High-angle annular dark field (HAADF) STEM is an indispensable technique for analyzing heterogeneous catalysts, in particular those comprising high atomic number (Z) metallic nanoparticles (NPs) dispersed on low-Z supports 1 . Readily interpretable atomic-scale Z-contrast imaging with high spatial resolution spectroscopy, including X-ray energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS), allows researchers to investigate structural information such as dimensions, morphologies, and size distribution of catalytic NPs as well as their material chemistry (e.g., chemical composition, bonding of catalytic particles with supports at interface, etc.).The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions 2-4 . Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" Fe3O4 substrates by in-situ microscopy ( Figure 1). The in situ heating experiments performed (up to 500 C) under reducing conditions using aberration-corrected TEM and Protochips Co. Aduro TM MEMS-based heating technology resulted in very interesting wetting behavior (Figure 2). In some of the heterodimer structures, we also observed epitaxial wetting behavior suggesting that there are special crystal facets allowing epitaxial wetting between Au and Fe3O4. This epitaxial wetting mechanism also relatively slower than the one with no epitaxial relationship between the oxide and support. During in-situ vacuum annealing of Au-Fe3O4 dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe3O4 on Au nanoparticles, the gold nanoparticles transform into monolayered gold films and wet the surface of nano-Fe3O4, as the surface reduction of nano-Fe3O4 proceeds. Moreover, DFT calculations show progressively stronger binding of Au films with the reduction of the iron oxide support. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe3O4 and the extremely strong adhesion between Au and the reduced Fe3O4.In summary, we have employed a combination of in-situ TEM, XPS, and DFT calculations to obtain a mechanistic understanding of the wetting behavior of the gold nanoparticles in dumbbell-like nanop...

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Strong Interactions in Supported-Metal Catalysts

Cited by 1,218 publications

References 13 publications

Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

Naphthalene hydrogenation over Pt/TiO2–ZrO2 and the behavior of strong metal–support interaction (SMSI)

Dynamic Investigation of Metal-support Interactions in Heterodimer Nanoparticles by in situ Transmission Electron Microscopy

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