Some contributions of electron microscopy to the characterisation of the strong metal–support interaction effect

Bernal, S.; Calvino, José J.; Cauqui, M.A.; Gatica, José M.; López-Cartés, C.; Pérez-Omil, Jose A.; Pintado, José

doi:10.1016/s0920-5861(02)00382-6

Cited by 186 publications

(169 citation statements)

References 57 publications

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“…It is likely that these features constitute a drawback also for transmission electron microscopy (TEM) analysis, although 3 nm Pt particles on CeO 2 were actually detected by TEM. 7 An estimate of the mean particle size based on the number of first neighbors as determined by EXAFS 36 gave an average size of about 1.5-1.8 nm, corresponding to about eight first neighbors (Table 1). It is worth noticing that this evaluation is in quite good agreement with small-angle X-ray scattering results.…”

Section: Discussionmentioning

confidence: 99%

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Deganello¹,

Giannici²,

Martorana³

et al. 2006

J. Phys. Chem. B

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The catalyst Pt(1 wt %)/Ce 0.6 Zr 0.4 O 2 is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L III edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce 0.6 Zr 0.4 O 2 is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formation of a platinum-cerium alloy in redox-aged samples and the stability of the metal particles toward oxidation and sintering during high-temperature treatments. Under CO flux at 773 K, bare ceria-zirconia shows a continuous drift of diffraction peaks toward smaller Bragg angles, due to a progressive increase of Ce(III) content. Under the same treatment, the structural rearrangement of Pt-supported ceria-zirconia starts after an induction time and takes place with an abrupt change of the lattice constant. The experimental evidence points to the role of supported Pt in modifying the redox properties of ceria-zirconia with respect to the bare support. It is proposed that the much faster bulk reduction observed by in situ XRD for redox-aged Pt/ceria-zirconia can be attributed to an easier release of reacted CO 2 , producing a more effective turnover of reactants at the catalyst surface.

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Section: Discussionmentioning

confidence: 99%

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Deganello¹,

Giannici²,

Martorana³

et al. 2006

J. Phys. Chem. B

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“…The possibility of forming surface defects in the TiO2 supports in our study exists. This process can occur through H2 spillover during reduction of cobalt crystallites 29 .…”

Section: Methodsmentioning

confidence: 99%

Sintering Behavior of TiO₂-Supported Model Cobalt Fischer–Tropsch Catalysts under H₂ Reducing Conditions and Elevated Temperature

Xaba

Villiers

2016

Ind. Eng. Chem. Res.

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ABSTRACT:The sintering of model TiO2-supported cobalt catalysts has been studied. The TiO2 supports used were anatase, P25 (85% anatase-15% rutile) and rutile. The catalysts were characterized at each stage of treatment. These treatment stages were calcination, reduction and sintering. It was found that the TiO2 support does not influence the Co3O4 crystallite and particle size as shown by powder x-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. The reduction of the cobalt catalysts and bare supports was studied by temperature programmed reduction (TPR). It was found that the bare supports were not as inert as expected. The supports showed minor reduction as seen in the H2 consumption. All the cobalt catalysts showed a two-step reduction. Sintering of anatase-supported cobalt was shown to be the most substantial with P25-and rutile-supported showing a lower sintering tendency; P25-supported cobalt being the most stable based on TEM measurements. Sintering kinetics based on the Generalized Power law Expression (GPLE) model, showed that sintering of anatase-supported cobalt is the most rapid with a large sintering rate constant. Sintering of P25-supported cobalt is the lowest, shown by the lowest sintering rate constant. The study has conclusively shown the effect of the catalyst support phase. The study has also shown that the use of high surface area supports is not necessarily the only answer to preventing sintering. The phase of the catalyst support is also important.

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“…The effects of so-called strong metal-support interactions (SMSI) have received considerable attention ever since the original discovery by Tauster, et al [1], and these effects induced by high temperature reduction treatments (typically T redn ≥723 K) are generally considered to be associated with reducible supports such as TiO 2 [2], NbO 5 [3] and, especially CeO 2 [4,5]. Catalysts supported on reducible oxides have shown interesting catalytic and chemisorption properties, such as a decrease in H 2 chemisorption ability [6], suppression of alkane hydrolysis activity, increase in CO hydrogenation activity [7], and improvement in selectivity of crotyl alcohol for crotonaldehyde hydrogenation [8][9][10] when catalysts are subjected to high temperature reduction (> 773 K).…”

Section: Introductionmentioning

confidence: 99%

“…Catalysts supported on reducible oxides have shown interesting catalytic and chemisorption properties, such as a decrease in H 2 chemisorption ability [6], suppression of alkane hydrolysis activity, increase in CO hydrogenation activity [7], and improvement in selectivity of crotyl alcohol for crotonaldehyde hydrogenation [8][9][10] when catalysts are subjected to high temperature reduction (> 773 K). Electron microscopy studies have shown that after high temperature reduction, partially reduced oxide species migrate, and decorate the metal surface [4][5][6]11,12]. Bernal, et al have shown that in the case of a Pt/CeO 2 catalyst this decoration occurs at a reduction temperature of 973 K and CePt 5 particles are formed at temperatures of 1173 K [13].…”

Section: Introductionmentioning

confidence: 99%

Effect of Sn addition to Pt/CeO2–Al2O3 and Pt/Al2O3 catalysts: An XPS, 119Sn Mössbauer and microcalorimetry study

Serrano‐Ruiz

Huber

Sánchez-Castillo

et al. 2006

Journal of Catalysis

136

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The effect of Sn addition to Pt/CeO 2 -Al 2 O 3 and Pt/Al 2 O 3 catalysts was studied with X-ray photoelectron spectroscopy (XPS), 119 Sn Mössbauer spectroscopy and adsorption microcalorimetry of CO at room temperature. Catalysts were reduced in situ at 473 ("non-SMSI state") and 773 K ("SMSI state"). 119 Sn Mössbauer and XPS results indicated that the presence of cerium in bimetallic catalysts inhibited reduction of tin.Furthermore, it was found that tin facilitated reduction of cerium (IV) to cerium (III).Microcalorimetric analysis indicated that cerium addition caused the appearance of a more heterogeneous distribution of active sites, whereas tin addition led to a higher homogeneity of these sites.

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Some contributions of electron microscopy to the characterisation of the strong metal–support interaction effect

Cited by 186 publications

References 57 publications

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Sintering Behavior of TiO₂-Supported Model Cobalt Fischer–Tropsch Catalysts under H₂ Reducing Conditions and Elevated Temperature

Effect of Sn addition to Pt/CeO2–Al2O3 and Pt/Al2O3 catalysts: An XPS, 119Sn Mössbauer and microcalorimetry study

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Some contributions of electron microscopy to the characterisation of the strong metal–support interaction effect

Cited by 186 publications

References 57 publications

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce0.6Zr0.4O2

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce0.6Zr0.4O2

Sintering Behavior of TiO2-Supported Model Cobalt Fischer–Tropsch Catalysts under H2 Reducing Conditions and Elevated Temperature

Effect of Sn addition to Pt/CeO2–Al2O3 and Pt/Al2O3 catalysts: An XPS, 119Sn Mössbauer and microcalorimetry study

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Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Sintering Behavior of TiO₂-Supported Model Cobalt Fischer–Tropsch Catalysts under H₂ Reducing Conditions and Elevated Temperature