Tpd And Xps Studies of Co and No on Highly Dispersed PT+RH Automotive Exhaust Catalysts: Evidence for Noble Metal-Ceria Interaction

Lööf, Peter; Kasemo, Bengt Herbert; BjÖrnkvist, L.; Andersson, S.; Frestad, A.

doi:10.1016/s0167-2991(08)62983-3

Cited by 35 publications

(17 citation statements)

References 34 publications

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“…Stored oxygen is then available for reaction with CO and hydrocarbons during subsequent fuel-rich air/fuel ratio excursions. Ceria has been shown to enhance the decomposition of NO by extending the time before the noble metal catalyst is deactivated by the accumulation of surface oxygen derived from NO decomposition [67]. That is, Rh/CeO 2 is deactivated more slowly than Rh/Al 2 O 3 during NO decomposition, probably due to oxygen spillover from the noble metal to the reduced ceria.…”

Section: Resultsmentioning

confidence: 99%

Environmental catalysis

Garin

2004

Catalysis Today

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This review article was constructed around the first Algerian-French congress aimed on emerging materials which was held at Tamanrasset by the end of February 2003. The aim of this review is to point out that a lot of work has been done in heterogeneous catalysis to better understand the active sites responsible for the catalytic reactivity. Most of these researches were performed under reducible atmosphere, on metallic catalysts, to improve our knowledge about hydrocarbon reforming catalysts. Starting from this base which was recalled through various classes of important studies such as: (i) the dilution of the active sites, (ii) the use of bimetallics, (iii) the use of well-crystallised surfaces and (iv) the influence of the metal-support interactions; a development and an opening is made on the three-way catalysis and the DeNO x reactions. The objectives being to point out the very important influence of the experimental conditions and of the gas phase compositions which may induce very strong surface modifications of the initial metallic aggregates. Moreover, it will depend on the reactions, i.e. isomerisation, oxidation, reduction where the active site may also be composed of, in addition to the metallic crystallites, the participation of the oxygen of the support.A tentative for a general interpretation of the observed results is given by the use of the variations of the local density of states and of the "d" band centre energy.

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Section: Resultsmentioning

confidence: 99%

Environmental catalysis

Garin

2004

Catalysis Today

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“…It remains to be addressed if this observed linear particle decay can be accounted for by a size-dependent surface energy of the nanoparticles. Modeling the surface energy is further complicated by the size-dependent surface oxidation of the Pt nanoparticles [40][41][42].…”

Section: Discussionmentioning

confidence: 99%

Ostwald ripening in a Pt/SiO2 model catalyst studied by in situ TEM

Simonsen

Chorkendorff

Dahl

et al. 2011

Journal of Catalysis

197

202

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Sintering of Pt nanoparticles dispersed on a planar SiO 2 support was studied by in situ transmission electron microscopy (TEM). A time-lapsed TEM image series of the Pt nanoparticles, acquired during the exposure to 10 mbar synthetic air at 650 ºC, reveal that the sintering is governed by the Ostwald ripening mechanism. The in situ TEM images also provide information about the temporal evolution of the Pt particle size distribution and of the individual nanoparticle's growth or decay. The observed Pt nanoparticle changes compare well with predictions made by mean-field kinetic models for ripening, but deviations are revealed for the time-evolution for the individual nanoparticles. A better description of the individual nanoparticle ripening is obtained by kinetic models that include local correlations between neighboring nanoparticles in the atom-exchange process.

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“…In order to preserve a high Pt dispersion, the catalyst was calcined at 450 C for 4h in air, starting with a temperature ramp from room temperature with a rate of 5 C per minute to 450 C. The platinum dispersion of the final catalyst was determined by CO chemisorption (Micromeritics, ASAP2010C) at 27 C giving 65% dispersion assuming a maximum CO/Pt ratio of 0.8, which is reasonable for highly dispersed Pt particles. 17 The BET surface area (Micromeritics, Tristar) of the sample was measured to be 182 m 2 /g.…”

Section: Experimental Section Catalyst Preparation and Characterizationmentioning

confidence: 99%

In Situ Spectroscopic Investigation of Low-Temperature Oxidation of Methane over Alumina-Supported Platinum during Periodic Operation

et al. 2010

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Methane oxidation over Pt/Al 2 O 3 at transient inlet-gas conditions was studied in situ using synchronous EDXAS, FTIRS and mass spectrometry. The employed combination of experimental techniques allows for simultaneous analysis of, respectively, the electronic state of platinum, surface coverage of reaction intermediates/products and catalytic activity/selectivity.By cycling of the feed gas composition between net-oxidizing and net-reducing conditions the activity for methane oxidation can be increased as compared to continuous net-oxidising conditions. Using the white-line area of time-resolved XANES spectra, a quantitative estimation of the surface O/Pt ratio indicates the formation of an inhomogeneous surface oxide on the platinum crystallites during reaction. The obtained temporary high activity can be explained ⇤ To whom correspondence should be addressed 1 through Langmuir-Hinshelwood kinetics and may result either from the formation of a partially oxidized platinum surface that is more effective for methane dissociation or, more likely, from a period with more reactive chemisorbed oxygen prior to oxide formation.

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Tpd And Xps Studies of Co and No on Highly Dispersed PT+RH Automotive Exhaust Catalysts: Evidence for Noble Metal-Ceria Interaction

Cited by 35 publications

References 34 publications

Environmental catalysis

Environmental catalysis

Ostwald ripening in a Pt/SiO2 model catalyst studied by in situ TEM

In Situ Spectroscopic Investigation of Low-Temperature Oxidation of Methane over Alumina-Supported Platinum during Periodic Operation

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