Soft X-ray absorption spectroscopy in heterogeneous catalysis

Bazin, Dominique; Guczi, L.

doi:10.1016/s0926-860x(00)00895-4

Cited by 36 publications

(30 citation statements)

References 109 publications

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“…31 It is thus not easy to predict the heat of adsorption on the present NPs, but in any case, a strong adsorption on Co sites can be expected. Formation of Cu−carbonyls is very unlikely, as density functional theory calculations suggest a very weak Cu− CO bond (6 kcal/mol), 38 while Co−carbonyls (such as Co 2 (CO) 8 , HCo(CO) 4 , or Co 4 (CO) 12 ) are stable.…”

Section: Resultsmentioning

confidence: 99%

Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Carenco¹,

Tuxen²,

Chintapalli³

et al. 2013

J. Phys. Chem. C

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ABSTRACT:The structure and composition of core−shell CuCo nanoparticles were found to change as a result of cleaning pretreatments and when exposed to syngas (CO + H 2 ) at atmospheric pressure. In situ X-ray absorption and photoelectron spectroscopies revealed the oxidation state of the particles as well as the presence of adsorbates under syngas. Transmission electron microscopy was used for ex situ analysis of the shape, elemental composition, and structure after reaction. The original core−shell structure was found to change to a hollow CuCo alloy after pretreatment by oxidation in pure O 2 and reduction in pure H 2 . After 30 min of exposure to syngas, a significant fraction (5%) of the particles was strongly depleted in cobalt giving copper-rich nanoparticles. This fraction increased with duration of syngas exposure, a phenomenon that did not occur under pure CO or pure H 2 . This study suggests that Co and Cu can each individually contribute to syngas conversion with CuCo catalysts.

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Section: Resultsmentioning

confidence: 99%

Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Carenco¹,

Tuxen²,

Chintapalli³

et al. 2013

J. Phys. Chem. C

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“…XAS is sensitive to details of the electronic structure, such as the valence level structure, symmetry, spin state, etc. The use of soft X-rays for the study in situ of cobalt catalysts was first reported by Bazin et al [20,21]. In these studies, spectra of a powder Co/SiO 2 sample were obtained in the presence of hydrogen.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Cobalt Particle Size in the CO Hydrogenation Reaction Studied by In Situ X-Ray Absorption Spectroscopy

et al. 2009

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TitleInfluence of the cobalt particle size in the CO hydrogenation reaction studied by in situ X-ray absorption spectroscopy To whom correspondence should be addressed. E-mail: MBSalmeron@lbl.govThe influence of particle size in the carbon monoxide hydrogenation reaction has been studied using cobalt nanoparticles (NP) with narrow size distribution prepared by colloidal chemistry. The surfactant covering the NP after synthesis could be removed by heating to 200-270ºC in H 2 . Soft X ray absorption spectroscopy was performed in a gas flow cell under reaction conditions of H 2 and CO at atmospheric pressure. Flow of pure hydrogen at 350ºC removed the protecting surfactant layer and reduced the NP from oxidized to metallic. The NP remained metallic during the methanation reaction with their surface covered by CO. The methanation turnover frequency of silica supported NP was found to decrease with diameter below 10 nm, while the reaction activation energy was found to be independent of NP size. H-D exchange experiments indicated that it is the dissociation of H 2 that is responsible for the observed decrease in activity with size.2 KEYWORDS. Cobalt, nanoparticles, Fischer-Tropsch, X-ray absorption (XAS), in situ studies, soft xray spectroscopy, particle size dependence.

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“…In addition, soft XAS can also be employed to study the K edge XAS of light elements such as carbon, nitrogen, and oxygen. This combination of simultaneously probing both light elements and transition metals makes soft XAS quite suitable for studying the adsorption processes in heterogeneous catalysis, which was covered in an excellent review by Bazin et al [13].…”

Section: X-ray Absorption Spectroscopy (Xas)mentioning

confidence: 99%

“…In another study, growth of gold nanoparticles was monitored with XAS by Chen et al [127]. They found that small gold nanoclusters such as Au 13 were formed immediately after the introduction of the reducing agent into the gold acidic solution. The magic number of 13 means that this cluster is probably one of the many metastable intermediates existed in the solution.…”

Section: Nanomaterials Made Ex Situmentioning

confidence: 99%

More power to X‐rays: New developments in X‐ray spectroscopy

Guo¹

2009

Laser & Photonics Reviews

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Recent developments in X-ray spectroscopy in the last decade are reviewed. A specific emphasis is placed on displaying the strong natural connection between X-ray spectroscopy and materials science. Brief explanations of several X-ray spectroscopic methods are given. X-ray spectroscopic instruments such as table-top X-ray sources are discussed in detail, whereas those employing synchrotron and other sources are briefly addressed. The spectroscopic methods and results from materials investigations are reviewed according to their positions in a 3D parameter space of time, length, and energy. New experimental measurements on atoms, molecules, nanomaterials, and bulk materials that include insulators, semiconductors, metals and magnetic materials using both static and time-resolved methods are reviewed.A typical table-top experimental setup to probe a sample using an optical pump (green color beam) -X-ray probe (purple color beam) technique. The X-ray pulses are produced by femtosecond optical pulses. Two exemplary data are displayed: One is direct imaging of plasmas generated from laser evaporation of a solid target (Imaging data) and the other is an X-ray absorption spectrum of a nickel sample (USEXAS data).

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Soft X-ray absorption spectroscopy in heterogeneous catalysis

Cited by 36 publications

References 109 publications

Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Influence of the Cobalt Particle Size in the CO Hydrogenation Reaction Studied by In Situ X-Ray Absorption Spectroscopy

More power to X‐rays: New developments in X‐ray spectroscopy

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