The SAMBA quick-EXAFS monochromator: XAS with edge jumping

Fonda, Emiliano; Rochet, Amélie; Ribbens, M.; Barthe, Laurent; Belin, Stéphanie; Briois, Valérie

doi:10.1107/s0909049512009703

Cited by 83 publications

(71 citation statements)

References 35 publications

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“…Co K‐edge XAS data were recorded on the SAMBA beamline at the SOLEIL synchrotron. Time resolved in situ Quick‐XAS measurements were performed in transmission mode with three ionization chambers filled with gaseous N 2 . The Si(1 1 1) channel‐cut crystal was tuned to a Bragg angle near to the Co K‐edge energy (13.9°) whereas the cam‐driven tilt table supporting the channel‐cut was allowed to oscillate with an amplitude of 2.2° around this value.…”

Section: Methodsmentioning

confidence: 99%

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

et al. 2017

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The effect of sol–gel alumina characteristics on the supported Co catalyst properties was investigated at the different steps of catalyst preparation. Porous alumina with variable surface reactivity were prepared from the sol–gel transition and the spinodal decomposition induced by polymers. The hydrophobicity of polymer or the calcination temperature controls the amount of the hydroxyl groups. The dried catalysts are composed of cobalt alumina hydrotalcite‐like compounds up to 64 %. After calcination, higher proportions of CoAl2O4 are observed in the alumina presenting a greater content of hydroxyl and hydrotalcite. The Co speciation during activation investigated by Quick X‐ray absorption spectroscopy evidences that both Co3O4 and CoAl2O4 are first fully reduced to CoO and then partially transformed into point‐like Co0 nucleus. The catalysts were highly active in the ethanol steam reforming reaction; however, coke deposition leads to deactivation. This deleterious effect was minimized for catalysts operating with a CoO/Co0 ratio close to 1:3.

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Section: Methodsmentioning

confidence: 99%

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

et al. 2017

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“…Fast in situ acquisitions were obtained using aQ uick-XAS monochromator equipped with ac hannel-cut Si(111)c rystal the oscillating movement of which was set to acquire one spectrum every 0.5 s. [47] The powdered sample was placed into ad edicated in situ cell, [48] positioned between two Ohken ionization chambers filled with nitrogen, for detection of the incident and transmitted X-rays. This cell enabled catalyst treatments to be performed under controlled conditions of temperature and gas flow.…”

Section: Characterization Of the Catalystsmentioning

confidence: 99%

Correlation between Structural and Catalytic Properties of Copper Supported on Porous Alumina for the Ethanol Dehydrogenation Reaction

et al. 2015

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Carbon nanofibers (CNFs) were functionalized with aryl sulfonic acid groups using in situ diazonium coupling. The use of diazonium coupling yielded an acidic carbon material, in which the introduced acidic groups are readily accessible to the triglyceride substrate. The material is an efficient catalyst for the transesterification of triolein and methanol, outperforming conventional sulfonated carbons in both stability and activity per acid site. Upon comparing CNFs with varying degrees of functionalization, a linear correlation between sulfonic acid sites and catalytic performance was found.

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“…Additionally, XAS measurements as a function of temperature on pellets of polycrystalline LuFe 2 O 4 (187-290 K), YFe 2 O 4 (160-265 K), and LuCoFeO 4 were also performed in transmission at the SAMBA beamline of the SOLEIL synchrotron. In this case, a Si(220) double-crystal monochromator was used, and the spectra were also recorded in the quick energy scanning mode [47]. Both XANES and EXAFS unpolarized spectra were equal to those measured at CLAESS.…”

Section: Methodsmentioning

confidence: 99%

Strong local lattice instability in hexagonal ferritesRFe2O4(R= Lu,Y,Yb) revealed by x-ray absorption spe

et al. 2014

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We present here an x-ray absorption study of the RFe 2 O 4 series (LuFe 2 O 4 , YFe 2 O 4 , YbFe 2 O 4 , and LuCoFeO 4 ) at the Fe K-edge. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectra were measured at temperatures ranging from 100 K to 390 K crossing the charge ordering (CO) transition temperatures on both isotropic and oriented powder samples. Unpolarized and polarized x-ray absorption spectra with the x-ray polarization parallel and perpendicular to the hexagonal c axis were obtained separately. The XANES spectra show almost no dependence with either polarization or temperature. This indicates that, in contrast to its average crystallographic structure, the local electronic and geometrical state of the Fe atom is barely anisotropic, and it remains the same above and below the proposed CO. Moreover, the linear combination of two spectra corresponding to the pure ionic states Fe 2+ and Fe 3+ does not fit to the experimental XANES of either LuFe 2 O 4 , YFe 2 O 4 , or YbFe 2 O 4 , discarding total ionic segregation in favor of an intermediate mixed valence state. The maximum charge disproportionation compatible with the XANES spectra is 0.5 ± 0.1 electrons in the whole temperature range. The polarized EXAFS spectra have allowed us to analyze the local structure separating the different contributions mixed up in the polycrystal. Best-fit results show that the five oxygen atoms of the first coordination shell are at nearly the same distance but with a large Debye-Waller factor. Neither the interatomic distances nor the Debye-Waller factors of the first oxygen coordination shell change with temperature, indicating that the dynamical structural distortion of the high-temperature symmetric hexagonal phase freezes upon cooling down. Thus, the local structure instability of the mixed valence is in the origin of the structural transitions.

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The SAMBA quick-EXAFS monochromator: XAS with edge jumping

Cited by 83 publications

References 35 publications

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

Correlation between Structural and Catalytic Properties of Copper Supported on Porous Alumina for the Ethanol Dehydrogenation Reaction

Strong local lattice instability in hexagonal ferritesRFe2O4(R= Lu,Y,Yb) revealed by x-ray absorption spe

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