Reduction of CeO<sub>2</sub>by hydrogen. Magnetic susceptibility and Fourier-transform infrared, ultraviolet and X-ray photoelectron spectroscopy measurements

Laachir, A.; Perrichon, V.; Badri, Ahmed; Lamotte, J.; Catherine, E.; Lavalley, J.C.; Fallah, Jaâfar El; Hilaire, L.; Normand, F. Le; Quéméré, Eric; Sauvion, Guy Noël; Touret, Olivier

doi:10.1039/ft9918701601

Cited by 593 publications

(398 citation statements)

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“…The presence of Ce 3+ is observed even for the support reference sample, without the Co 3 O 4 , and in all cases it can be accounted for by the oxygen release upon heat treatment of the catalysts [49]. It should be noted, however, that the relative amount of Ce 3+ increases with the content of cobalt spinel loading (Table 1), in line with the TPR results.…”

Section: Spectroscopic Xps Characterizationsupporting

confidence: 77%

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Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Grzybek

Stelmachowski

Gudyka

et al. 2016

Applied Catalysis B: Environmental

106

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dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: the role of the interface periphery, Applied Catalysis B, Environmental http://dx.doi.org/10. 1016/j.apcatb.2015.07.027 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The catalytic tests in deN 2 O reaction revealed that the 10 wt.% of cobalt spinel in supported system is able to reproduce the activity of bare Co 3 O 4 catalyst. However, it was found that the catalyst with the lowest content of Co 3 O 4 equal to 1 wt.% exhibits the highest apparent reaction rate per mass of the spinel active phase. The observed activity was explained basing on the transmission electron microscopy analysis in terms of the dispersion of spinel phase over ceria support. A simple model that accounts for the observed strong dispersion effect is proposed. It consists in a two-step mechanism, where N 2 O is dissociated on the spinel nanograins and the resultant oxygen species are preferentially recombined at the Co 3 O 4 /CeO 2 interface periphery.

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Section: Spectroscopic Xps Characterizationsupporting

confidence: 77%

“…The peak at 529.3 eV is assigned to the lattice O 2-oxygen ions, while the second, less intense peak above 531 eV is usually assigned to surface hydroxyl groups, carbonates/adsorbed CO 2 , etc. [49]. The position of the lattice oxygen peak does not change upon addition of different amounts of the Co 3 O 4 phase.…”

Section: Spectroscopic Xps Characterizationmentioning

confidence: 97%

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Grzybek

Stelmachowski

Gudyka

et al. 2016

Applied Catalysis B: Environmental

106

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“…The band at 2130 cm -1 may be assigned to CO adsorbed to positively charged gold species [19,53], but care has to be taken because this band overlaps with the band due to CO adsorption to Ce 3? centers [54,55]. The band at 2116 cm -1 is due to the adsorption of CO to metallic gold [56].…”

Section: Resultsmentioning

confidence: 99%

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

et al. 2011

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The interaction of gold atoms with CeO 2 nanocrystals having rod and cube shapes has been examined by cyanide leaching, TEM, TPR, CO IR and X-ray absorption spectroscopy. After deposition-precipitation and calcination of gold, these surfaces contain gold nanoparticles in the range 2-6 nm. For the ceria nanorods, a substantial amount of gold is present as cations that replace Ce ions in the surface as follows from their first and second coordination shells of oxygen and cerium by EXAFS analysis. These cations are stable against cyanide leaching in contrast to gold nanoparticles. Upon reduction the isolated Au atoms form finely dispersed metal clusters with a high activity in CO oxidation, the WGS reaction and 1,3-butadiene hydrogenation. By analogy with the very low activity of reduced gold nanoparticles on ceria nanocubes exposing the {100} surface plane, it is inferred that the gold nanoparticles on the ceria nanorod surface also have a low activity in such reactions. Although the finely dispersed Au clusters are thermally stable up to quite high temperature in line with earlier findings (Y. Guan and E. J. M. Hensen, Phys Chem Chem Phys 11:9578, 2009), the presence of gold nanoparticles results in their more facile agglomeration, especially in the presence of water (e.g., WGS conditions). For liquid phase alcohol oxidation, metallic gold nanoparticles are the active sites. In the absence of a base, the O-H bond cleavage appears to be rate limiting, while this shifts to C-H bond activation after addition of NaOH. In the latter case, the gold nanoparticles on the surface of ceria nanocubes are much more active than those on the surface of nanorod ceria.

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“…The spectra in this figure were measured after oxidation in pure O 2 at 673 K to remove a majority of carbonates, after which the samples were cooled in flowing He. For pure ceria, the peaks observed at 3740, 3700, and 3635 cm -1 have been assigned to stretches of uni-dentate, bi-dentate, and tri-dentate hydroxyls [19], while the broad band centered at 3510 cm -1 is believed to correspond to adsorbed water. The uni-dentate and bi-dentate hydroxyls are almost completely removed by the addition of 1.25 wt% Mo, spectrum e), suggesting that the Mo ions react with hydroxyl sites on the ceria surface.…”

Section: Provide Insights Into Howmentioning

confidence: 99%

Deactivation of the water–gas-shift activity of Pd/ceria by Mo

Zhao

Luo

Gorte

2004

Journal of Catalysis

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The effect of surface Mo on the water-gas-shift (WGS) activity of Pd/ceria was studied. A series of 1-wt% Pd catalysts, with varying Mo content, were prepared from supports obtained by aqueous impregnation of (NH 4 ) 2 MoO 4 onto ceria. Rates were found to decrease linearly with Mo coverage up to 1.8 Mo/nm 2 and were 10% of that on Pd/ceria after the addition of this amount of Mo. TPD studies with 2-propanol on the Mo-containing ceria demonstrate a relationship between the loss of WGS activity and ceria sites that decompose the alcohol to propene and water. FTIR measurements suggest that Mo ions exchange with surface hydroxyls on ceria and that carbonates are not formed on ceria surfaces that have 1.8 Mo/nm 2 . The results from CO-O 2 pulse measurements suggest that the Mo-containing surface is much harder to reduce than pure ceria. Raman spectra of the Mo-containing ceria show features associated with molybdena only for Mo coverages greater than 1.8 Mo/nm 2 . The implications of these results for understanding WGS activity on Pd/ceria are discussed. KeywordsCeria, Pd, Molybdena, Water-gas-shift reaction, 2-propanol

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Reduction of CeO₂by hydrogen. Magnetic susceptibility and Fourier-transform infrared, ultraviolet and X-ray photoelectron spectroscopy measurements

Cited by 593 publications

References 28 publications

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

Deactivation of the water–gas-shift activity of Pd/ceria by Mo

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Reduction of CeO2by hydrogen. Magnetic susceptibility and Fourier-transform infrared, ultraviolet and X-ray photoelectron spectroscopy measurements

Cited by 593 publications

References 28 publications

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Gold Stabilized by Nanostructured Ceria Supports: Nature of the Active Sites and Catalytic Performance

Deactivation of the water–gas-shift activity of Pd/ceria by Mo

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Reduction of CeO₂by hydrogen. Magnetic susceptibility and Fourier-transform infrared, ultraviolet and X-ray photoelectron spectroscopy measurements