Oxygen storage capacity improvement using CeO2-ZrO2 mixed oxides in three way catalysts

Finocchio, Elisabetta; Daturi, Marco; Binet, Claude; Lavalley, J.C.; Flly, Fabienne; Perrichon, V.; Vidal, Hilario; Kašpar, Jan; Graziani, M.; Blanchard, G.

doi:10.1016/s0167-2991(99)80076-7

Cited by 11 publications

(9 citation statements)

References 7 publications

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“…The europium-doped CZE0.5 and CZE0.8 samples show typical TPR-H 2 profiles with a main reduction peak at 690 and 590 °C, respectively. The results are similar to TPR-H 2 profiles published by other researchers for similar materials. , …”

Section: Resultssupporting

confidence: 91%

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

et al. 2015

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Despite the wide range of industrial applications for ceria-zirconia mixed oxides (Ce x Zr 1−x O 2 ), the complex correlation between their atomic structure and catalytic performance is still under debate. Catalytically interesting Ce x Zr 1−x O 2 nanomaterials can form homogeneous solid solutions and, depending on the composition, show phase separation under the formation of small domains. The characterization of homogeneity and atomic structure of these materials remains a major challenge. High-resolution emission spectroscopy recorded under cryogenic conditions using Eu 3+ as a structural probe in doped CeZrO 2 nanoparticles offers an effective way to identify the different atomic environments of the Eu 3+ dopants and, subsequently, to monitor structural parameters of the ceria-zirconia mixed oxides. It is found that, in stoichiometric CeZrO 2 :Eu 3+ , phase separation occurs at elevated temperatures beginning with the gradual formation of (pseudo)cubic crystallites in the amorphous materials at 500 °C and a sudden phase separation into tetragonal, zirconia-rich and cubic, ceria-rich domains over 900 °C. The presented technique allows us to easily monitor subtle changes even in amorphous, high surface area samples, yielding structural information not accessible by conventional techniques such as X-ray diffraction (XRD) and Raman. Moreover, in reference experiments investigating the reducibility of largely unordered Ce 0.2 Zr 0.8 O 2 :Eu 3+ , the main reduction peak in temperature-programmed reduction measurements appeared at exceptionally low temperatures below 200 °C, thus suggesting the outstanding potential of this oxide to activate catalytic oxidation reactions. This effect was found to be dependent on the amount of Eu 3+ dopant introduced into the CeZrO 2 matrix as well as to be connected to the atomic structure of the catalyst material.

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Section: Resultssupporting

confidence: 91%

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

et al. 2015

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“…Time-resolved X-ray diffraction (TR-XRD) and NAP-XPS measurements showed important oxidation state changes of the catalysts under reaction conditions, being metallic Cu and partially reduced ceria the active phase for the reaction. Studies with NAP-XPS also revealed a more effective CO 2 dissociative activation at high temperature and a preferential formation of bidentate carbonate and formate intermediates over ceria nanorods, which mainly expose (110) terminations. Finally, Winter and colleagues [138] reported a study of CO 2 hydrogenation over CeO 2 -supported Ni catalysts with different metal loading.…”

Section: Co 2 Hydrogenationmentioning

confidence: 95%

“…A well-known method to notably enhance cerium oxide redox activity is the addition of 3d transition metals to its unit cell to form solid solutions with an ordered atomic arrangement [3,102]. For instance, it has been demonstrated that Ce 1−x M x O 2−y mixed oxides (where M = Cr [103,104], Mn [104][105][106], Fe [104,106], Co [104][105][106], Ni [105,106], Cu [107,108], Zr [109][110][111], La [112][113][114]) exhibit lower reduction temperatures than pure ceria. The incorporation of noble metals to ceria to generate Ce 1−x M' x O 2−y mixed oxides (M' = Ru [115], Rh [116,117], Pd [117,118]) has also demonstrated to efficiently promote reducibility of cerium ions and greatly decrease the reduction temperatures too [119].…”

Section: Fundamental Studiesmentioning

confidence: 99%

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

et al. 2020

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The development of better catalysts is a passionate topic at the forefront of modern science, where operando techniques are necessary to identify the nature of the active sites. The surface of a solid catalyst is dynamic and dependent on the reaction environment and, therefore, the catalytic active sites may only be formed under specific reaction conditions and may not be stable either in air or under high vacuum conditions. The identification of the active sites and the understanding of their behaviour are essential information towards a rational catalyst design. One of the most powerful operando techniques for the study of active sites is near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), which is particularly sensitive to the surface and sub-surface of solids. Here we review the use of NAP-XPS for the study of ceria-based catalysts, widely used in a large number of industrial processes due to their excellent oxygen storage capacity and well-established redox properties.

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“…This conversion is reversible upon reoxidation by adsorbing O 2 at room temperature. 26,29 Upon reducing between 773 and 873 K, the overall intensity of ν(OC) bands falls abruptly indicating a sintering of the material which occurs under the reducing environment. 30 The sample was in fact pretreated at 873 K under oxidizing conditions, which does not affect its texture.…”

Section: ) Vibrations In This Workmentioning

confidence: 99%

Reduction of High Surface Area CeO₂−ZrO₂ Mixed Oxides

et al. 2000

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The objective of this study was to examine the mechanism of the reduction by hydrogen of ceria-zirconia (CZ) mixed oxides having a high BET surface area (100 m 2 g -1 ). Three methods were used in parallel to assess the Ce 3+ content, the surface and bulk oxygen vacancy concentrations, and the resulting oxygen storage capacity (OSC): temperature programmed reduction, Fourier transform infrared (FT-IR) measurements of methanol adsorbed on the reduced surfaces, and a Faraday microbalance to determine the magnetic susceptibility of the reduced oxides. The three methods conclude that the introduction of zirconium into the ceria lattice has a positive influence on the OSC. Compared to pure ceria, the CZ mixed oxides exhibit better redox properties, with a lower temperature of initial reduction and a higher reduction percentage for all compositions. The reducibility increases with the zirconium content, however the OSC per gram of solid is practically the same for Zr contents between 20% and 50%. The reduction process very rapidly involves the bulk, but a treatment at room temperature under oxygen of the reduced samples oxidizes them almost completely. However, the FT-IR results underline the differing behavior of ceria for the distinct surface and bulk reduction processes.

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Oxygen storage capacity improvement using CeO2-ZrO2 mixed oxides in three way catalysts

Cited by 11 publications

References 7 publications

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

Reduction of High Surface Area CeO₂−ZrO₂ Mixed Oxides

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Oxygen storage capacity improvement using CeO2-ZrO2 mixed oxides in three way catalysts

Cited by 11 publications

References 7 publications

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline CexZr1–xO2:Eu3+Catalyst Materials

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline CexZr1–xO2:Eu3+Catalyst Materials

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

Reduction of High Surface Area CeO2−ZrO2 Mixed Oxides

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Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline Ce_xZr_1–xO₂:Eu³⁺Catalyst Materials

Reduction of High Surface Area CeO₂−ZrO₂ Mixed Oxides