<i>In situ</i> environmental HRTEM discloses low temperature carbon soot oxidation by ceria–zirconia at the nanoscale

Aneggi, Eleonora; Llorca, Jordi; Trovarelli, Alessandro; Aouine, M.; Vernoux, P.

doi:10.1039/c8cc09011d

Cited by 22 publications

(15 citation statements)

References 12 publications

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“…This is particularly evident in ceria crystallites below 5 nm [19][20][21][22]. In this case, Ce 3+ sites are not necessarily associated to an oxygen vacancy and can act as a centre for adsorption of oxygen to yield active oxygen species and thus boosting oxygen storage activity and low-temperature oxidation activity [23][24][25][26]. There is a consensus that the preparation of active ceria-based catalysts requires the presence of defective surface sites, either Ce 3+ or Ce 4+ associated with a vacancy, which can act as centres to maximize active oxygen adsorption/release under operative conditions.…”

Section: Ceria In Catalysismentioning

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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Section: Ceria In Catalysismentioning

confidence: 99%

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

et al. 2020

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“…This is not representative of the real application, but it is a good reference for a high degree of redox interaction that can be obtained between carbon and catalyst, and is useful in the understanding of the mechanism of reaction and on the intrinsic activity of reducible materials. This contact is characterized by a different morphology, where a layer of soot forms a thin shell covering ceria-zirconia crystallite cores promoting interactions at a nanoscale at the ceria-zirconia/carbon interface [40,41]. The different contact modes are represented in Scheme 1.…”

Section: Textural Structural and Redox Characterization Of Soot/catalyst Mixturesmentioning

confidence: 99%

“…Here we have investigated the soot combustion reaction over Ce 0.8 Zr 0.2 O 2 and ZrO 2 (as an example of reducible and non-reducible materials, respectively), with a specific focus on the influence of the atmosphere of reaction (from inert gas to air) and of the type of carbon/catalyst interaction by varying the way soot and catalyst were put into contact. For this reason, three different contact conditions were employed with varying degrees of carbon/catalyst interactions, which were previously characterized at a nanoscale level [40,41]. This allowed us to monitor the oxidation ability of modified ceria at low oxygen pressure, as a function of the degree of interaction between carbon soot and surface ceria oxygens, and verify that this formulation could represent a good starting point for the development of catalysts for GPF systems.…”

Section: Introductionmentioning

confidence: 99%

Potential of Ceria-Zirconia-Based Materials in Carbon Soot Oxidation for Gasoline Particulate Filters

Aneggi

Trovarelli

2020

Catalysts

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ZrO2 and Ce0.8Zr0.2O2 mixed oxides were prepared and tested in the oxidation of carbon soot at different oxygen partial pressures and degrees of catalyst/soot contact to investigate their activity under typical gasoline direct injection (GDI) operating conditions. Under reductive atmospheres, generation of oxygen vacancies occurs in Ce0.8Zr0.2O2, while no reduction is observed on ZrO2. Both materials can oxidize carbon under high oxygen partial pressures; however, at low oxygen partial pressures, the presence of carbon can contribute to the reduction of the catalyst and formation of oxygen vacancies, which can then be used for soot oxidation, increasing the overall performance. This mechanism is more efficient in Ce0.8Zr0.2O2 than ZrO2, and depends heavily on the interaction and the degree of contact between soot and catalyst. Thus, the ability to form oxygen vacancies at lower temperatures is particularly helpful to oxidize soot at low oxygen partial pressures, and with higher CO2 selectivity under conditions typically found in GDI engine exhaust gases.

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“…In particular, the metal-support interaction established between Pd and cerium dioxide has shown excellent properties for the activation of C-H bonds in the methane molecule, which originates from the oxygen storage-release properties of ceria and the stabilization of oxidized Pd species [16]. In addition, ceria facilitates the oxidation and removal of any soot deposited [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Methane Partial Oxidation over Pd Supported on CeO2: Effect of the Preparation Method and Precursors

2021

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The catalytic production of syngas by the partial oxidation of methane (POM) was investigated over Pd supported on ceria (0.5–2 Pd wt.%) prepared by incipient wetness impregnation and by mechanochemical methods. The performance of the Pd/CeO2 catalyst prepared by milling CeO2 and Pd acetate was superior to that prepared by milling CeO2 and Pd nitrate and to Pd/CeO2 prepared by impregnation from Pd acetate. The best catalytic activity of the Pd/CeO2 catalyst prepared from CeO2 and Pd acetate was obtained by milling at 50 Hz for 5 min. Two-step combustion and reforming reaction mechanism were identified. Remarkably, methane conversion increased progressively with Pd loading for the catalysts prepared by incipient wetness impregnation, whereas low metal loading showed better conversion of methane for the catalysts prepared by ball milling using Pd acetate. This was explained in terms of an impressive dispersion of Pd species with a strong interaction with the surface of ceria, as deduced from transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy characterization, which revealed a large quantity of highly oxidized species at the surface.

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In situ environmental HRTEM discloses low temperature carbon soot oxidation by ceria–zirconia at the nanoscale

Abstract: In situ environmental transmission electron microscopy discloses room temperature carbon soot oxidation by ceria–zirconia at the nanoscale.

Cited by 22 publications

References 12 publications

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

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

Potential of Ceria-Zirconia-Based Materials in Carbon Soot Oxidation for Gasoline Particulate Filters

Low-Temperature Methane Partial Oxidation over Pd Supported on CeO2: Effect of the Preparation Method and Precursors

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