Structure-activity relationship in Pd/CeO2 methane oxidation catalysts

Colussi, Sara; Fornasiero, Paolo; Trovarelli, Alessandro

doi:10.1016/s1872-2067(19)63510-2

Cited by 70 publications

(45 citation statements)

References 140 publications

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“…However, CH 4 is also the second most important human-induced greenhouse gas, and its global warming potential is more than 20 times that of CO 2 . Thus, the catalytic oxidation of CH 4 is of great importance to make the best use of clean energy and reduce the greenhouse effect. , As one of the most active catalysts for CH 4 oxidation, , cerium dioxide (CeO 2 )-supported Pd catalyst exhibits excellent performance for the oxidation of CH 4 . , Identifying the active species of Pd/CeO 2 catalyst to understand its catalytic mechanism for CH 4 oxidation is essential to improve the catalytic activities of Pd-based catalysts. However, as CeO 2 has a superior oxygen storage capacity, the valence change of Ce 4+ /Ce 3+ could occur during the redox reaction process, − which may result in complex Pd–CeO 2 interactions, leading to different Pd species .…”

Section: Introductionmentioning

confidence: 99%

Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

et al. 2021

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Pd/CeO 2 has attracted great attention owing to its unique activity for methane catalytic oxidation; however, the active sites for CH 4 catalytic oxidation still remain elusive, which affects the comprehensive understanding of the catalytic mechanism. In this work, the structures of PdO x nanoparticles (NPs) loaded on octahedrons, cubes, and rods of nanocrystal CeO 2 supports were systematically studied by Cs-corrected HRTEM/STEM, XPS, and Raman spectroscopy. Our results indicate that the Pd species on CeO 2 supports are morphology-dependent: PdO NPs (Pd 2+ ) on octahedrons, PdO x (x = 1−2) clusters (1−2 nm) on cubes, and dispersed Pd 4+ ions on the CeO 2 rods. Additionally, the chemical states of Pd can be tuned in oxidizing/reducing atmospheres via interactions between Pd and CeO 2 . Detailed studies reveal that the Pd 2+ species are the active centers for the catalytic oxidation of methane. The activity of Pd 0 could be ascribed to Pd 2+ produced through the gradual oxidation of Pd 0 during the CH 4 oxidation. Further, Pd 4+ in the CeO 2 lattice is inactive for CH 4 oxidation. In situ Fourier transform infrared spectroscopy results suggest that the mechanism of CH 4 oxidation reaction on PdO x /CeO 2 follows the Mars−van Krevelen mechanism, and adsorbed CO can be produced in CH 4 decomposition over Pd 2+ in the absence of gas-phase oxygen. As revealed by density functional theory calculations, the incomplete coordination of Pd 2+ ions and adjacent oxygen atoms has excellent activity in cracking the C−H bond of CH 4 , which leads to high methane oxidation ability.

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Section: Introductionmentioning

confidence: 99%

Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

et al. 2021

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“…Due to its unique properties, palladium (Pd) plays an important role in the catalytic industry. − In combination with CeO 2 , Pd is used as an active component in many catalytic processes, including exhaust gas after-treatment. − However, the nature of the Pd species responsible for the high activity of the Pd/CeO 2 catalysts in hydrocarbon or CO oxidation reactions still remains a topic of discussion. The authors consider different Pd species to be active in the catalytic reactions: metallic Pd nanoparticles, coordination-unsaturated Pd 2+ on CeO 2 , isolated Pd atoms in the form of Pd 1 O and Pd 1 O 2 on CeO 2 , , PdO x clusters, − PdO nanoparticles, , Pd x Ce 1– x O 2−δ solid solutions, ,,, and Pd@CeO 2 core–shell structures. , The charge state of Pd in the abovementioned species does not exceed +2.…”

Section: Introductionmentioning

confidence: 99%

Probing of Pd⁴⁺ Species in a PdO_x–CeO₂ System by X-Ray Photoelectron Spectroscopy

et al. 2021

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The oxidized palladium nanoparticles comprising Pd4+ species were prepared by radio frequency (RF) discharge in an O2 atmosphere and analyzed with X-ray photoelectron spectroscopy. PdO x particles were deposited on CeO2 or the reference support (Ta2O5) with variation of the RF sputtering time. Regardless of the used support, small PdO x particles (d < 1 nm) contained only Pd2+ species, while an increase of the particle size led to the appearance of the additional oxidized Pd statePd4+. The stabilization of Pd4+ on the surface of defect PdO particles was proposed. The Pd4+ species in the PdO x /CeO2 system was stable during heating in ultra-high vacuum conditions up to 250 °C. Pd4+ species demonstrated a high reaction probability toward CO oxidation at room temperature. However, a transition from the relatively inert support (Ta2O5) to the reducible oxide (CeO2) did not lead to a significant improvement of the Pd4+ reaction probability. Pd4+ species could not be recovered by the exposure of the reduced systems to molecular oxygen at room temperature. The obtained results bring new insights into consideration of Pd4+ species as active sites for oxidation processes at low temperatures.

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“…Mixing of Pd into the ceria lattice provides a coordination environment for Pd δ+ species that enables facile alternation between Pd 0 /Pd 2+ /Pd 4+ oxidation states, therefore creating highly reducible sites ideal for methane activation. Results indicate that incorporated Pd 4+ ions in ceria provide higher catalytic activity for methane oxidation than large Pd particles or large palladium oxide particles. ,− …”

Section: Catalyst Developmentmentioning

confidence: 99%

Active Components of Catalysts of Methane Conversion to Synthesis Gas: Brief Perspectives

Zagaynov

2021

Energy Fuels

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Methane transformation into more valuable products has attracted extensive attention. Synthesis gas is an important intermediate product in the chemical industry. Several syngas production methods are available, depending on the purpose of the industrial application. A major limitation of the processes is the rapid deactivation of the catalyst, which has been commonly attributed to the sintering of the active sites of catalyst and carbon formations on these sites, induced by methane decomposition and CO disproportionation. The catalyst consists of an active component and support. Ceria-based systems have been extensively employed as the support because of their unique redox properties and high oxygen storage capacity. The most promising approach is to design an excellent active site of the catalyst, based on noble or transition metals. A comparison of perspective active components, especially polymetallic components, is considered here.

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Structure-activity relationship in Pd/CeO2 methane oxidation catalysts

Cited by 70 publications

References 140 publications

Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

Probing of Pd⁴⁺ Species in a PdO_x–CeO₂ System by X-Ray Photoelectron Spectroscopy

Active Components of Catalysts of Methane Conversion to Synthesis Gas: Brief Perspectives

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Structure-activity relationship in Pd/CeO2 methane oxidation catalysts

Cited by 70 publications

References 140 publications

Elucidation of Active Sites for CH4 Catalytic Oxidation over Pd/CeO2 Via Tailoring Metal–Support Interactions

Elucidation of Active Sites for CH4 Catalytic Oxidation over Pd/CeO2 Via Tailoring Metal–Support Interactions

Probing of Pd4+ Species in a PdOx–CeO2 System by X-Ray Photoelectron Spectroscopy

Active Components of Catalysts of Methane Conversion to Synthesis Gas: Brief Perspectives

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Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

Elucidation of Active Sites for CH₄ Catalytic Oxidation over Pd/CeO₂ Via Tailoring Metal–Support Interactions

Probing of Pd⁴⁺ Species in a PdO_x–CeO₂ System by X-Ray Photoelectron Spectroscopy