Thermally Induced Structural Evolution of Palladium‐Ceria Catalysts. Implication for CO Oxidation

Стонкус, О. А.; Kardash, T. Yu.; Slavinskaya, Elena M.; Зайковский, В. И.; Boronin, A. I.

doi:10.1002/cctc.201900752

Cited by 29 publications

(21 citation statements)

References 90 publications

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“…Furthermore, the chemical state of Pd in Pd 1 @HEFO is then investigated by XPS analysis, and the obtained binding energy (Supplementary Fig. 6 ) is the characteristic of electron-deficient Pd 4+ 25 – 27 . This formation of electron-deficient Pd 4+ may be attributed to the electron transfer from Pd to M through Pd–O–M bonds (M = Ce, Zr, Hf, Ti, and La) in (Pd y CeZrHfTiLa)O x solid solution.…”

Section: Resultsmentioning

confidence: 99%

Entropy-stabilized single-atom Pd catalysts via high-entropy fluorite oxide supports

et al. 2020

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Single-atom catalysts (SACs) have attracted considerable attention in the catalysis community. However, fabricating intrinsically stable SACs on traditional supports (N-doped carbon, metal oxides, etc.) remains a formidable challenge, especially under hightemperature conditions. Here, we report a novel entropy-driven strategy to stabilize Pd single-atom on the high-entropy fluorite oxides (CeZrHfTiLa)O x (HEFO) as the support by a combination of mechanical milling with calcination at 900°C. Characterization results reveal that single Pd atoms are incorporated into HEFO (Pd 1 @HEFO) sublattice by forming stable Pd-O-M bonds (M = Ce/Zr/La). Compared to the traditional support stabilized catalysts such as Pd@CeO 2 , Pd 1 @HEFO affords the improved reducibility of lattice oxygen and the existence of stable Pd-O-M species, thus exhibiting not only higher low-temperature CO oxidation activity but also outstanding resistance to thermal and hydrothermal degradation. This work therefore exemplifies the superiority of high-entropy materials for the preparation of SACs.

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Section: Resultsmentioning

confidence: 99%

Entropy-stabilized single-atom Pd catalysts via high-entropy fluorite oxide supports

et al. 2020

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“…The reducibility of the CeO 2 shell support dramatically improves both catalytic performance and stability through the formation of strong metal–support interactions. ,, As such, we sought to better understand the role of support reducibility in promoting the stability of dispersed Pd species. To achieve this, we aged the Pd@CeO 2 catalyst, after forming halo sites through 800 °C air aging, in a completely reduced state, as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

Stabilizing Highly Dispersed Halo Sites in Thermally Restructured Palladium Core@Shell Nanoparticles for Improved Catalyst Activity and Durability

Hill

Bhat

Berquist

et al. 2021

ACS Appl. Nano Mater.

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Stabilizing high dispersions of catalytically active metals is integral to improving the lifetime, activity, and material utilization of catalysts that are periodically exposed to high temperatures during operation or maintenance. We have found that annealing palladium-based core@shell catalysts in air at elevated temperatures (800 °C) promotes the redispersion of active metals into highly dispersed sites, which we refer to as halo sites. Here, we examine the restructuring of Pd@SiO 2 and Pd@ CeO 2 core@shell catalysts over successive 800 °C aging cycles to understand the formation, activity, nanoscale structure, and stability of these palladium halo sites. While encapsulation generally improves metal utilization by providing a physical barrier that promotes redispersion over agglomeration, our cycled aging experiments demonstrate that halo sites are not stable in all catalysts. Halo sites continue to migrate in Pd@SiO 2 due to poor metal− support bonding, which leads to palladium agglomeration. In contrast, halo sites formed in Pd@CeO 2 remain stable. The dispersed palladium also synergistically stabilizes the ceria from agglomerating. We attribute this stability, in addition to an observed improvement in catalytic activity, to the coordination between palladium and reducible ceria that arises during the formation of halo sites. We probe the importance of ceria oxidation state on the stability of halo sites by aging Pd@CeO 2 after it has been reduced. While some halo sites agglomerate, we find that returning to air aging mitigates the loss of these sites and catalytic activity. Our findings illustrate how nanoscale catalyst structures can be designed to promote the formation of highly stable and dispersed metal sites.

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“…The reducibility of the CeO2 shell support dramatically improves both catalytic performance and stability through the formation of strong metal-support interactions. 24,49,60 As such, we sought to better understand the role of support reducibility in promoting the stability of dispersed Pd species. To achieve this, we aged the Pd@CeO2 catalyst, after forming halo sites through 800°C air aging, in a completely reduced state, as shown in Figure 5.…”

Section: Understanding the Role Of Support Reducibility In Halo Site Stabilitymentioning

confidence: 99%

Stabilizing Highly Dispersed Halo Sites in Thermally Restructured Palladium Core@shell Nanoparticles for Improved Catalyst Activity and Durability

Hill

Bhat

Berquist

et al. 2021

Preprint

View full text Add to dashboard Cite

Stabilizing high dispersions of catalytically active metals is integral to improving the lifetime, activity, and material utilization of catalysts that are periodically exposed to high temperatures during operation or maintenance. We have found that annealing palladium-based core@shell catalysts in air at elevated temperature (800°C) promotes the redispersion of active metal into highly dispersed sites, which we refer to as halo sites. Here, we examine the restructuring of Pd@SiO2 and Pd@CeO2 core@shell catalysts over successive 800°C aging cycles to understand the formation, activity, nanoscale structure and stability of these palladium halo sites. While encapsulation generally improves metal utilization by providing a physical barrier that promotes redispersion over agglomeration, our cycled aging experiments demonstrate that halo sites are not stable in all catalysts. Halo sites continue to migrate in Pd@SiO2 due to poor metal-support bonding, which leads to palladium agglomeration. In contrast, halo sites formed in Pd@CeO2 remain stable. The dispersed palladium also synergistically stabilizes the ceria from agglomerating. We attribute this stability, in addition to an observed improvement in catalytic activity, to the coordination between palladium and reducible ceria that arises during the formation of halo sites. We probe the importance of ceria oxidation state on the stability of halo sites by aging Pd@CeO2 after it has been reduced. While some halo sites agglomerate, we find that returning to air aging mitigates the loss of these sites and catalytic activity. Our findings illustrate how nanoscale catalyst structures can be designed to promote the formation of highly stable and dispersed metal sites.

show abstract

Thermally Induced Structural Evolution of Palladium‐Ceria Catalysts. Implication for CO Oxidation

Cited by 29 publications

References 90 publications

Entropy-stabilized single-atom Pd catalysts via high-entropy fluorite oxide supports

Entropy-stabilized single-atom Pd catalysts via high-entropy fluorite oxide supports

Stabilizing Highly Dispersed Halo Sites in Thermally Restructured Palladium Core@Shell Nanoparticles for Improved Catalyst Activity and Durability

Stabilizing Highly Dispersed Halo Sites in Thermally Restructured Palladium Core@shell Nanoparticles for Improved Catalyst Activity and Durability

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