Raspberry colloid-templated approach for the synthesis of palladium-based oxidation catalysts with enhanced hydrothermal stability and low-temperature activity

Shirman, Tanya; Toops, Todd J.; Shirman, Elijah; Shneidman, Anna V.; Liu, Sissi; Gurkin, Keeve; Alvarenga, Jack; Lewandowski, Michael; Aizenberg, Michael; Aizenberg, Joanna

doi:10.1016/j.cattod.2020.03.037

Cited by 17 publications

(36 citation statements)

References 38 publications

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“…[17][18][19] The partial nanoparticle embedding prevents sintering of the nanoparticles in the RCT catalysts at elevated temperatures and under reaction conditions. 18,20 Two dilute Pd in Au catalysts were prepared, one with 4 atm% Pd and one with 8 atm% Pd.…”

Section: Preparation Of the Dilute Alloy Nanoparticle Catalystsmentioning

confidence: 99%

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

et al. 2021

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Dilute Pd-in-Au alloy catalysts are promising materials for selective hydrogenation catalysis. Extensive surface science studies have contributed mechanistic insight on the energetic aspect of hydrogen dissociation, migration and recombination on dilute alloy systems. Yet, translating these fundamental concepts to the kinetics and free energy of hydrogen dissociation on nanoparticle catalysts operating at ambient pressures and temperatures remains challenging. Here, the effect of the Pd concentration and Pd ensemble size on the catalytic activity, apparent activation energy and rate limiting process is addressed by combining experiment and theory. Experiments in a flow reactor show that a compositional change from 4 to 8 atm% Pd of the Pd-in-Au alloy catalyst leads to strong increase in activity, even exceeding the activity per Pd atom of monometallic Pd under the same conditions, albeit with an increase in apparent activation energy. First-principles calculations show that the rate and apparent activation enthalpy for HD exchange increase when increasing the Pd ensemble size from single Pd atoms to Pd trimers in a Au surface, suggesting that the ensemble size distribution shifts from mainly single Pd atoms on the 4 atm% Pd alloy to larger Pd ensembles of at least three atoms for the 8 atm% Pd/Au catalyst. The DFT studies also indicated that the rate-controlling process is different: H 2 (D 2 ) dissociation determines the rate for single atoms whereas recombination of adsorbed H and D determines the rate on Pd trimers, similar to bulk Pd. 2Both experiment and theory suggest that the increased reaction rate with increasing Pd content and ensemble size stems from an entropic driving force. Finally, our results support hydrogen migration between Pd sites via Au and indicate that the dilute alloy design prevents the formation of subsurface hydrogen, which is crucial in achieving high selectivity in hydrogenation catalysis.

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Section: Preparation Of the Dilute Alloy Nanoparticle Catalystsmentioning

confidence: 99%

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

et al. 2021

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“…catalytic activity [16][17][18][19][20][21][22][23][24] and selectivity. [17,20,21,24] The material design consists of an ordered macroporous metal oxide framework with sub 10-nm metal NPs distributed at the pore walls.…”

Section: (2 Of 11)mentioning

confidence: 99%

“…[16,25] The robust, macroporous matrix allows facile mass transport throughout the catalyst. [26] The RCT approach therefore enables tailored design of oxidation [16][17][18][19]22,24] and hydrogenation [20,21,23] catalysts. So far, the potential of the RCTs for thermal catalysis has been demonstrated in selective alkyne hydrogenation, [20,21] HD exchange, [23] CO oxidation, [17,22] oxidative alcohol coupling, [17,24] and the oxidation of volatile organic compounds.…”

Section: (2 Of 11)mentioning

confidence: 99%

“…So far, the potential of the RCTs for thermal catalysis has been demonstrated in selective alkyne hydrogenation, [20,21] HD exchange, [23] CO oxidation, [17,22] oxidative alcohol coupling, [17,24] and the oxidation of volatile organic compounds. [18] A unique feature of the RCT catalysts is their excellent stability during catalysis [18][19][20]24] and thermal treatment, [18,19] allowing long catalyst lifetimes and facile reactivation via thermal treatment. [21] A particularly noteworthy finding by Shirman et al is the observation that not only the stability but also the activity of the RCT catalysts can be strongly enhanced compared to commercial catalysts, allowing drastic reductions in precious metal use and in energy cost in oxidation catalysis.…”

Section: (2 Of 11)mentioning

confidence: 99%

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On the Origin of Sinter‐Resistance and Catalyst Accessibility in Raspberry‐Colloid‐Templated Catalyst Design

Hoeven

Krämer

Dussi

et al. 2021

Adv Funct Materials

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Nanoparticle (NP) sintering is a major cause of the deactivation of supported catalysts. Raspberry-colloid-templated (RCT) catalysts are an emerging class of materials that show an unprecedented level of sinter-resistance and exhibit high catalytic activity. Here a comprehensive study of the origin of NP stability and accessibility in RCT catalysts using theoretical modeling, 3D electron microscopy, and epitaxial overgrowth is reported. The approach is showcased for silica-based RCT catalysts containing dilute Pd-in-Au NPs previously used in hydrogenation and oxidation catalysis. Modeling of the contact line of the silica precursor infiltrating into the assembled raspberry colloids suggests that a large part of the particles must be embedded into silica, which is confirmed by quantitative visualization of >200 individual NPs by dual-axis electron tomography. The RCT catalysts have a unique structure in which all NPs reside at the pore wall but have >50% of their surface embedded in the matrix, giving rise to the strongly enhanced thermal and mechanical stability. Importantly, epitaxial overgrowth of Ag on the supported NPs reveals that not only the NP surface exposed to the pore but the embedded interface as well remained chemically accessible. This mechanistic understanding provides valuable guidance in the design of stable catalytic materials.

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“…Shirman, Tanya; Toops, Todd J.; Shirman, Elijah [9] focused on tightening the regulations related to the treatment of vehicle exhaust gases, together with the continuous improvement of the engine design. This results in lower engine operating temperatures and inadvertently releases the overwhelming amount of pollutants during a cold start.…”

Section: Theorymentioning

confidence: 99%

Dependences of the warm-up time changes of catalytic converters in the open storage car conditions

2021

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In the article, emphasis made on determining the start operation time of catalytic converter in the open storage car conditions. In this regard, experiments made on author’s experimental setup, quantity of which provides a confidence probability 0,95. Results of experiments allow us to determine the dependences of the warm-up time changes of catalytic converters when the ambient temperature changes from +1°С to -30°С. The compliance with current regulatory requirements for content of CO and CH in engine exhaust provided.

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Raspberry colloid-templated approach for the synthesis of palladium-based oxidation catalysts with enhanced hydrothermal stability and low-temperature activity

Cited by 17 publications

References 38 publications

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

Entropic Control of HD Exchange Rates over Dilute Pd-in-Au Alloy Nanoparticle Catalysts

On the Origin of Sinter‐Resistance and Catalyst Accessibility in Raspberry‐Colloid‐Templated Catalyst Design

Dependences of the warm-up time changes of catalytic converters in the open storage car conditions

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