Water inhibition and role of palladium adatoms on Pd/Al2O3 catalysts during methane oxidation

Boucly, Anthony; Artiglia, Luca; Roger, Maneka; Zabilskiy, Maxim; Beck, Arik; Ferri, Davide; Bokhoven, Jeroen A. van

doi:10.1016/j.apsusc.2022.154927

Cited by 15 publications

(22 citation statements)

References 62 publications

(105 reference statements)

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“…Pd 3d photoemission spectra of as-synthesized and aged Pd/Al 2 O 3 , co-impregnated Pd/Pt/Al 2 O 3 catalyst, and the physical mixture Pd/Al 2 O 3 + Pt/Al 2 O 3 catalysts showed a complex pattern containing contributions from multiple species (Figure i–k). The signal was deconvoluted into four components that were attributed to metallic, surface oxide, bulk oxide, and highly cationic Pd species. , This latter species is commonly observed in low loading catalysts and has been attributed to Pd atoms strongly interacting with the support. , In the Pd/Al 2 O 3 catalyst, only oxidized Pd species were detected in both fresh and aged samples (Figure i). In contrast, signals related to all the Pd species were found even in the initial co-impregnated catalyst (Figure j).…”

Section: Resultsmentioning

confidence: 99%

“…The signal was deconvoluted into four components that were attributed to metallic, surface oxide, bulk oxide, and highly cationic Pd species. 24,25 This latter species is commonly observed in low loading catalysts and has been attributed to Pd atoms strongly interacting with the support. 2,25 In the Pd/ Al 2 O 3 catalyst, only oxidized Pd species were detected in both fresh and aged samples (Figure 5i).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…24,25 This latter species is commonly observed in low loading catalysts and has been attributed to Pd atoms strongly interacting with the support. 2,25 In the Pd/ Al 2 O 3 catalyst, only oxidized Pd species were detected in both fresh and aged samples (Figure 5i). In contrast, signals related to all the Pd species were found even in the initial coimpregnated catalyst (Figure 5j).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The spin–orbit splitting of Pd 3d was set to 5.3 eV. The fitting parameters used (peaks positions, shape and full width at half maximum) are based on previous reports obtained on palladium foil and supported palladium nanoparticles. , …”

Section: Experimental Sectionmentioning

confidence: 99%

“…The fitting parameters used (peaks positions, shape and full width at half maximum) are based on previous reports obtained on palladium foil and supported palladium nanoparticles. 24,25 X-ray fluorescence data was collected using a Spectro Xepos HE XRF spectrometer. The spectrometer is equipped with a solid-state detector (SSD), and samples are run at four different energies.…”

Section: ■ Introductionmentioning

confidence: 99%

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Colloidally Engineered Pd and Pt Catalysts Distinguish Surface- and Vapor-Mediated Deactivation Mechanisms

Beck

Goodman

et al. 2023

ACS Catal.

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Noble metal-based catalysts are ubiquitous because of their high activity and stability. However, they irreversibly deteriorate over time especially in high-temperature applications. In these conditions, sintering is the main reason for deactivation, and understanding how sintering occurs gives the opportunity to mitigate these detrimental processes. Previous studies successfully distinguished between two fundamental sintering modes, namely, particle migration and coalescence (PMC) and Ostwald ripening (OR). However, differentiation between surface- and vapor-mediated Ostwald ripening processes has not been demonstrated yet, even though it is crucial information to tune metal/support interactions and stabilize catalysts. Here, we demonstrate that surface- and vapor-mediated ripening occur in two distinct regimes of temperature with some overlap using Pt and Pd catalysts prepared from colloidal nanocrystals as precursors. By either co-impregnating the two metal nanocrystals on the same grain of alumina support or by physically mixing powders of the two distinct metal catalysts, we tune the intermetal particle distance between nanometers and micrometers. We then use methane complete oxidation as a reporter reaction that occurs at higher rates on pure Pd and lower rates on alloyed Pd/Pt catalysts to trace the movement of Pt in the system. Aging the catalysts at different temperatures allows us to reveal that Pt initially sinters by surface-mediated ripening until ∼750 °C, but at temperatures above 800 °C, vapor-mediated ripening by PtO2 becomes the main sintering mechanism. This work demonstrates how colloidal catalysts allow unique insights into the working and deactivation mechanisms of supported systems.

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