CO Oxidation and Site Speciation for Alloyed Palladium–Platinum Model Catalysts Studied by <i>in Situ</i> FTIR Spectroscopy

Martin, Natalia; Skoglundh, Magnus; Smedler, Gudmund; Raj, Agnes; Thompsett, David; Velin, Peter; Martínez-Casado, Francisco J.; Matěj, Zdeněk; Balmès, Olivier; Carlsson, Per-Anders

doi:10.1021/acs.jpcc.7b07611

Cited by 14 publications

(13 citation statements)

References 43 publications

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“…With the common assumption of similar extinction coefficients for the different CO species, the relative presence of the different CO species can be determined. For the catalysts with high dispersion, the bar graph in Figure c shows that a significant amount of bridge and 3-fold hollow bonded CO species occupies the Pd sites in line with previous results, giving rise to a stoichiometric factor (SF) of 2.2 Pd atoms per CO molecule. For Pd/γ-Al 2 O 3 -900 with larger Pd particles, some spectral differences are seen.…”

Section: Resultssupporting

confidence: 89%

Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts

Velin

Skoglundh

et al. 2019

J. Phys. Chem. C

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In situ diffuse reflectance infrared Fourier transform spectroscopy has been used to distinguish surface hydroxyl groups on Al 2 O 3 and PdO/Al 2 O 3 model catalysts calcined at 500−900 °C. Employing the operando approach, the formation of surface hydroxyl groups has been correlated to the methane oxidation activity for PdO/Al 2 O 3 catalysts using a PdO powder sample as reference. The results show that the alumina support stabilizes active PdO particles leading to enhanced apparent methane turnover frequency (TOF), which decreases slowly in dry conditions due to alumina hydroxylation. Wet conditions cause severe hydroxylation that is detrimental for the methane TOF. The hydroxylation follows two different routes, i.e., spillover of hydrogen-containing species to the PdO-Al 2 O 3 boundary and/or the close proximity of the supported PdO particles and under wet conditions also dissociation of gas phase water on the entire alumina surface. Both hydroxylation routes obey varying kinetics such that near saturation is reached quickly (minutes) followed by a continuous slow growth for prolonged exposure times (hours). At low temperatures, inhibition of palladium active sites on the rim of the PdO particles close to alumina seems to be of particular importance for the observed detrimental effect of water, whereas water induced morphological changes (no sintering observed) of the PdO particles play a minor role.

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Section: Resultssupporting

confidence: 89%

Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts

Velin

Skoglundh

et al. 2019

J. Phys. Chem. C

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“…Adsorption of CO on palladium (and noble metals in general) often results in a variety of adsorption configurations including linearly bound and different types of bridge-bonded CO species. 47 Their relative presence depends on the palladium particle morphology. This is commonly accounted for by inferring a stoichiometric factor (F S ) correlating the number surface palladium atoms probed by one CO molecule.…”

Section: Catalysis Science and Technology Papermentioning

confidence: 99%

Palladium dispersion effects on wet methane oxidation kinetics

Velin

Florén

Skoglundh

et al. 2020

Catal. Sci. Technol.

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“…For catalytic oxidation of both CO and CH 4 , palladium is often the element of choice when designing the active component of the catalyst. − Under oxidizing conditions at low temperatures, Pd-based catalysts typically undergo oxidation such that PdO develops, which becomes the active component in practice. − For ideal single crystals, it has been shown that a thin layer of PdO(101) can form on the PdO(100) surface when exposed to oxygen. The PdO(101) surface exposes under-coordinated Pd atoms that excel the catalytic activity for both CO , and CH 4 oxidation. , If the PdO layer grows too thick, a nonepitaxial growth takes over such that a polycrystalline PdO develops, which has a low catalytic activity .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Catalytically Active Au Core─Pd Shell Nanoparticles Supported on Alumina

et al. 2022

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A two-step seeded-growth method was refined to synthesize Au@Pd core@shell nanoparticles with thin Pd shells, which were then deposited onto alumina to obtain a supported Au@Pd/Al2O3 catalyst active for prototypical CO oxidation. By the strict control of temperature and Pd/Au molar ratio and the use of l-ascorbic acid for making both Au cores and Pd shells, a 1.5 nm Pd layer is formed around the Au core, as evidenced by transmission electron microscopy and energy-dispersive spectroscopy. The core@shell structure and the Pd shell remain intact upon deposition onto alumina and after being used for CO oxidation, as revealed by additional X-ray diffraction and X-ray photoemission spectroscopy before and after the reaction. The Pd shell surface was characterized with in situ infrared (IR) spectroscopy using CO as a chemical probe during CO adsorption–desorption. The IR bands for CO ad-species on the Pd shell suggest that the shell exposes mostly low-index surfaces, likely Pd(111) as the majority facet. Generally, the IR bands are blue-shifted as compared to conventional Pd/alumina catalysts, which may be due to the different support materials for Pd, Au versus Al2O3, and/or less strain of the Pd shell. Frequencies obtained from density functional calculations suggest the latter to be significant. Further, the catalytic CO oxidation ignition-extinction processes were followed by in situ IR, which shows the common CO poisoning and kinetic behavior associated with competitive adsorption of CO and O2 that is typically observed for noble metal catalysts.

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CO Oxidation and Site Speciation for Alloyed Palladium–Platinum Model Catalysts Studied by in Situ FTIR Spectroscopy

Cited by 14 publications

References 43 publications

Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts

Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts

Palladium dispersion effects on wet methane oxidation kinetics

Synthesis and Characterization of Catalytically Active Au Core─Pd Shell Nanoparticles Supported on Alumina

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