Controlling metal/oxide interactions in bifunctional nanostructured model catalysts: Pd and BaO on Al2O3/NiAl(110)

Desikusumastuti, Aine; Qin, Zhihui; Staudt, Thorsten; Happel, Markus; Lykhach, Yaroslava; Laurin, Mathias; Shaikhutdinov, Shamil K.; Libuda, Jörg

doi:10.1016/j.susc.2008.11.003

Cited by 21 publications

(48 citation statements)

References 34 publications

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“…21 For the deposition of smaller Ba particles (1 Å), we refer to the literature. 22 During deposition of Pd on the pristine Al 2 O 3 film, threedimensional crystallites, which preferentially nucleate at the rotational domain boundaries, are observed. The APD boundaries seem to be less attractive sites for the nucleation, and even fewer particles are found to nucleate on the terraces themselves.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Happel¹,

Desikusumastuti²,

Sobota³

et al. 2010

J. Phys. Chem. C

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Toward obtaining a more detailed understanding of the influence of SO x poisoning on the mechanism of NO x uptake on a NO x storage and reduction (NSR) catalyst, we have performed a model study under ultrahigh vacuum (UHV) conditions. A supported model catalyst based on a thin well-ordered alumina film grown on a NiAl(110) single crystal is used onto which BaO and Pd particles are deposited. Time-resolved (TR) infrared reflection absorption spectroscopy (IRAS) is applied to identify the species formed during NO 2 uptake on the catalyst surface, which has been pretreated with SO 2 . These results are compared to the NO 2 uptake on the corresponding fresh samples. It is shown that SO 2 readily decomposes upon adsorption on both the pristine Al 2 O 3 surface and the BaO and Pd loaded model systems. NO 2 reoxidizes the decomposition products to surface sulfites and sulfates. A pronounced influence of the SO 2 species on the interaction with NO 2 is observed leading to reduced NO 2 uptake and to a change of the preferential adsorption geometry from bridging to monodentate. A comparison of the integral intensity of the nitrate bands on the Ba-free and the Ba-containing samples furthermore suggests that SO 2 adsorbs preferentially on Ba 2+ centers rather than on the Al 3+ centers.

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Section: Resultsmentioning

confidence: 99%

“…The average particle diameter was calculated to be around 6 nm at a particle density around 1 × 10 12 cm -2 . 22 For deposition of Pd on the pristine support, the particles were stabilized by exposure to O 2 and CO at elevated temperature. More details about this procedure can be found in the literature.…”

Section: Resultsmentioning

confidence: 99%

Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Happel¹,

Desikusumastuti²,

Sobota³

et al. 2010

J. Phys. Chem. C

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“…[25,31,37] Herein, we focus on particles prestabilized by annealing in O 2 . [26,29] We assumed that these particles approached the stoichiometry of barium aluminate (BaAl 2 O 4 ) upon annealing.…”

Section: Resultsmentioning

confidence: 99%

“…From STM, we ascertained that the particle density was about 6 10 12 cm À2 , corresponding to an average of approximately 600 Ba 2 + ions in each particle. [25] Detailed discussions of the nucleation and growth behavior are in references [25] and [37].…”

Section: Resultsmentioning

confidence: 99%

Model NO_x Storage Materials at Realistic NO₂ Pressures

Desikusumastuti¹,

Schernich²,

Happel³

et al. 2009

ChemCatChem

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The interaction of NO2 with single‐crystal‐based model NOx storage materials, consisting of barium aluminate nanoparticles on Al2O3/NiAl(110), are investigated by time‐resolved infrared reflection absorption spectroscopy (TR‐IRAS) at realistic NO2 partial pressures up to 1.75 mbar. The data is compared to spectra obtained under ultrahigh vacuum (UHV) conditions on the same model system. At 300 K, the NO2 uptake at pressures around 1 mbar proceeds through rapid initial formation of surface nitrites and nitrates, similar to that under UHV conditions. The vibrational spectra of the surface species formed at realistic NO2 pressures are comparable to those for species formed under UHV conditions. Beyond the formation of surface species, the formation of bulk nitrates occurs, but is kinetically strongly hindered. At a very low rate, the formation of a disordered barium bulk nitrate is detected. At 500 K, this kinetic hindrance is overcome and the available Ba2+ is quantitatively converted to bulk Ba(NO3)2. The IRAS spectrum of these Ba(NO3)2 particles differs characteristically from those obtained for nitrate multilayers formed upon incomplete conversion under UHV conditions. In addition to the formation of bulk Ba(NO3)2, a more weakly bound disordered nitrate species is formed. This species gives rise to a dynamic NO2 uptake and release well below the decomposition temperature of bulk Ba(NO3)2. The experiments show that model studies under UHV conditions mainly provide information on the initial reaction mechanism, whereas the observation of actual bulk NOx storage phases requires experiments at realistic temperatures and pressures.

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“…Similar effects were previously observed for other metal/oxide systems (see, e.g., refs. [36][37][38]). A rough estimate of the particle size may be extracted from the STM images: an approximate Pt particle density of around (5.4 AE 1.0) 10 12 cm À2 was obtained.…”

Section: Morphology and Thermal Behavior Of Pt/ceo 2 /Cu(111)mentioning

confidence: 99%

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

et al. 2010

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Ceria-based supported noble-metal catalysts release oxygen, which may help to reduce the formation of carbonaceous residues, for example during hydrocarbon reforming. To gain insight into the microscopic origins of these effects, a model study is performed under ultrahigh-vacuum conditions using single-crystal-based supported model catalysts. The model systems are based on ordered CeO(2)(111) films on Cu(111), on which Pt nanoparticles are grown by physical vapor deposition. The growth and structure of the surfaces are characterized by means of scanning tunneling microscopy, and the electronic structure and reactivity are probed by X-ray photoelectron spectroscopy. Specifically, it is shown that the fully oxidized CeO(2) thin films undergo slight reduction upon Pt deposition (CeO(1.99)). This effect is enhanced upon annealing (CeO(1.96)), thus indicating facile oxygen release and reverse spillover. The model system is structurally stable up to temperatures exceeding 700 K. The activation of methane is investigated using high-kinetic-energy CH(4) (0.83 eV), generated by a supersonic molecular beam. It is shown that dehydrogenation occurs under rapid formation of CH or C species without detectable amounts of CH(3) being formed, even at low temperatures (100 K). The released hydrogen spills over to the CeO(2) support, which leads to the formation of OH groups. At 200 K and above, the OH groups start to decompose leaving additional Ce(3+) centers behind (CeO(1.97-1.94)). At up to 700 K, carbon deposits are quantitatively removed by reaction with oxygen, which is supplied by reverse spillover from the CeO(2) film, thus leading to substantial reduction of the support (approximately CeO(1.90-1.85)).

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Controlling metal/oxide interactions in bifunctional nanostructured model catalysts: Pd and BaO on Al2O3/NiAl(110)

Cited by 21 publications

References 34 publications

Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Model NO_x Storage Materials at Realistic NO₂ Pressures

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

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Controlling metal/oxide interactions in bifunctional nanostructured model catalysts: Pd and BaO on Al2O3/NiAl(110)

Cited by 21 publications

References 34 publications

Impact of Sulfur Poisoning on the NOxUptake of a NOxStorage and Reduction (NSR) Model Catalyst

Impact of Sulfur Poisoning on the NOxUptake of a NOxStorage and Reduction (NSR) Model Catalyst

Model NOx Storage Materials at Realistic NO2 Pressures

Microscopic Insights into Methane Activation and Related Processes on Pt/Ceria Model Catalysts

Contact Info

Product

Resources

About

Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Model NO_x Storage Materials at Realistic NO₂ Pressures