Interaction of NO2 with Model NSR Catalysts: Metal–Oxide Interaction Controls Initial NOx Storage Mechanism

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

doi:10.1002/cphc.200800550

Cited by 19 publications

(26 citation statements)

References 73 publications

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“…[11][12][13][14] This system has been previously employed in a large number of model studies. 10,15,16 On this model support, the active metal particles are grown by physical vapor deposition (PVD), still under UHV conditions. Here, we use Pd nanoparticles on Al 2 O 3 / NiAl(110), a system which has been characterized in great detail with respect to its geometric and electronic structure, adsorption properties and reactivity.…”

Section: Introductionmentioning

confidence: 99%

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Sobota

Schmid

Happel

et al. 2010

Phys. Chem. Chem. Phys.

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Towards a better understanding of novel catalytic materials consisting of supported noble metal catalysts modified by an ionic liquid (IL) film, we have performed a study under ultrahigh-vacuum (UHV) conditions. The model surface consists of Pd nanoparticles grown in UHV on an ordered alumina film on NiAl(110). Thin films of the room temperature IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf(2)N] are deposited onto this surface by means of physical vapor deposition (PVD). The interaction of the IL with clean and CO-covered Pd/Al(2)O(3)/NiAl(110) at 300 K and the thermal behavior of the deposited IL films on Pd/Al(2)O(3)/NiAl(110) are investigated by time-resolved infrared reflection absorption spectroscopy (TR-IRAS) and X-ray photoelectron spectroscopy (XPS). At 300 K, the IL adsorbs molecularly both onto the Pd particles and onto the alumina. The IR spectra suggest that the [Tf(2)N](-) anions interact with Pd sites preferentially via the sulfonyl groups. CO pre-adsorbed on the Pd particles is partially displaced by the IL, even at 300 K, and only the part of CO adsorbed onto hollow sites on (111) facets of the Pd particles remains in place. Upon heating to temperatures higher than the desorption temperature of the IL (>400 K), molecular desorption of the IL competes with decomposition. The decomposition products, atomic species and small fragments, remain preferentially adsorbed onto the Pd nanoparticles and strongly modify their surface properties. Most of the decomposition products originate from the [BMIM](+) cations, whereas the [Tf(2)N](-) anions desorb for the most part.

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Section: Introductionmentioning

confidence: 99%

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Sobota

Schmid

Happel

et al. 2010

Phys. Chem. Chem. Phys.

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“…Features at around 1600 cm À1 and 1650 cm À1 have previously been assigned to surface nitrates on Al 3 + centers. [28,30] Such nitrate species on alumina may originate from areas between the BaAl 2 O 4 particles. In addition, there are other nitrogen-oxo species, [39] giving rise to bands in the same region.…”

Section: Reaction Behavior At Room Temperature and At No 2 Pressures mentioning

confidence: 99%

“…[16][17][18][19][20] More recently, the reaction of NO 2 with BaO deposits on Al 2 O 3 / NiAlA C H T U N G T R E N N U N G (110) were studied by Szanyi et al [21][22][23][24] and our group. [25][26][27][28][29][30][31] Some of the key results of these studies may be summarized as follows: A strong interaction with the support gave rise to interdiffusion of Al 3 + and Ba 2 + ions, resulting in the formation of barium aluminate-like nanoparticles. [29] As the exact stoichiometry was not established, we denoted these particles BaAl 2x O 1 + 3x .…”

Section: Introductionmentioning

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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“…In addition, the proposed mechanism for storage invokes a reversible surface spillover step of NO2 occurring between Pt and BaO sites. Therefore, to maintain a uniform distribution of Pt nanoparticles into the BaO matrix avoiding the sintering phenomenon is of crucial importance for achieving high rates of both NOx storage and its release [22]. A possible way to avoid Pt sintering is the control of the temperature, which should be maintained as low as possible (ideally lower than 600 °C), particularly when an oxidizing atmosphere is present [9].…”

Section: Resultsmentioning

confidence: 99%

Evaluating the NOx Storage Catalysts (NSC) Aging: A Preliminary Analytical Study with Electronic Microscopy

et al. 2017

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Featured Application: Could be aided to improve the efficiency of NSC catalysts and thus reduce the environmental impact of thermal-powered vehicles in accordance with the Paris agreement COP21.Abstract: This paper describes an expeditious and reliable method for determining the thermal effects in a static condition of commercial NOx storage catalysts (NSCs) using scanning electron microscopy with an energy dispersive X-ray analytical system (SEM/EDS). It is worth remarking that possible changes in the morphology and in the elemental composition of the catalyst may be considered as the most important causes of the lower conversion of NOx. The information attained in this work indicates that Pt nanoparticle sintering is strongly increased by the oxygen exposure, and this can be considered a very useful preliminary investigation for the studies already present in the literature on the efficiency of NSCs.

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Interaction of NO₂ with Model NSR Catalysts: Metal–Oxide Interaction Controls Initial NO_x Storage Mechanism

Cited by 19 publications

References 73 publications

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Model NO_x Storage Materials at Realistic NO₂ Pressures

Evaluating the NOx Storage Catalysts (NSC) Aging: A Preliminary Analytical Study with Electronic Microscopy

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Interaction of NO2 with Model NSR Catalysts: Metal–Oxide Interaction Controls Initial NOx Storage Mechanism

Cited by 19 publications

References 73 publications

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Ionic liquid based model catalysis: interaction of [BMIM][Tf2N] with Pd nanoparticles supported on an ordered alumina film

Model NOx Storage Materials at Realistic NO2 Pressures

Evaluating the NOx Storage Catalysts (NSC) Aging: A Preliminary Analytical Study with Electronic Microscopy

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Interaction of NO₂ with Model NSR Catalysts: Metal–Oxide Interaction Controls Initial NO_x Storage Mechanism

Model NO_x Storage Materials at Realistic NO₂ Pressures