Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

Cheng, Lei; Ge, Qingfeng

doi:10.1016/j.susc.2007.04.112

Cited by 22 publications

(25 citation statements)

References 24 publications

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“…The stability of these surface species is expected to depend critically on the underlying support. For monodisperse BaO n clusters, the interaction with the Al 2 O 3 support was recently suggested to have a stabilizing influence on NO 2 adsorption [37]. Indeed, activating an enhanced interaction with the Al 2 O 3 by pre-annealing the (BaO) *30 /Al 2 O 3 leads to a slight increase of the decomposition temperature (see Fig.…”

mentioning

confidence: 96%

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

et al. 2007

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Based on a well-defined model-catalyst approach, we study the particle size dependent properties of NO x storage materials. The single-crystal based model systems are prepared on an ordered Al 2 O 3 film, on which BaO nanoparticles are grown under ultrahigh-vacuum (UVH) conditions. Particle size and density are characterized by scanning tunneling microscopy (STM). The interaction with NO 2 is probed by molecular beam (MB) methods in combination with time-resolved IR reflection absorption spectroscopy (TR-IRAS). It is found that both, the stability and the formation kinetics of alumina supported barium nitrate nanoparticles show a strong dependence on particle size. Very small BaO particles are rapidly converted into nitrates, however, the resulting aggregates exhibit a strongly reduced thermal stability. Surface and bulk nitrate and nitrate features are identified by means of vibrational spectroscopy. It is concluded that the size dependencies are related to the formation and decomposition of surface-related BaNO x species the decomposition temperature of which can be tuned over an exceptionally large temperature interval. It is suggested that the stability of these surface NO x species is strongly modified by the underlying support.

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confidence: 96%

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

et al. 2007

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“…Among all of the steps involved in the NSR catalytic processes, NO x storage on BaO has attracted a great deal of attention in terms of experimental and theoretical studies. [1][2][3][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Therefore, it is imperative to understand the stability and reactivity of BaO prior to considering it as the main NO x storage component in NSR catalysts.…”

mentioning

confidence: 99%

“…However, the fundamental scientific issues associated with BaO on other support oxides are not well understood. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Furthermore, growing BaO on cerium oxide (CeO 2 ) and yttria-stabilized zirconia (YSZ) has advantages. Functional oxides such as CeO 2 and YSZ have strong abilities in oxygen storage and release.…”

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confidence: 99%

Growth and Characterization of Barium Oxide Nanoclusters on YSZ(111)

et al. 2009

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Barium oxide (BaO) was grown on a yttria-stabilized zirconia (YSZ) substrate by oxygen plasma-assisted molecular beam epitaxy. In situ reflection high-energy electron diffraction, ex situ X-ray diffraction (XRD), atomic force microscopy, and X-ray photoelectron spectroscopy (XPS) have confirmed that BaO grows as clusters on YSZ(111). During and following growth under ultrahigh vacuum conditions, we found BaO remained in single phase. When exposed to ambient conditions, the clusters transformed to BaCO 3 and/or Ba(OH) 2 H 2 O. However, in a few attempts of BaO growth, XRD results show a fairly single-phase cubic BaO with a lattice constant of 0.5418(1) nm. XPS results show that exposing BaO clusters to ambient conditions resulted in the formation of BaCO 3 on the surface and partly Ba(OH) 2 throughout the bulk. On the basis of the observations, it is concluded that the BaO nanoclusters grown on YSZ(111) are highly reactive in ambient conditions.

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“…This can be attributed to a synergistic effect between the g-Al 2 O 3 (100) substrate and the supported AEOs as has been identified in a previous study of NO 2 adsorption on g-Al 2 O 3 -supported BaO clusters. 21 In the previous work, Cheng and Ge indicated that the interfacial area between the g-Al 2 O 3 and the monodispersed BaO clusters provided optimal sites for NO 2 adsorption. 21 Unlike the adsorption of NO 2 + NO 3 pairs on AEO(001) surfaces discussed above, we find that the adsorption energies for the adsorbed NO 2 + NO 3 pairs in each structure on the different monomeric AEOs/g-Al 2 O 3 (100) surfaces are essentially the same.…”

Section: Monomeric Aeos On the C-al 2 O 3 (100) Surfacementioning

confidence: 95%

“…20 Recently, Cheng and Ge studied NO 2 adsorption on g-Al 2 O 3 -supported BaO clusters. 21,22 They found a strong synergistic effect between the supported (BaO) 2 clusters and the g-Al 2 O 3 substrate on the NO 2 adsorption. Despite these efforts, detailed structures of the two proposed (''surface'' and ''bulk'') nitrate species over BaO/g-Al 2 O 3 are still not clear.…”

Section: Introductionmentioning

confidence: 99%

Characterization of surface and bulk nitrates of γ-Al2O3–supported alkaline earth oxides using density functional theory

Mei

Kwak

et al. 2009

Phys. Chem. Chem. Phys.

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"Surface" and "bulk" nitrates formed on a series of alkaline earth oxides (AEOs), AE(NO3)2, were investigated using first-principles density functional theory calculations. The formation of these surface and bulk nitrates was modeled by the adsorption of NO2+NO3 pairs on gamma-Al2O3-supported monomeric AEOs (MgO, CaO, SrO, and BaO) and on the extended AEO(001) surfaces, respectively. The calculated vibrational frequencies of the surface and bulk nitrates based on our proposed models are in good agreement with experimental measurements of AEO/gamma-Al2O3 materials after prolonged NO2 exposure. This indicates that experimentally observed "surface" nitrates are most likely formed with isolated two-dimensional (including monomeric) AEO clusters on the gamma-Al2O3 substrate, while the "bulk" nitrates are formed on exposed (including (001)) surfaces (and likely in the bulk as well) of large three-dimensional AEO particles supported on the gamma-Al2O3 substrate. Also in line with the experiments, our calculations show that the low and high frequency components of the vibrations for both surface and bulk nitrates are systematically red-shifted with the increasing basicity and cationic size of the AEOs. The adsorption strengths of NO2+NO3 pairs are nearly the same for the series of alumina-supported monomeric AEOs, while the adsorption strengths of NO2+NO3 pairs on the AEO surfaces increase in the order of MgO

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Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

Cited by 22 publications

References 24 publications

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

Growth and Characterization of Barium Oxide Nanoclusters on YSZ(111)

Characterization of surface and bulk nitrates of γ-Al2O3–supported alkaline earth oxides using density functional theory

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