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- Adams, Emma, 1989, et al.
(author)
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Structure-function relationship for alumina supported platinum during formation of ammonia from nitrogen oxide and hydrogen in presence of oxygen
- 2016
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In: Physical Chemistry Chemical Physics. - 1463-9084 .- 1463-9076. ; 18:16, s. 10850-10855
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Journal article (peer-reviewed)abstract
- We study the structure-function relationship of alumina supported platinum during forma- tion of ammonia from nitrogen oxide and dihydrogen by employing in situ X-ray absorption and Fourier transformed infrared spectroscopy. Particular focus is directed towards the effect of increased levels of oxygen on the reaction as a model system for emerging technologies for passive selective catalytic reduction of nitrogen oxides. The suppressed formation of ammo- nia observed as the feed becomes net-oxidizing is accompanied by a considerable increase in the oxidation state of platinum as well as enhanced formation of surface nitrates and loss of NH-containing surface species. In the presence of (excess) oxygen, the ammonia formation is proposed to be limited by the weak interaction between nitrogen oxide and the oxidized platinum surface. This leads to slow dissociation rate of nitrogen oxide and thus low abun- dance of atomic nitrogen surface species that can react with adsorbed hydrogen atoms. In this case the consumption of hydrogen through the competing water formation reaction and decomposition/oxidation of ammonia are of less importance for the net ammonia formation.
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| 4. |
- Blomberg, Sara, et al.
(author)
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Strain Dependent Light-off Temperature in Catalysis Revealed by Planar Laser-Induced Fluorescence
- 2017
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 7:1, s. 110-114
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Journal article (peer-reviewed)abstract
- Understanding how specific atom sites on metal surfaces lower the energy barrier for chemical reactions is vital in catalysis. Studies on simplified model systems have shown that atoms arranged as steps on the surface play an important role in catalytic reactions, but a direct comparison of how the light-off temperature is affected by the atom orientation on the step has not yet been possible due to methodological constraints. Here we report in situ spatially resolved measurements of the CO2 production over a cylindrical-shaped Pd catalyst and show that the light-off temperature at different parts of the crystal depends on the step orientation of the two types of steps (named A and B). Our finding is supported by density functional theory calculations, revealing that the steps, in contrast to what has been previously reported in the literature, are not directly involved in the reaction onset but have the role of releasing stress.
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- Merte, Lindsay R., et al.
(author)
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Structure of two-dimensional Fe3O4
- 2020
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 152:11
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Journal article (peer-reviewed)abstract
- We have investigated the structure of an ultrathin iron oxide phase grown on Ag(100) using surface X-ray diffraction in combination with Hubbard-corrected density functional theory (DFT+U) calculations. The film exhibits a novel structure composed of one close-packed layer of octahedrally coordinated Fe2+ sandwiched between two close-packed layers of tetrahedrally coordinated Fe3+ and an overall stoichiometry of Fe3O4. As the structure is distinct from bulk iron oxide phases and the coupling with the silver substrate is weak, we propose that the phase should be classified as a metastable two-dimensional oxide. The chemical and physical properties are potentially interesting, thanks to the predicted charge ordering between atomic layers, and analogy with bulk ferrite spinels suggests the possibility of synthesis of a whole class of two-dimensional ternary oxides with varying electronic, optical, and chemical properties.
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- Shipilin, M., et al.
(author)
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Fe Oxides on Ag Surfaces : Structure and Reactivity
- 2017
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In: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 60:6-7
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Journal article (peer-reviewed)abstract
- One layer thick iron oxide films are attractive from both applied and fundamental science perspectives. The structural and chemical properties of these systems can be tuned by changing the substrate, making them promising materials for heterogeneous catalysis. In the present work, we investigate the structure of FeO(111) monolayer films grown on Ag(100) and Ag(111) substrates by means of microscopy and diffraction techniques and compare it with the structure of FeO(111) grown on other substrates reported in literature. We also study the NO adsorption properties of FeO(111)/Ag(100) and FeO(111)/Ag(111) systems utilizing different spectroscopic techniques. We discuss similarities and differences in the data obtained from adsorption experiments and compare it with previous results for FeO(111)/Pt(111).
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