| 1. |
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| 2. |
- Archfield, Stacey A., et al.
(författare)
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Accelerating advances in continental domain hydrologic modeling
- 2015
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 51:12, s. 10078-10091
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Tidskriftsartikel (refereegranskat)abstract
- In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.
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| 3. |
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| 4. |
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| 5. |
- Goriachko, A., et al.
(författare)
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Hexagonal C and BN superstructures on Ru(0001) and Ge(111)
- 2013
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Ingår i: Materialwissenschaft und Werkstofftechnik. - : Wiley. - 0933-5137. ; 44:2-3, s. 129-135
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Tidskriftsartikel (refereegranskat)abstract
- A brief overview of hexagonal superstructures with a periodicity of similar to 3 nm formed on Ru(0001) and Ge(111) by graphene or hexagonal boron nitride with a thickness of just a single atomic layer is given. A periodic height corrugation of such layers due to the lattice mismatch with the substrate material is of the order of 0.1 nm. Selected examples of scanning tunneling microscopy (STM) and low energy electron microscopy/diffraction (LEEM/LEED) investigations of BN/Ru(0001), C/Ru(0001), (BN)(x)C-y/Ru(0001) and C/Ge(111) are presented. These systems can act as nanotemplates for metal nanoparticles growth, as well as strongly heterogeneous substrates for molecular adsorption.
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| 6. |
- Goriachko, A., et al.
(författare)
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Oxygen-etching of h-BN/Ru(0001) nanomesh on the nano- and mesoscopic scale
- 2008
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:28, s. 10423-10427
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the recently discovered b-BN/Ru(0001) nanomesh is of crucial importance for potential applications as a nanotemplate. In particular, thermal stability in oxygen environment is important for nanocatalysis applications. We report here on the etching experiments of the h-BN layer by molecular oxygen exposure at elevated temperatures. This process is studied both by scanning tunneling microscopy (STM) on a microscopic scale and with in situ low energy electron microscopy (LEEM) on the mesoscopic scale. Temperature thresholds are determined for the microscopic (600 degrees C) and the mesoscopic (750 degrees C) etching processes for O-2 pressures up to 1 x 10(-6) mbar. Submonolayer amounts of An deposited on the h-BN/Ru(0001) nanomesh improve considerably the stability of the h-BN nanomesh against etching by O-2.
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| 7. |
- He, YB, et al.
(författare)
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Ru(0001) model catalyst under oxidizing and reducing reaction conditions: in-situ high-pressure surface X-ray diffraction study
- 2005
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 109:46, s. 21825-21830
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Tidskriftsartikel (refereegranskat)abstract
- With surface X-ray diffraction (SXRD) using a high-pressure reaction chamber we investigated in-situ the oxidation of the Ru(0001) model catalyst under various reaction conditions, starting from a strongly oxidizing environment to reaction conditions typical for CO oxidation. With a mixture Of O-2 and CO (stoichiometry, 2:1) the partial pressure of oxygen has to be increased to 20 mbar to form the catalytically active RuO2(110) oxide film, while in pure oxygen environment a pressure of 10(-5) mbar is already sufficient to oxidize the Ru(0001) surface. For preparation temperatures in the range of 550-630 K a self-limiting RUO2(110) film is produced with a thickness of 1.6 nm. The RuO2(110) film grows self-acceleratedly after an induction period. The RuO2 films on Ru(0001) can readily be reduced by H-2 and CO exposures at 415 K, without an induction period.
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| 8. |
- Knapp, M., et al.
(författare)
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Complex interaction of hydrogen with the RuO2(110) surface
- 2007
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:14, s. 5363-5373
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Tidskriftsartikel (refereegranskat)abstract
- Using a variety of dedicated surface sensitive techniques, we studied the interaction of hydrogen with bare and adsorbate modified RuO2(110) surfaces on the atomic scale. Hydrogen interacts strongly with the undercoordinated O atoms, thereby forming hydroxyl groups and passivating available oxygen species on the oxide surface, for instance, for the catalytic CO oxidation reaction. Temperature programmed reaction and desorption elucidate the complex reaction behavior of hydrogen with O precovered RuO2(110), including the hydrogen transfer reaction between the different kinds of undercoordinated surface oxygen atoms. Hydroxyl, water species, and hydrogen transfer are identified with high-resolution O1s core level spectroscopy by comparison with density functional theory (DFT) calculated O1s core level shifts. DFT calculations provide adsorption energies, atomic geometries, as well as diffusion barriers of H atoms on the RuO2(110) surface.
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| 9. |
- Knapp, M., et al.
(författare)
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Unusual process of water formation on RuO2(110) by hydrogen exposure at room temperature
- 2006
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 110:29, s. 14007-14010
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Tidskriftsartikel (refereegranskat)abstract
- The reduction mechanism of the RuO2(110) surface by molecular hydrogen exposure is unraveled to an unprecedented level by a combination of temperature programmed reaction, scanning tunneling microscopy, high-resolution core level shift spectroscopy, and density functional theory calculations. We demonstrate that even at room temperature hydrogen exposure to the RuO2(110) surface leads to the formation of water. In a two-step process, hydrogen saturates first the bridging oxygen atoms to form (O-br-H) species and subsequently part of these O-br-H groups move to the undercoordinated Ru atoms where they form adsorbed water. This latter process is driven by thermodynamics leaving vacancies in the bridging O rows.
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| 10. |
- Over, H., et al.
(författare)
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Direct comparison of the reactivity of the non-oxidic phase of Ru(0001) and the RuO2 phase in the Co oxidation reaction
- 2009
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 603:2, s. 298-303
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Tidskriftsartikel (refereegranskat)abstract
- Applying in situ surface X-ray diffraction (SXRD) together with on-line mass spectrometry during the CO oxidation over Ru(0001) allows a direct comparison of the reactivity of the non-oxidic state with that of the RuO2(110) covered surface. This comparison reveals that the RuO2(110) surface is a catalytically active phase at least as active as the non-oxidic phase. At high CO and O-2 pressures of 200 mbar and temperatures above 550 K, the CO oxidation reaction does not proceed isothermally on the RuO2(110) surface. The released reaction heat leads rather to an increase of the sample temperature of up to 130 K accompanied by a self-acceleration of the CO oxidation reaction. (C) 2008 Elsevier B.V. All rights reserved.
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| 11. |
- Over, H, et al.
(författare)
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Experimental and simulated STM images of stoichiometric and partially reduced RuO2(110) surfaces including adsorbates
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 515:1, s. 143-156
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental and DFT-simulated STM images of ultrathin RuO2(110) films on Ru(0001), including adsorbates such as oxygen and CO. We are able to identify the under-coordinated O atoms on the RuO2(110) surface with STM, i.e. the bridging O atoms and the on-top O atoms. The partial reduction of the RuO2(110) surface by CO exposure at room temperature leads to a surface where part of the bridging O atoms have been removed and some of the vacancies are occupied by bridging CO. When dosing 10 L of CO at room temperature, the RuO2(110) surface becomes fully mildly reduced in that all bridging 0 atoms are replaced by bridging CO molecules. Annealing the surface to 600 K produces holes on the terraces of such a mildly reduced RuO2(110) surface. These pits are not generated by the recombination of lattice O with CO, but rather these pits are assigned to a complex temperature-induced rearrangement of surface atoms in the topmost RuO2 double layer of RuO2(110). With this process the bridging O atoms are again populated and surplus Ru atoms agglomerate in small islands at the rims of the holes. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 12. |
- Over, H., et al.
(författare)
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In situ structure-activity correlation experiments of the ruthenium catalyzed CO oxidation reaction
- 2009
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 145:3-4, s. 236-242
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Konferensbidrag (refereegranskat)abstract
- The complex structure-activity correlation of the CO oxidation on ruthenium has been studied in a batch reactor by using in situ surface X-ray diffraction (SXRD) and on-line mass spectrometry. Two distinct active phases are identified at higher pressures in the mbar range depending on the reaction conditions: a non-oxidic phase and a RuO2(1 1 0) layer of variable thickness ranging from 1.5 nm to 10 nm. For reaction temperatures lower than 520 K the experimental turnover frequency (TOF) numbers are shown to be almost identical for the two types of active phases. Above 520 K the RuO2(1 1 0) layer turned out to be much more active than the non-oxidic phase. Kinetic reaction experiments on the RuO2(1 1 0) phase reveal an activation energy of 78 +/- 10 kJ/mol which is in perfect agreement with corresponding reactivity experiments on supported and powder RuO2 catalyst. Under oxidizing reaction conditions and high concentration of CO2 in the gas mixture, the RuO2(1 1 0) model catalyst shows reversible product-poisoning. (C) 2008 Elsevier B.V. All rights reserved.
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| 13. |
- Over, H, et al.
(författare)
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On the origin of the Ru-3d(5/2) satellite feature from RuO2(110)
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 504:1-3, s. 196-200
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Tidskriftsartikel (refereegranskat)abstract
- High resolution core level spectroscopy in combination with density functional theory calculations are used to study the satellite feature of the Ru-3d(5/2), core level spectrum whose interpretation is still a matter of debate. We present evidence that the satellite peak is not related to any structural properties of the RuO2(1 1 0) surface. The binding energy shift between the Ru-3d(5/2) component and the satellite peak is close to the electron energy loss due to plasmon excitation. We propose therefore that the satellite peak is due to excitation of the RuO2 plasmon. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 14. |
- Over, H, et al.
(författare)
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Visualization of atomic processes on ruthenium dioxide using scanning tunneling microscopy
- 2004
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 5:2, s. 167-174
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Forskningsöversikt (refereegranskat)abstract
- The visualization of surface reactions on the atomic scale provides direct insight into the microscopic reaction steps taking place in a catalytic reaction at a (model) catalyst's surface. Employing the technique of scanning tunneling microscopy (STM), we investigated the CO oxidation reaction over the RuO2(110) and RuO2(100) surfaces. For both surfaces the protruding bridging O atoms are imaged in STM as bright features. The reaction mechanism is identical on both orientations of RuO2. CO molecules adsorb on the undercoordinated surface Ru atoms from where they recombine with undercoordinated O atoms to form CO2 at the oxide surface. In contrast to the RuO2(110) surface, the RuO2(100) surface stabilizes also a catalytically inactive c(2 x 2) phase may play an important role in the deactivation of RuO2 catalysts in the electrochemical Cl-2 evolution and other heterogeneous reactions.
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| 15. |
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| 16. |
- Seitsonen, A. P., et al.
(författare)
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Reaction mechanism of ammonia oxidation over RuO2(110): A combined theory/experiment approach
- 2009
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 603:18, s. 113-116
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Tidskriftsartikel (refereegranskat)abstract
- Combining state-of-the-art density functional theory (DFT) calculations with high resolution core level shift spectroscopy experiments we explored the reaction mechanism of the ammonia oxidation reaction over RuO2(1 1 0). The high catalytic activity of RuO2(1 1 0) is traced to the low activation energies for the successive hydrogen abstractions of ammonia by on-top O (less than 73 kJ/mol) and the low activation barrier for the recombination of adsorbed O and N (77 kJ/mol) to form adsorbed NO. The NO desorption is activated by 121 kJ/mol and represents therefore the rate determining step in the ammonia oxidation reaction over RuO2 (1 1 0). (C) 2009 Elsevier B.V. All rights reserved.
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| 17. |
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| 18. |
- Weber, Tim, et al.
(författare)
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Potential-Induced Pitting Corrosion of an IrO2(110)-RuO2(110)/Ru(0001) Model Electrode under Oxygen Evolution Reaction Conditions
- 2019
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 9:7, s. 6530-6539
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Tidskriftsartikel (refereegranskat)abstract
- Sophisticated IrO2(110)-based model electrodes are prepared by deposition of a 10 nm thick single-crystalline IrO2(110) layer supported on a structure-directing RuO2(110)/Ru(0001) template, exposing a regular array of mesoscopic rooflike structures. With this model electrode together with the dedicated in situ synchrotron based techniques (SXRD, XRR) and ex situ characterization techniques (SEM, ToF-SIMS, XPS), the corrosion process of IrO2(110) in an acidic environment (pH 0.4) is studied on different length scales. Potential-induced pitting corrosion starts at 1.48 V vs SHE and is initiated at so-called surface grain boundaries, where three rotational domains of IrO2(110) meet. The most surprising result is, however, that even when the electrode potential is increased to 1.94 V vs SHE 60-70% of the IrO2 film still stays intact down to the mesoscale and atomic scale and no uniform thinning of the IrO2(110) layer is encountered. Neither flat IrO2(110) terraces nor single steps are attacked. Ultrathin single-crystalline IrO2(110) layers seem to be much more stable to anodic corrosion than hitherto expected.
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| 19. |
- Zweidinger, S., et al.
(författare)
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In situ studies of the oxidation of HCl over RuO2 model catalysts: Stability and reactivity
- 2010
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 1090-2694 .- 0021-9517. ; 272:1, s. 169-175
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Tidskriftsartikel (refereegranskat)abstract
- Structure-activity experiments were performed for the HCl oxidation reaction (Deacon-like process) over RuO2 model catalysts - RuO2(1 1 0) and RuO2(1 0 0) - applying in situ surface X-ray diffraction (SXRD) combined with on-line mass spectrometry. The studied model catalysts turned out to be long-term stable under reaction conditions with gas feed ratios p(HCl):p(O-2) ranging from 1:4 to 4:1 in the mbar pressure regime and temperatures as high as 685 K. Even pure HCl exposure in the mbar regime was not able to reduce RuO2 below 600 K; above 650 K chemical reduction of the oxide sets in. Under strongly oxidizing reaction conditions, the (surface) oxides grow slowly in thickness. On-line reactivity experiments of both types of model catalysts in a batch reactor yield a mean turn-over frequency (TOP) of 0.6 Cl-2 molecules per second and active site for the HCl oxidation at 650 K and initial partial pressures of p(HCl) = 2 mbar and p(O-2) = 0.5 mbar. The HCl oxidation over RuO2 is therefore considered to be structure insensitive. (C) 2010 Elsevier Inc. All rights reserved.
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| 20. |
- Zweidinger, S., et al.
(författare)
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Reaction mechanism of the oxidation of HCl over RuO2(110)
- 2008
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:27, s. 9966-9969
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution core-level shift spectroscopy and temperature-programmed reaction experiments together with density functional theory calculations reveal that the oxidation of HCl with oxygen producing Cl-2 and water proceeds on the chlorine-stabilized RuO2(110)surface via a one-dimensional Langmuir-Hinshelwood mechanism. The recombination of two adjacent chlorine atoms on the catalyst's surface constitutes the rate-determining step in this novel Deacon-like process.
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