Institute for Storage Ring Facilities

Århus, Denmark

Institute for Storage Ring Facilities

Århus, Denmark
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Fester J.,University of Aarhus | Garcia-Melchor M.,SLAC | Garcia-Melchor M.,Trinity College Dublin | Walton A.S.,University of Manchester | And 5 more authors.
Nature Communications | Year: 2017

Transition metal oxides show great promise as Earth-abundant catalysts for the oxygen evolution reaction in electrochemical water splitting. However, progress in the development of highly active oxide nanostructures is hampered by a lack of knowledge of the location and nature of the active sites. Here we show, through atom-resolved scanning tunnelling microscopy, X-ray spectroscopy and computational modelling, how hydroxyls form from water dissociation at under coordinated cobalt edge sites of cobalt oxide nanoislands. Surprisingly, we find that an additional water molecule acts to promote all the elementary steps of the dissociation process and subsequent hydrogen migration, revealing the important assisting role of a water molecule in its own dissociation process on a metal oxide. Inspired by the experimental findings, we theoretically model the oxygen evolution reaction activity of cobalt oxide nanoislands and show that the nanoparticle metal edges also display favourable adsorption energetics for water oxidation under electrochemical conditions. ©The Author(s) 2017.


Rondeau A.,PSN RES SCA | Merrison J.,Institute for Storage Ring Facilities | Iversen J.J.,Institute for Storage Ring Facilities | Peillon S.,PSN RES SCA | And 4 more authors.
Fusion Engineering and Design | Year: 2015

During the normal operating condition of the future ITER tokamak, a massive production of dust in the toroidal vacuum vessel is expected. This dust, originating from the erosion of tungsten and beryllium internal walls of the torus by the plasma, would be mobilized to some extent during a loss of vacuum accident (LOVA). For safety reasons, it is essential to quantify the re-suspended dust fraction during such an event. Here, we provide preliminary experimental data of dust re-suspension obtained in the wind tunnel of the European Space Agency (ESA) at low pressures (300, 130 and 10mbar). The experimentations were performed with multilayer deposits. We used two powders with a median diameter at 15.5μm and 21.8μm. A negative influence of the low pressure in the re-suspension mechanism is observed. For example, given a re-suspension fraction of 10%, increasing friction shear velocities are derived for decreasing absolute pressures: 300mbar/0.66ms-1; 130mbar/1.08ms-1; and 10mbar/1.84ms-1. In addition, we highlight the friction reduction for Kundsen numbers greater than 0.1 by an analysis of the airflow forces. © 2015 Elsevier B.V.


PubMed | University of Aarhus, University of Pennsylvania, University of Manchester, SLAC and Institute for Storage Ring Facilities
Type: | Journal: Nature communications | Year: 2017

Transition metal oxides show great promise as Earth-abundant catalysts for the oxygen evolution reaction in electrochemical water splitting. However, progress in the development of highly active oxide nanostructures is hampered by a lack of knowledge of the location and nature of the active sites. Here we show, through atom-resolved scanning tunnelling microscopy, X-ray spectroscopy and computational modelling, how hydroxyls form from water dissociation at under coordinated cobalt edge sites of cobalt oxide nanoislands. Surprisingly, we find that an additional water molecule acts to promote all the elementary steps of the dissociation process and subsequent hydrogen migration, revealing the important assisting role of a water molecule in its own dissociation process on a metal oxide. Inspired by the experimental findings, we theoretically model the oxygen evolution reaction activity of cobalt oxide nanoislands and show that the nanoparticle metal edges also display favourable adsorption energetics for water oxidation under electrochemical conditions.


Mazzola F.,Norwegian University of Science and Technology | Nematollahi M.,Norwegian University of Science and Technology | Li Z.S.,Institute for Storage Ring Facilities | Cooil S.,Norwegian University of Science and Technology | And 3 more authors.
Applied Physics Letters | Year: 2015

Resonant photoemission spectroscopy is used to study the intermediate-band material Cr doped ZnS. Using resonant photoemission, we show that the intermediate-band can be characterized, revealing the filling and specific orbital character of the states contributing to the resonant photoemission signal. We demonstrate that resonant photoemission spectroscopy is a powerful approach for understanding the origin of intermediate bands in doped ZnS. The methodology can be widely extended to a large variety of materials, providing useful information towards engineering of high efficiency intermediate band solar cells and of other optoelectronic devices. © 2015 AIP Publishing LLC.

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