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YMgGa as a hydrogen storage compound
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. (Oorganisk kemi)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. (Oorganisk kemi)
2009 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 182, no 7, 1833-1837 p.Article in journal (Refereed) Published
Abstract [en]

The hydrogen absorption and desorption properties of the recently found ternary phase YMgGa have been studied. This compound absorbs 2.2 wt% hydrogen during the first cycle, but only 1.1 wt% can be stored reversibly for the following cycles under the applied pressure and temperature conditions. Hydrogen absorption and desorption properties were investigated by measuring the thermal desorption spectra and the pressure-composition isotherms while the crystal structure was determined using X-ray diffraction (XRD). The compound absorbs hydrogen at pressures above 0.2 MPa and 250 °C by decomposing into YH3 and MgGa. This reaction is reversed when heating the hydride in a He atmosphere; hydrogen is released and the YMgGa phase is partially recovered together with YGa2 and YH2. The reformation of YMgGa occurs at temperatures below 450 °C on the expenses of hydrogen desorption from YH2. This is not expected under these temperature conditions as YH2 normally does not desorb hydrogen below 800 °C.

Place, publisher, year, edition, pages
Elsevier , 2009. Vol. 182, no 7, 1833-1837 p.
Keyword [en]
Magnesium intermetallics, Hydrides, Hydrogen storage, X-ray diffraction, (XRD)
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-107417DOI: 10.1016/j.jssc.2009.04.029ISI: 000267717600034OAI: oai:DiVA.org:uu-107417DiVA: diva2:229157
Available from: 2009-08-11 Created: 2009-08-11 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Light-Metal Hydrides for Hydrogen Storage
Open this publication in new window or tab >>Light-Metal Hydrides for Hydrogen Storage
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Demands for zero greenhouse-gas emission vehicles have sharpened with today’s increased focus on global warming. Hydrogen storage is a key technology for the implementation of hydrogen powered vehicles. Metal hydrides can claim higher energy densities than alternative hydrogen storage materials, but a remaining challenge is to find a metal hydride which satisfies all current demands on practical usability. Several metals store large amounts of hydrogen by forming a metal hydride, e.g., Mg, Ti and Al. The main problems are the weight of the material and the reaction energy between the metal and hydrogen.

Magnesium has a high storage capacity (7.6 wt.% hydrogen) in forming MgH2; this is a slow reaction, but can be accelerated either by minimizing the diffusion length within the hydride or by changing the diffusion properties. Light-metal hydrides have been studied in this thesis with the goal of finding new hydrogen storage compounds and of gaining a better understanding of the parameters which determine their storage properties. Various magnesium-containing compounds have been investigated. These systems represent different ways to address the problems which arise in exploiting magnesium based materials. The compounds were synthesized in sealed tantalum tubes, and investigated by in situ synchrotron radiation X-ray powder diffraction, neutron powder diffraction, isothermal measurements, thermal desorption spectroscopy and electron microscopy.

It is demonstrated that hydrogen storage properties can be improved by alloying magnesium with yttrium or scandium. Mg-Y-compounds decompose in hydrogen to form MgH2 nano-structures. Hydrogen desorption kinetics are improved compared to pure MgH2. The influence of adding a third element, gallium or zinc has also been studied; it is shown that gallium improves hydrogen desorption from YH2. ScAl1-xMgx is presented here for the first time as a hydrogen storage material. It absorbs hydrogen by forming ScH2 and Al(Mg) in a fully reversible reaction. It is shown that the hydrogen desorption temperature of ScH2 is reduced by more than 400 °C by alloying with aluminium and magnesium.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 666
Keyword
Metal-hydrogen compounds, hydrides, hydrogen storage, X-ray diffraction, neutron diffraction, thermal desorption spectroscopy
National Category
Chemical Sciences Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-107380 (URN)978-91-554-7585-7 (ISBN)
Public defence
2009-09-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-09-04 Created: 2009-08-10 Last updated: 2009-09-04Bibliographically approved

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Sahlberg, Martin

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