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Activation effects during hydrogen release and uptake of MgH2
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-4752-5491
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2014 (English)In: International journal of hydrogen energy, ISSN 0360-3199, Vol. 39, no 18, 9888-9892 p.Article in journal (Refereed) Published
Abstract [en]

Scandium(II)hydride, ScH2, and scandium(III)chloride, ScCl3, are explored as additives to facilitate hydrogen release and uptake for magnesium hydride. These additives are expected to form more homogeneous composites with Mg/MgH2 as compared to metallic scandium. However, scandium(III)chloride, reacts with MgH2 during mechano-chemical treatment and form ScH2 and MgCl2 (that later crystallise during heat treatment). The composite MgH2-ScH2 was investigated using in-situ synchrotron radiation powder X-ray diffraction during up to five cycles of continuous release and uptake of hydrogen at isothermal conditions at 320, 400 and 450 degrees C and p(H-2) = 100-150 or 10(-2) bar. The data were analysed by Rietveld refinement and no reaction is observed between either MgH2/ScH2 or Mg/ScH2 during cycling. The extracted sigmoidal shaped curves for formation or decomposition of Mg/MgH2 suggest that a nucleation process is preceding the crystal growth. The reaction rate increases with increasing number of cycles of hydrogen release and uptake at isothermal conditions possibly due to activation effects. This kinetic enhancement is strongest between the first cycles and may be denoted an activation effect. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
2014. Vol. 39, no 18, 9888-9892 p.
Keyword [en]
Hydrogen storage, Magnesium hydride, Scandium(II)hydride, Scandium(III)chloride, In situ synchrotron powder X-ray diffraction
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-229295DOI: 10.1016/j.ijhydene.2014.02.112ISI: 000337859700039OAI: oai:DiVA.org:uu-229295DiVA: diva2:736386
Available from: 2014-08-06 Created: 2014-08-05 Last updated: 2015-09-07
In thesis
1. Structural Basis for Hydrogen Interaction in Selected Metal Hydrides
Open this publication in new window or tab >>Structural Basis for Hydrogen Interaction in Selected Metal Hydrides
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Metal hydrides have existing and potential uses in many applications such as in batteries, for hydrogen storage and for heat storage. New metal hydrides and a better understanding of the behaviour of known metal hydrides may prove crucial in the realisation or further development of these applications. The aims of the work described in this thesis have been to characterise new metal hydrides, investigate how the properties of known metal hydrides can be improved and understand how their structure influences these properties. Metal hydrides, in most cases synthesised via high-temperature techniques, were structurally characterised using X-ray powder diffraction, X-ray single crystal diffraction and neutron powder diffraction and their thermodynamic and kinetic properties by in-situ X-ray powder diffraction, thermal desorption spectroscopy and pressure-composition-temperature measurements.

The investigations showed that: the storage capacity of the hexagonal Laves phase Sc(Al1-xNix)2 decreases with increasing Al content. There is a significant decrease in the stability of the hydrides and faster reaction kinetics when Zr content is increased in the cubic Laves phase Sc1-xZrx(Co1-xNix)2. Nb4M0.9Si1.1 (M=Co, Ni) form very stable interstitial hydrides which have very slow sorption kinetics. MgH2 mixed with 10 mol% ScH2 reaches full activation after only one cycle at 673 K while it takes at least four cycles at 593 K. LnGa (Ln=Nd, Gd) absorb hydrogen in two steps, it is very likely that the first step is interstitial solution of hydride ions into Ln4 tetrahedra and the second step places hydrogen atoms in Ln3Ga tetrahedra. The nature of the Ga-H bond is still unclear.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 74 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1234
National Category
Metallurgy and Metallic Materials Materials Chemistry Inorganic Chemistry
urn:nbn:se:uu:diva-245046 (URN)978-91-554-9187-1 (ISBN)
Public defence
2015-04-24, Häggsalen, Ångströmlaboratoriet Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Swedish Research Council
Available from: 2015-04-01 Created: 2015-02-24 Last updated: 2015-09-07

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Ångstrom, JonasSahlberg, Martin
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