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Electronic Principles of Hydrogen Incorporation and Dynamics in Metal Hydrides
Crystals 2012, 2(4), 1410-1433; doi:10.3390/cryst2041410
Review

Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed

1,* , 1
 and 1,2
Received: 18 April 2012; in revised form: 30 July 2012 / Accepted: 10 August 2012 / Published: 15 October 2012
(This article belongs to the Special Issue Hydrogen Storage Alloys)
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Abstract: As potential hydrogen storage media, magnesium based hydrides have been systematically studied in order to improve reversibility, storage capacity, kinetics and thermodynamics. The present article deals with the electrochemical and optical properties of Mg alloy hydrides. Electrochemical hydrogenation, compared to conventional gas phase hydrogen loading, provides precise control with only moderate reaction conditions. Interestingly, the alloy composition determines the crystallographic nature of the metal-hydride: a structural change is induced from rutile to fluorite at 80 at.% of Mg in Mg-TM alloy, with ensuing improved hydrogen mobility and storage capacity. So far, 6 wt.% (equivalent to 1600 mAh/g) of reversibly stored hydrogen in MgyTM(1-y)Hx (TM: Sc, Ti) has been reported. Thin film forms of these metal-hydrides reveal interesting electrochromic properties as a function of hydrogen content. Optical switching occurs during (de)hydrogenation between the reflective metal and the transparent metal hydride states. The chronological sequence of the optical improvements in optically active metal hydrides starts with the rare earth systems (YHx), followed by Mg rare earth alloy hydrides (MgyGd(1-y)Hx) and concludes with Mg transition metal hydrides (MgyTM(1-y)Hx). In-situ optical characterization of gradient thin films during (de)hydrogenation, denoted as hydrogenography, enables the monitoring of alloy composition gradients simultaneously.
Keywords: hydrogen storage; magnesium hydride; switchable mirrors; bulk powders; thin films; electrochemical hydrogenation; gas phase hydrogenation hydrogen storage; magnesium hydride; switchable mirrors; bulk powders; thin films; electrochemical hydrogenation; gas phase hydrogenation
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Manivasagam, T.G.; Kiraz, K.; Notten, P.H.L. Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed. Crystals 2012, 2, 1410-1433.

AMA Style

Manivasagam TG, Kiraz K, Notten PHL. Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed. Crystals. 2012; 2(4):1410-1433.

Chicago/Turabian Style

Manivasagam, Thirugnasambandam G.; Kiraz, Kamil; Notten, Peter H.L. 2012. "Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed." Crystals 2, no. 4: 1410-1433.


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