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Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed
Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, MB Eindhoven 5600, The Netherlands
Department of Electrical Engineering, Eindhoven University of Technology, MB Eindhoven 5600, The Netherlands
* Author to whom correspondence should be addressed.
Received: 18 April 2012; in revised form: 30 July 2012 / Accepted: 10 August 2012 / Published: 15 October 2012
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
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Manivasagam, T.G.; Kiraz, K.; Notten, P.H.L. Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed. Crystals 2012, 2, 1410-1433.
Manivasagam TG, Kiraz K, Notten PHL. Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed. Crystals. 2012; 2(4):1410-1433.
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.