A comparative study for synthesis methods of nano-structured (9Nie2MgeY) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH 2 Mehdi Pourabdoli a,b , Shahram Raygan a, *, Hossein Abdizadeh a , Deniz Uner b a School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran b Department of Chemical Engineering, Middle East Technical University, Ankara, Turkey article info Article history: Received 9 June 2013 Received in revised form 28 September 2013 Accepted 2 October 2013 Available online 1 November 2013 Keywords: Hydrogen storage Magnesium hydride Hydrogen desorption Catalyst Nano-structure abstract 9Nie2MgeY alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Nie2MgeY alloy due to high losses of Mg and Y. Therefore, 9Nie2MgeY alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying þ solid state reaction þ ball milling, and 3) mixing þ solid state reaction þ ball milling. The prepared 9Nie2MgeY alloy powders were compared for their catalytic effects on hydrogen desorption of MgH 2 . It is found that 9Ni e2MgeY alloy powder prepared by mechanical alloying þ solid state reaction þ ball milling method has a smaller particle size (1e5 mm) and higher surface area (1.7 m 2 g 1 ) than that of other methods. H 2 desorption tests revealed that addition of 9Nie2MgeY alloy prepared by mechanical alloying þ solid state reaction þ ball milling to MgH 2 decreases the hydrogen desorption temperature of MgH 2 from 425 to 210  C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350  C during 8 min. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Mg is considered one of the most promising candidates for hydrogen storage due to its high hydrogen storage capacity of 7.6 wt.%, high energy density (9 M J kg 1 Mg), reversible hydrogen absorption/desorption, abundance, heat resistant, non-toxicity and vibration absorbing properties [1e4]. How- ever, there are some properties of Mg that limit its practical use as a hydrogen storage material. The large negative enthalpy of formation results in a stable Mg hydride phase [5,6]. Also, hydrogen dissociation on the metallic Mg surface is an activated process with a high activation barrier resulting in a slow chemisorption process [7]. Methods such as high energy ball milling and various ad- ditives are used to improve magnesium hydride hydrogena- tion/dehydrogenation properties. Ball milling treatment increases hydriding kinetics by a factor of approximately 10 and addition of additives as catalyst may increase kinetics by another order of magnitude. As ball milling breaks down the particles, a higher surface area is present for hydrogen to * Corresponding author. Tel.: þ98 21 82084099; fax: þ98 21 88006076. E-mail addresses: shraygan@ut.ac.ir, sraygan@yahoo.com (S. Raygan). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 38 (2013) 16090 e16097 0360-3199/$ e see front matter Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijhydene.2013.10.010