Journal of Alloys and Compounds 446–447 (2007) 345–349 Hydrogen storage properties of 2LiNH 2 + LiBH 4 + MgH 2 Jun Yang a,∗ , Andrea Sudik a , Donald J. Siegel a , Devin Halliday a , Andy Drews a , Roscoe O. Carter III a , Christopher Wolverton a , Gregory J. Lewis b , J.W.A. Sachtler b , John J. Low b , Syed A. Faheem b , David A. Lesch b , Vidvuds Ozolins c a Ford Motor Company, Research and Advanced Engineering, MD 1170/RIC, Dearborn, MI 48121, USA b UOP LLC, 25 East Algonquin Road, Des Plaines, IL 60017-5017, USA c Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095-1595, USA Received 27 October 2006; received in revised form 21 March 2007; accepted 22 March 2007 Available online 5 April 2007 Abstract We have investigated the ternary mixture of complex hydrides with stoichiometry 2LiNH 2 + LiBH 4 + MgH 2 , and have identified a set of novel hydrogen storage reactions. One of these reactions involves the known reversible reaction Mg(NH 2 ) 2 + 2LiH ↔ Li 2 Mg(NH) 2 + 2H 2 . Previous stud- ies have shown that initiating this reaction from the binary mixture 2LiNH 2 + MgH 2 results in poor hydrogen desorption kinetics and a small amount of NH 3 release. In contrast to this behavior, here we demonstrate that by starting from the ternary mixture 2LiNH 2 + LiBH 4 + MgH 2 , the above reaction can proceed at lower temperatures and with improved kinetics, while maintaining reversibility. The advantage of start- ing with the ternary mixture can be traced to the subsequent formation, melting, and reaction of Li 4 BH 4 (NH 2 ) 3 with MgH 2 to form the mixed imide phase Li 2 Mg(NH) 2 , which acts as a seed for the reversible reaction, and is at least partly responsible for the improved kinetic response. © 2007 Elsevier B.V. All rights reserved. Keywords: Li 2 Mg(NH) 2 ; LiNH 2 ; LiBH 4 ; MgH 2 ; Hydrogen storage; Self-catalyzing 1. Introduction Complex hydrides such as NaAlH 4 , LiNH 2 and LiBH 4 are promising candidates for reversible solid-state hydrogen storage applications due to their high hydrogen densities. However, in their pure form the practical utility of most of these hydrides are limited by slow kinetics, irreversibility, and/or high desorp- tion temperatures. Recently, it has been recognized that a viable strategy for overcoming these limitations involves combining complex hydrides with small amounts of a catalytic dopant or via reactions with other compounds [1–3]. In regards to the later strategy, the reversible reaction involving amides and imides of lithium and magnesium, Mg(NH 2 ) 2 + 2LiH ↔ Li 2 Mg(NH) 2 + 2H 2 (1) ∗ Corresponding author. Tel.: +1 313 337 9803. E-mail address: jyang27@ford.com (J. Yang). has been found to have desirable thermodynamics for release and reabsorption of hydrogen at moderate temperatures and pressures [4,5]. However, the observed reaction kinetics of this reaction is inhibited, requiring temperatures of 220 ◦ C or more for reasonable rates of hydrogen release. Additionally, a small amount of NH 3 accompanies the release of H 2 , an undesir- able attribute as NH 3 can poison PEM fuel cells. In this paper, we will describe a novel scheme that results in significantly enhanced desorption kinetics for reaction (1) at lower tempera- tures while suppressing NH 3 release. These improved properties were identified in the course of exploring the ternary composi- tion, 2LiNH 2 + LiBH 4 + MgH 2 . 2. Experimental Lithium amide (LiNH 2 ) (95% purity, Sigma–Aldrich), magnesium hydride (MgH 2 ) (95% purity, Gelest) and lithium borohydride (LiBH 4 ) (95% purity, Sigma–Aldrich) were used as received. All sample handling was performed in an MBraun Labmaster 130 glovebox maintained under argon atmosphere with 0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2007.03.145