Kinetics of hydrogen release from dissolutions of ammonia borane in different ionic liquids María Jos  e Valero-Pedraza, Alexandra Martín-Cort  es, Alexander Navarrete, María Dolores Bermejo,  Angel Martín * Department of Chemical Engineering and Environmental Technology, University of Valladolid, c/Doctor Mergelina s/n, 47011 Valladolid, Spain article info Article history: Received 19 May 2015 Received in revised form 16 July 2015 Accepted 30 August 2015 Available online 22 September 2015 Keywords: Hydrogen storage Hydrogen economy Ammonia borane Hydride Ionic liquid Kinetics abstract Ammonia borane is a promising hydrogen storage material that liberates hydrogen by thermolysis at moderate temperatures, but it also presents major limitations for practical applications including a long induction time before the initiation of hydrogen release and a difficult regeneration. Previous works have demonstrated that by dissolution of ammonia borane into several ionic liquids, and particularly in 1- butyl-3-methylimidazolium chloride bmimCl, the induction period at the beginning of the thermolysis is eliminated, but some problems persist, including foaming and the formation of a residue after ther- molysis that is insoluble in the ionic liquid. In this work, the release of hydrogen from ammonia borane dissolved in different ionic liquids has been analyzed, measuring the kinetics of hydrogen release, visually following the evolution of the sample during the process using pressure glass tube reactors, and analyzing the residue by spectroscopic techniques. While dissolutions of ammonia borane in most ionic liquids analyzed show similar properties as dissolutions in bmimCl, using ionic liquids with bis(tri- fluoromethylsulfanyl)imide Tf 2 N anion the foaming problem is reduced, and in some cases the residue remains dissolved in the ionic liquid, while with ionic liquids with choline anion higher hydrogen yields are achieved that indicate that the decomposition of ammonia borane proceeds through a different path. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction In the near future, renewable energies will have to be adopted as the main source of energy due to the depletion of fossil resources. Establishing a new energy system based on renewable resources is a challenging task for several reasons, including the fluctuating nature of many renewable energy sources such as wind and sun. The direct use of renewable energies in vehicles and other mobile applications is also problematic. A possible solution for some of these problems could be to use hydrogen as an energy carrier [1,2]. Hydrogen is a very attractive fuel because it combusts very cleanly, producing only water. Hydrogen can be produced by the electrolysis of water using renewable resources. It can then be stored for use during periods lacking in direct generation of energy in renewable power plants, or transported and used in vehicles or other mobile applications. To make this new paradigm a feasible reality, several technical issues must be solved, including the efficient production of hydrogen by electrolysis of water or from renewable biological sources, the conversion of hydrogen into electricity using improved fuel cells, and the storage of hydrogen [3e5]. In particular, storing hydrogen in small mobile applications or in vehicles presents significant challenges, as some of the obvious solutions such as storage as compressed gas or cryogenic liquid are limited with respect to the storage capacities or energy consump- tions. For these reasons, in recent years a considerable effort has been made to develop new hydrogen storage systems by different approaches, including metallic and chemical hydrides, carbon nanotubes, hydrates or metal-organic frameworks [6e9]. Among the different hydrogen storage materials, chemical and metallic hydrides are some of the most promising alternatives [10,11]. One of the most extensively studied hydrides is AB (ammonia borane), which is relatively stable, safer and easier to handle than other more reactive hydrides, and can release up to 13 wt% of hydrogen at temperatures below 180  C according to the following global reaction [12]: n(NH 3 BH 3 ) 4 (NH 2 BH 2 )n þ nH 2 4 (NHBH) n þ 2nH 2 (1) * Corresponding author. Tel.: þ34 983184077; fax: þ34 983423013. E-mail address: mamaan@iq.uva.es (  A. Martín). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2015.08.106 0360-5442/© 2015 Elsevier Ltd. All rights reserved. Energy 91 (2015) 742e750