Phase stability and hydrogen desorption in a quinary equimolar mixture of light-metals borohydrides

The present study aims at investigating, for the first time, a quinary mixture of light-metals borohydrides. The goal is to design combinations of borohydrides with multiple cations in equimolar ratio, following the concept of high entropy alloys. The equimolar composition of the LiBH4-NaBH4-KBH4-Mg(BH4)(2)-Ca(BH4)(2) system was synthetized by ball milling. The obtained phases were analysed by X-ray diffraction and in-situ Synchrotron Radiation Powder X-ray Diffraction, in order to establish the amount of cations incorporated in the obtained crystalline phases and to study the thermal behaviour of the mixture. HP-DSC and DTA were also used to define the phase transformations and thermal decomposition reactions, leading to the release of hydrogen, that was detected by MS. The existence of a quinary liquid borohydride phase is reported for the first time. Effects of the presence of multi-cations compounds or a liquid phase on the hydrogen desorption reactions are described. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.