Thermodynamic and kinetic properties of potassium alanate (KAlH 4 ) are investigated. Its pressure-compositionisotherm measurement exhibits two plateaus for hydrogen absorption/desorption in KAlH 4 , with gravimetric hydrogen densities of 1.2 ( 0.1 and 2.6 ( 0.2 mass% and reaction enthalpies of 81 and 70 kJ • mol -1 H 2 , respectively. However, the nonisothermal decomposition of KAlH 4 occurs through three endothermic events at temperatures of 294, 311, and 347 °C with the release of hydrogen. Whereas the high temperature event is clearly attributed to K 3 AlH 6 decomposition, the low temperature events occur by two reactions, denoting the existence of an intermediate phase during KAlH 4 decomposition. FTIR measurements suggest that this intermediate phase is a K y AlH x compound (y g 1, x g 4) with a high coordination about the aluminum. TiCl 3 -doped KAlH 4 also exhibits three decomposition events, but with significant reduction of desorption temperatures (∼50 °C) as well as activation energies that is attributed to particle size reduction and creation of charged vacancies.

Ethane 1,2-diamineborane (BH3­NH2­CH2­CH2­NH2­BH3, EDAB hereafter) samples have been synthesized by reacting ethylenediamine dihydrochloride with sodium borohydride in tetrahydrofuran solution. Structural and bonding properties of EDAB have been characterized by liquid-state nuclear magnetic resonance, X-ray powder diffraction, and vibrational spectroscopy (infrared and Raman). The thermolytic decomposition of EDAB has been investigated by means of combined thermogravimetry, differential thermal analysis, and mass spectrometry measurements, both under vacuum and inert gas flow conditions. These experiments allow the determination of the enthalpies and activation energies of two hydrogen desorption stages below 520 K as well as the yields and purity of the released gases. These results show that EDAB presents a thermal stability, both under vacuum and under inert gas flow, higher than that of its parent counterparts methylamine borane (BH3NH2CH3) and ammonia borane (BH3NH3). Contrary to those compounds, EDAB releases pure hydrogen when heated under inert flow. In contrast, moderate fractions of diborane, residual tetrahydrofuran, and volatile B–N–C–H species are released when conducting the experiments under dynamic vacuum. In situ temperature-programmed infrared spectroscopy measurements using synchrotron radiation and operando Raman-mass spectrometry experiments provide insight into the EDAB thermolysis reaction mechanism.

The "art" of material design for hydrogen storage relies on mastering divergent requirements. This review aims to summarise recent strategies to design better hydride materials toward the storage and use of hydrogen as a clean energy carrier.

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