Protide compounds in hydrogen storage systems

Structure and Properties of NaBH4·2H2O and NaBH4

“…In anhydrous NaBH 4 , the disordered BH 4 -anion symmetrically μ 2 -coordinates Na atoms at Na-H distances of 2.59 Å. Although Na···B contacts in NaBH 4 ·2H 2 O are only slightly shorter than in NaBH 4 [3.0654(1) Å], the Na···Na distances are considerably shortened from 4.34 to 3.61-3.80 Å. This is due to the fact that sodium atoms in NaBH 4 ·2H 2 O do not form a close-packed substructure as in the anhydrous NaBH 4 , but instead they form flat honeycomb layers in the ab plane.…”

“…Hydrogen can be produced from metal hydrides by thermal decomposition (pyrolysis) [1] or in a reaction with water (hydrolysis). [2] Borohydrides of alkaline metals, such as LiBH 4 and NaBH 4 , readily evolve hydrogen by hydrolysis, both upon direct reaction with water [3] and through a fuel cell. [4] Although the reactions with water are usually fast, the reaction kinetics under practical conditions is rather slow, thus suggesting the use of expensive catalysts.…”

“…[2] Borohydrides of alkaline metals, such as LiBH 4 and NaBH 4 , readily evolve hydrogen by hydrolysis, both upon direct reaction with water [3] and through a fuel cell. [4] Although the reactions with water are usually fast, the reaction kinetics under practical conditions is rather slow, thus suggesting the use of expensive catalysts. [5] Catalytically accelerated NaBH 4 hydrolysis for the generation of hydrogen has been studied since the 1950s, [6] and it is now under intensive investigation, [5] leading to a number of recent applications.…”

“…[4] Although the reactions with water are usually fast, the reaction kinetics under practical conditions is rather slow, thus suggesting the use of expensive catalysts. [5] Catalytically accelerated NaBH 4 hydrolysis for the generation of hydrogen has been studied since the 1950s, [6] and it is now under intensive investigation, [5] leading to a number of recent applications. [7] However, until now, there is no experimental structural information on intermediate phases or reaction pathways in the NaBH 4 + H 2 O system.…”

“…[8] Recently, the existence of short dihydrogen bonds has been reported for NaBH 4 ·2H 2 O from neutron diffraction, [9] but a full account of the structural data has not been published until now. Hydrogen elimination from LiBH 4 and NaBH 4 complexes with less-reactive proton donors, such as alcohols, has been reported, [10] whereas the study of the NaBH 4 complex with water would be very important for hydrogen storage. This work is focused on the crystal structure of NaBH 4 ·2H 2 O and its anhydrous counterpart and will contribute to a better understanding of the mechanism of borohydride hydrolysis.…”