Diborane, hydrogen storage

Zinc borohydride as an example of a transition metal compound contains 8.5 wt.% H2. The decomposition temperature of about 85 °C is quite low and is associated with the simultaneous melting of the compound. Between 85 and 140 °C an endothermic decomposition starts which is accompanied by the liberation of hydrogen and significant amounts of diborane. This excludes the use of Zn(BH4)2 for solid hydrogen storage [51]. 

Boron hydrides do have high hydrogen contents. However, the thermodynamics is in most cases unfavorable, the kinetics or the dehydrogenation and rehydrogenation are slow and the possible evolution of diborane is an additional problem. Therefore boron hydrides do not at present not allow any use as reversible hydrogen storage material. 

Hough WV et al (1956) The sodium-diborane reaction. J Am Chtan Soc 78 689 Ortega JV et al (2005) Triborohydride salts as hydrogen storage materials and preparation thereof. Patent US 2005/0135996 Al... 

Chlorides. Contact of 75% phosphoric acid containing traces of chlorides within a closed storage tank may liberate hydrogen, which will explode on ignition.3 4 Nitromethane. Mixtures of nitromethane and phosphoric acid can be detonated.5 Sodium Borohydride. Generation of diborane by addition of sodium borohydride to anhydrous phosphoric acid may be dangerously violent.6... 

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