Sodium borohydride (SBH) and ammonia borane (AB) are promising hydrogen storage materials for portable fuel cell power systems. To release hydrogen from these compounds, thermolysis, catalytic hydrolysis, exothermic reactions with solid oxidizers or heat generated by additional reactive mixtures are usually employed. All the current methods have disadvantages which decrease the efficiency of hydrogen storage systems. In the present paper, we report new approaches to release hydrogen from SBH or AB, and simultaneously from water, which do not require any catalyst and produce relatively high hydrogen yield and environmentally benign byproducts. One such approach involves metal/water combustion reactions, which provide heat for SBH or AB dehydrogenation and release additional hydrogen from water [1]. The other approach thermally activates AB hydrolysis in aqueous AB solutions under modest inert gas pressure [2]. The investigations include digital video recording, pressure monitoring, thermocouple measurements, gas chromatography, mass spectrometry, powder XRD analysis, NMR spectroscopy and isotopic (deuterium) labeling. The results show that the proposed methods are promising for hydrogen storage involving SBH or AB. The metal/water combustion methods could be used in compact power sources for portable electronic devices, while hydrothermolysis in aqueous AB solutions is attractive for applications where off-board water is used, such as ship propulsion or power generation in a remote location, and vehicle transportation.

References:

[1] Shafirovich, E., Diakov, V., and Varma, A., “Combustion–assisted hydrolysis of sodium borohydride for hydrogen generation”, International Journal of Hydrogen Energy, Vol.32, 2007, pp. 207-211.

[2] Diwan, M., Diakov, V., Shafirovich, E., Varma, A., “Noncatalytic Hydrothermolysis of Ammonia Borane”, International Journal of Hydrogen Energy, Vol. 33, 2008, pp 1135-1141.