Hydrogen Storage Compounds

Materials-based hydrogen storage enables high volumetric densities and gravimetric densities of hydrogen. Challenges, however, remain related to developing compounds that simultaneously have high hydrogen capacities, low dehydrogenation temperature, controllable H2 release kinetics and good regeneration capability.  Boron Molecular is teaming up with the University of Wollongong to help the research community to search for the right candidates by enabling them to readily access high quality hydrogen storage compounds.

Sodium octahydrotriborate (NaB3H8) (BM1607)

Empirical Formula:  NaB3H8

Molecular Weight:  63.4

Description:  

White powder. Decomposes around 100 ºC under inert atmosphere. Slowly reacts with water (less than 10 % in one week at ambient temperature). Highly hygroscopic.  Highly soluble in most ethereal solvents.

Application

Sodium octahydrotriborate (NaB3H8) is a salt with high hydrogen content. It has a high solubility and reasonable stability in water. A rapid release of high purity H2 gas can be obtained through hydrolysis facilitated by transition metal based catalysts.

The high Na to B ratio leads to the formation of complex polyborate mixture during hydrolysis, and this metastable solution is difficult to crystallize (Figure 1). Compared to NaBH4 and NH3BH3, both of which tend to form hydrolytic products with low solubility in water, NaB3H8 can provide a greater storage capacity of hydrogen while maintaining a liquid phase. Liquid phase hydrogen storage has better compatibility with the current liquid fuel dispersion techniques.

                                                                     

Fig. 1 The formation of ployborates during the hydrolysis of NaB3H8.

The bulky B3H8 anion also makes it an ideal source to make hydrogen-rich ionic liquids.

Different from NaBH4, NaB3H8 is highly soluble in most ethereal solvents, including diethyl ether, and therefore can be an effective reducing agent in organic synthesis. 

It is an important precursor to other metal and nonmetal octahydrotriborates, whose high reactivity has made them interesting for the fabrication of boride thin films.

References:

1.  Z. Huang, G. King, X. Chen, J. Hoy, T. Yisgedu, H. Lingam, S. Shore, P. Woodward, J. Zhao. “A Simple and Efficient Way to Synthesize Unsolvated Sodium Octahydrotriborate.” Inorganic Chemistry, 2010, 49, 8185.

2. Z. Huang, X. Chen, T. Yisgedu, J. Zhao, S. Shore. “High-capacity hydrogen release through hydrolysis of NaB3H8.” International Journal of Hydrogen Energy, 2011, 36, 7038.

3.  D. Schubert, D. Neiner, M. Bowden, S. Whittemore, J. Holladay, Z. Huang, T. Autrey, “Capacity Enhancement of Aqueous Borohydride Fuels for hydrogen storage in liquids”, Journal of Alloys and Compounds, 2015, 645, S196.

4.  W. Chen, Z. Huang, G. Wu, T. He, Z. Li, J. Chen, Z. Guo, H Liu, P. Chen, “Guanidinium octahydrotriborate: an ionic liquid with high hydrogen storage capacity”, Journal of Materials Chemistry A, 2015, 3, 11411