Young-Su Lee, High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea

CV of Young Su Lee

New Perspectives on Metal Borohydrides for Hydrogen Storage – Combined DFT and Experimental Study 

Hydrogen has received great attention for its use as a clean energy carrier that emits only water upon being burned to produce energy. One of the key ingredients for the widespread use of hydrogen is a safe and efficient means of storage. Metal borohydrides, M(BH4)n, have been intensively studied for such purpose. Against the expectation of its being a superb storage medium with high hydrogen capacity, the actual performance is plagued by high thermal stability and slow kinetics. 

Since the limited number of monometallic M(BH4)n provided by the periodic table, combinations of different metals, M(BH4)n and M’(BH4)n’, have been investigated to adjust their hydrogen storage thermodynamics. While it is still a hard task to find an optimal combination, bimetallic borodydride compounds such as LiK(BH4)2, NaSc(BH4)4, and KCa(BH4)3, to list a few, demonstrate fascinating diversity in crystal structure that may find applications in other area. In this talk, combined density functional theory calculations and experimental study to identify structural and thermodynamical properties of recently found bimetallic borohydrides will be presented. 

Nanoconfinement of borohydrides in porous scaffold materials (mostly carbon or silica based) is another approach to improve their hydrogen storage performance. This method has been proved to be effective, especially for LiBH4, and recent studies to elucidate the underlying mechanism discovered that ionic species become unusually mobile at the interface with scaffolding materials. Here again the composite of two borohydrides, for instance LiBH4-Ca(BH4)2, can enhance such effect by inducing eutectic melting and open up possibility for further manipulation of the property. Some theoretical efforts to probe borohydride-scaffold interaction at the atomistic level will be discussed.   

References

1. Lee et al., “Decomposition reactions and reversibility of the LiBH4-Ca(BH4)2 composite,” J. Phys. Chem. C 113, 15080 (2009).
2. Ley et al., “LiCe(BH4)3Cl, a new lithium-ion conductor and hydrogen storage material with isolated tetranuclear anionic clusters, ” Chem. Mater. 24, 1654 (2012).
3. Schouwink et al., “Structure and properties of complex hydride perovskite materials,” Nature Commun. 5, 5706 (2014).
4. Lee et al., “In Situ NMR Study on the Interaction between LiBH4–Ca(BH4)2 and Mesoporous Scaffolds,” J. Phys. Chem. Lett. 3, 2922 (2012).
5. Hwang et al., “Identifying the nature of interaction between LiBH4 and two-dimensional substrates: DFT study with van der Waals correction,” J. Alloys. Compd. 587, 428 (2014). 
6. Blanchard et al., “Nanoconfined LiBH4 as a fast lithium ion conductor,” Adv. Funct. Mater. 25, 184 (2015).
7. Hwang et al., “Probing molecular dynamics of metal borohydrides on the surface of mesoporous scaffolds by multinuclear high resolution solid state NMR,” J. Alloys. Compd. In press (2015).