Dehydriding and hydriding properties of 6LiBH4-CeCl3 composite

F. C. GENNARI; L. FERNÁNDEZ ALBANESI; J. A. PUSZKIEL; P. ARNEODO LAROCHETTE

Moscú, Rusia

Simposio; International Symposium on Metal-Hydrogen Systems-Fundamentals and Applications; 2010

Metal-Hydrogen Systems Association

Solid-state storage of hydrogen as borohydrides or tetrahydroborates has been attracting great interest as potential candidates for advanced hydrogen storage materials. Among them, LiBH4 has the highest theoretical hydrogen storage capacity (18.5 wt%) and desorbs about 13.8 wt% of hydrogen from the reaction LiBH4® LiH + B + 3/2 H2. However, both the temperature-pressure conditions and rate at which the hydrogen can be incorporated and released from LiBH4 are not suitable for on-board storage for vehicle purpose. For these reasons, recent efforts have focused on incorporating additives, such as metals, metal halides, oxides and hydrides to thermodinamically destabilize LiBH4 toward improved experimental conditions of reversibility. Recently, it was demonstrated that LiBH4 can be destabilized by mixing with MgH2 [1,2]. During dehydrogenation, the exothermic formation enthalpy of MgB2 stabilizes the dehydronated state, thereby destabilizing both LiBH4 and MgH2 and reducing the dehydriding temperature. Thus, the concept of thermodynamic destabilization appears to provide new possibilities for accessing the high hydrogen content of strongly bound hydrides. In this context, different LiBH4-based reactive hydrides composites are under investigation. In the present work, we study the hydrogen absorption/desorption properties of 6LiBH4-CeCl3 composite prepared by milling. The chemical interaction between CeCl3 and LiBH4 decreases the dehydrogenation temperature in comparison with as–milled LiBH4 by destabilization via CeH2 formation. Hydrogen desorption starts with the decomposition of Ce(BH4)3 formed during the milling process [3] and proceeds to the final formation of LiH and CeB6, which is confirmed by X-ray diffraction data. After rehydrogenation at 400 ºC under 6.0 MPa for 2 h, LiH and CeB6 are converted back to LiBH4-CeH2. The effect of hydrogen back pressure and microstructural characteristics of the composites on hydrogen absorption/desorption properties is analyzed.   References 1.  J. J. Vajo, S. L. Skeith and F. Mertens, J. Phys. Chem. B, 109, (2005), 3719-3722. 2. U. Boesenberg, S.  Doppiu, L. Mosegaard, G. Barkhordarian, N. Eigen, A. Borgschulte, T.R. Jensen, Y. Cerenius, O. Gutfleisch, T. Klassen, M. Dornheim, R. Bormann, Acta Mater., 55, (2007), 3951-3958. 3. F. C. Gennari and M. R. Esquivel, J. Alloys Compd., 485, (2009), L47-51.