Nanoconfinement significantly improves the thermodynamics and kinetics of co-infiltrated 2LiBH4-LiA1H4 composites: Stable reversibility of hydrogen absorption/resorption

A uniformly distributed composite of 2LiBH(4)-LiA1H(4) was successfully nanoconfined in mesoporous carbon scaffolds by using the solvent-mediated infiltration technique. The onset dehydrogenation temperatures of LiA1H(4) and LiBH4 in the infiltrated 2LiBH(4)-LiA1H(4) composite are decreased to 80 and,-,230 C, respectively, and are 40 and 145 degrees C lower for their post-milled counterparts. Isothermal measurements reveal that,,,10 wt.% H2 could be released from the nanoconfined 2LiBH(4)-LiA1H(4) composite at 300 degrees C within 300 min, while less than 4 wt.% H2 was released with respect to the post-milled mixture, even at 350 C. Moreover, by taking advantage of both nanoconfinement and thermodynamic destabilization, the release of toxic diborane from LiBH4 was successfully suppressed. The dehydrogenation mechanism reveals that, under the structure-directing effects of carbon supports, the decomposition of the well-distributed 2LiBH4 LiA1H4 composite favors the formation of A1B2 instead of the thermodynamically stable Li2l3121112, which has been verified to play a crucial role in enhancing the hydrogenation of the 2LiBH4 LiA1H4 composite. In combination with the extra LiH supplied by the in situ decomposition of nanoconfined LiA1H4, the thus-tailored thermodynamics and kinetics of the 2LiBH4 LiA1H4 composite endow it with significantly advanced reversible hydrogen storage properties, with a stable reversibility without apparent degradation after seven dehydrogenation/rehydrogenation cycles.(C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.