Hydrogen-release mechanisms in LiNH2BH3•NH3BH3: A theoretical study

The molecular mechanism of the dehydrogenation of LiNH2BH3 center dot NH3BH3 to form [LiN2B2H] by the loss of five molar equiv of H-2 at two consecutive temperatures of 373 K and 501 K has been investigated using computational quantum chemistry methods (B3LYP, MP2 and CCSD(T) methods). The intermediate LiNHBH2 center dot NH2BH2 can be obtained through the pathway A at 373 K, in which LiH structures are formed by the transfer of hydridic H- from NH2BH3- to Li+ followed by the redox reactions of H delta+ and H delta- to form two molar equiv of H-2. The intermediate LiNH2BH=NHBH3 can also be generated via the pathway B at 373 K, in which a new N-B bond forms and two equiv of H-2 are released by the redox reactions. At 501 K, the predominant final product P-1 (LiNBNBH) is given most likely through the formation of LiH and a series of redox reactions with the loss of three molar equiv of H-2 in the pathway A Meanwhile, the products P-2 (LiNBBNH) and P-3 [Li( -NBBN-)H] may be also obtained by the dehydrogenation via a sequence of redox reactions of H delta+ and H delta- to release three equiv of H-2 at the temperature of 501 K. The present study would be helpful for experimental chemists to design better hydrogen-storage media. (C) 2014 Elsevier B.V. All rights reserved.