Mg50Ni-LiBH4 and Mg50Ni-LiBH4-CeCl3 composites have been prepared by short times of ball milling under argon atmosphere. Combination of HP-DSC and volumetric techniques show that Mg50Ni-LiBH4-CeCl3 composite not only uptakes hydrogen faster than Mg50Ni-LiBH4, but also releases hydrogen at a lower temperature (225 degrees C). The presence of CeCl3 has a catalytic role, but it does not modify the thermodynamic properties of the composite which corresponds to MgH2. Experimental studies on the hydriding/dehydriding mechanisms demonstrate that LiBH4 and Ni lead to the formation of MgNi3B2 in both composites. In addition. XRD/DSC analysis and thermodynamic calculations demonstrate that the addition of CeCl3 accounts for the enhancement of the hydrogen absorption/desorption kinetics through the interaction with LiBH4. The in situ formation and subsequent decomposition of Ce(BH4)(3) provides a uniform distribution of nanosize CeB4 compound, which plays an important role in improving the kinetic properties of MgH2. (C) 2009 Elsevier B.V. All rights reserved.