The effect of different carbon nanostructures specifically carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on the improvement of the de/re-hydrogenation characteristics of a Mg(NH2)(2)/LiH mixture have been studied. Amongst CNTs and CNFs, the improvement in the hydrogenation properties for the Mg(NH2)(2)/LiH mixture is higher when CNFs are used as a catalyst. Investigations are also focused on the deployment of two different types of CNF (a) CNF1 (synthesized using a ZrFe2 catalyst) and (b) CNF2 (synthesized using a LaNi5 catalyst). The results show that CNF2 is better. The maximum decomposition temperature for the pristine Mg(NH2)(2)/LiH mixture is found to be similar to 250 degrees C, which is reduced to similar to 180 and similar to 150 degrees C for the sample mixed with 4 wt% of multi-walled carbon nanotubes (MWCNTs) and CNF2 respectively. The activation energy for the dehydrogenation reaction is found to be 74 and 68 kJ moll for the samples mixed with MWCNT and CNF2 respectively, whereas the activation energy for the dehydrogenation reaction of the pristine Mg(NH2)(2)/LiH mixture is 97 kJ mol(-1). The catalytic activity and the de/re-hydrogenation characteristics of the Mg(NH2)(2)/LiH mixture mixed with different carbon nanostructures are described and discussed. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.