Improved hydrogen storage performance of Mg(NH_2)_2/LiH mixture by addition of carbon nanostructured materials

摘要

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(NH_2)_2/LiH mixture have been studied. Amongst CNTs and CNFs, the improvement in the hydrogenation properties for the Mg(NH_2)_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 ZrFe_2 catalyst) and (b) CNF2 (synthesized using a LaNi_5 catalyst). The results show that CNF2 is better. The maximum decomposition temperature for the pristine Mg(NH_2)_2/LiH mixture is found to be ~ 250 ℃, which is reduced to ~ 180 and ~ 150 ℃ 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 mol~(-1) for the samples mixed with MWCNT and CNF2 respectively, whereas the activation energy for the dehydrogenation reaction of the pristine Mg(NH_2)_2/LiH mixture is 97 kJ mol~(-1). The catalytic activity and the de/re-hydrogenation characteristics of the Mg(NH_2)_2/LiH mixture mixed with different carbon nanostructures are described and discussed.