Catalytic effect of multi-wall carbon nanotubes supported nickel on hydrogen storage properties of Mg₉₉Ni prepared by hydriding combustion synthesis

Multi-wall carbon nanotubes supported nickel (Nano-nickel/MWCNT) is added to the hydriding combustion synthesis (HCS) product of Mg₉₉Ni by mechanical milling to yield a designed composite for improving the hydrogen storage properties of magnesium. It is revealed that there is a synergistic effect of nano-Mg₂NiH₄and MWCNT on the hydrogen storage properties of Mg₉₉Ni, which improves the hydrogenation and dehydrogenation performance when compared to adding either nano-Ni or MWCNT alone. The composite requires only 80 s to reach its saturated hydrogen capacity of 6.79 mass% at 373K and desorbs 97.2% hydrogen within 1800 s at 543 K. The dehydrogenation activation energy of this system is 105 kJ mol^-1, which is much lower than that of as-received MgH₂(153 kJ mol^-1). In addition, the composite preserves stable hydrogen storage capacity and kinetics in the hydrogenation/dehydrogenation cycles at 423 K.