Mg-Ni-La based small hydrogen storage tank: kinetics, reversibility and reaction mechanisms

The improvement of de/rehydrogenation kinetics and reversibility of a Mg-Ni-La based small hydrogen storage tank by doping with TiF₄ and MWCNTs is reported for the first time. During sample preparation, MgH₂ milled with 20 wt% LaNi₅ and 5 wt% TiF₄ and MWCNTs produces Mg₂NiH₄ and LaH₃. Two-step dehydrogenation of Mg₂NiH₄ and MgH₂ is detected at 295 and 350 °C, respectively. Hydrogen desorption and absorption of the tank complete within 150 and 16 min, respectively, together with reversible hydrogen storage capacity up to 4.00 wt% H₂ (68% of theoretical value) upon 16 de/rehydrogenation cycles. Heat release from exothermic hydrogenation is removed effectively at the end of a double tube heat exchanger, where the reaction heat and heat transfer fluid are first in contact. Co-catalytic effects of Mg₂NiH₄ and LaH₃ as well as good hydrogen diffusion benefit dehydrogenation kinetics and reversibility of the tank.