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

Abstract

The improvement of de/rehydrogenation kinetics and reversibility of a Mg-Ni-La based small hydrogen storage tank by doping with TiF4and MWCNTs is reported for the first time. During sample preparation, MgH2milled with 20 wt% LaNi5and 5 wt% TiF4and MWCNTs produces Mg2NiH4and LaH3. Two-step dehydrogenation of Mg2NiH4and MgH2is 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 Mg2NiH4and LaH3as well as good hydrogen diffusion benefit dehydrogenation kinetics and reversibility of the tank.