The Influence Of MoS₂on The Phase Structure And Hydrogen Storage Properties Of Magnesium-based Alloys

The main advantages of magnesium-based hydrogen storage materials include highhydrogen storage capacity （7.6wt.%）, abundance as well as low cost. The materials havebeen investigated for the past decades, however, it cannot be widely applied because of thehigh hydrogen absorption and decomposition temperature and the poor kinetics. In thispaper, a series of composites were prepared using mechanically ball milling, of which thephase structures, kinetics and dehydrogenation thermal desorption were investigated.MoS₂can significantly improve the kinetics performance of MgH₂. At423K, theMgH₂with MoS₂absorbs2.7wt.%hydrogen within800s, while the as-milled MgH₂absorbs only0.7wt.%hydrogen under the same experimental conditions. For dehydrogenkinetic of MgH₂with MoS₂,0.55wt.%hydrogen can be desorbed within600s at423K,however, only0.1wt.%of hydrogen is desorbed of the as-milled MgH₂. Based on theKissinger plot, the activation energy of the hydrogen desorption processes of MgH₂reduces by23.84kJ·mol^-1due to the addition of MoS₂, indicating that the dehydridingprocess energy barrier of MgH₂can be reduced with the catalytic effect of MoS₂. MoS₂reacts with MgH₂to in-situ produce MgS and Mo phases during ball milling process, MgSand Mo phases are found to be stable and always exist in the hydriding/dehydridingprocesses. The MgS and Mo play a synergistic role in facilitating the kineticsimprovement of MgH₂.The LaH₃and MgH₂are produced after dehydrogenation of LaMg₃alloy. The effectof LaH₃and MoS₂in catalyzing MgH₂are studied. The LaMg₃+17wt.%MoS₂compositeis prepared by ball milling. MoS₂reduces the onset dehydrogenation temperaturesignificantly and ameliorates the kinetics performance of LaMg₃alloy. At423K, thecomposite achieves80%of the maximum hydrogen storage amount is10s, while theLaMg₃alloy takes60s. The dehydrogen time for content to reach80%of maximumstorage capacity for the composite is240s at573K, while the LaMg₃alloy is450s. Theonset dehydrogenation temperature of LaMg₃alloy reduces58K due to the addition ofMoS₂. The storage performance improvement of LaMg₃alloy is due to the catalysis ofLaH₃and the synergistic effect of MgS and Mo. The hydrogen storage property of LaMg_7.25Ni_1.75with MoS₂is investigated. At473K,the uptime for hydrogen content to reach80%of maximum hydrogen storage capacity forthe composite is50s, while the LaMg_7.25Ni_1.75alloy is100s at the same condition. P-C-Ttest shows that platform pressure of Mg₂Ni phase for the composite is higher than that forthe LaMg_7.25Ni_1.75alloys. The dehydriding enthalpy of Mg₂Ni phase for the composite isless than that for LaMg_7.25Ni_1.75alloy. This proves that Mg₂NiH₄of the composite is easierto decompose. The DSC shows the onset dehydrogenation temperature of LaMg₃alloyreduces about10K due to the addition of MoS₂.