Effect of novel La-based alloy modification on hydrogen storage performance of magnesium hydride: First-principles calculation and experimental investigation

LaNi4.5X0.5(X = Fe, Co, Al, Ni) alloys are prepared and doped into MgH2 by ball milling to enhance the hydrogen storage performance, respectively. Both hydrogenation & dehydrogenation kinetics are experimentally measured, and the results indicate that LaNi4.5Fe0.5 doped MgH2 exhibits the top H2 absorption/desorption performance compared with other samples. It is worth noting that the optimal doping amount of LaNi4.5Fe0.5 is selected as 15 wt.% combined with the consideration of working temperature and H2 storage capacity. More importantly, the as-prepared MgH2-15 wt.%LaNi4.5Fe0.5 sample may rapidly introduce the equivalent H2 within 1000 s at mild temperature and pressure of 200 °C and 1 MPa, and it is completely impossible for MgH2 to occur any hydrogenation under this operation conditions. Moreover, the activation energy barriers for hydrogenation & dehydrogenation decline by 62.90% & 20.75% respectively, suggesting the successful doping and property of La-based alloy inside MgH2 as expected. In addition, a variety of as-prepared alloys are experimentally compared and discussed, and the related the heterostructure interface, electronic structure and the formation energy of H vacancy are carried out based on the first-principles calculation, which confirm that LaNi4.5Fe0.5 owns the most favorable catalytic modification effect on Mg-based material.