Effect of LaH_3-TiH_2 composite additive on the hydrogen storage properties of Mg_2Ni alloys

摘要

A novel LaH_3-TiH_2 composite additive was prepared by ball milling LaH_3 and TiH_2 at a 1:1 weight ratio. Kinetic measurements on the hydrogenation reaction indicated that the LaH_3-TiH_2 composite additive could significantly improve the hydrogen absorption properties of Mg_2Ni. In comparison with that of a pure Mg_2Ni alloy and a composite material combining Mg_2Ni + 10 wt.% LaH_3, the hydrogen storage capacity of the Mg_2Ni + 10 wt.% (LaH_3-TiH_2) composite was 0.251 wt.% and 0.559 wt.% higher at 423 K within 100 s, respectively. Moreover, the composite additive revealed an excellent effect on ameliorating the thermodynamic properties of the Mg_2Ni hydride. The decomposition onset temperature of the Mg_2. Ni + 10 wt.% (LaH_3-TiH_2) composite hydride was 17 and 13 K lower than that of the pure Mg_2NiH_4 and Mg_2Ni + 10 wt.% TiH_2 composite, respectively. X-ray diffraction (XRD) results indicated that the LaH_3 in the LaH_3-TiH_2 composite additive were converted to LaH_2 by the catalytic effect of TiH_2 during the hydrogenation cycles and that the process enhanced the kinetic properties of hydrogen storage for Mg_2Ni alloy.