Preparation of A₂B₇-type La-Mg-Ni Hydrogen Storage Alloy and Its Catalytic Oxidation Performance for BH₄^-

The La-Mg-Ni hydrogen storage alloys with A₂B₇/AB₅ double phase were successfully prepared by vacuum melting combined with ball milling. The phase structure, electrochemical properties and the catalytic oxidation properties for BH^4- of the (Mm_1-xMg_x)Ni_2.485Co_0.525Mn_0.28Al_0.21 (x=0.1-0.5 )alloys were investigated by XRD and electrochemical measurements. The results showed that (Mm_1-xMg_x)Ni_2.485Co_0.525Mn_0.28Al_0.21 alloys are composed of LaNi₅ phase and (La, Mg)₂Ni₇ phase. Among the studied alloys, the electrochemical properties of the alloy with x=0.3 is the best, and the electrochemical properties of the alloy with x=0.3 is significantly better than that of the AB₅-type hydrogen storage alloy, which is mainly due to the formation of (La, Mg)₂Ni₇ phase in the alloy. At the same time, the alloy with x=0.3 also shows a better catalytic oxidation effect on BH^4-, which is also better than that of the AB_5- type hydrogen storage alloy. The catalysis of (Mm_1-xMg_x)Ni_2.485Co_0.525Mn_0.28Al_0.21 alloy catalyst is related to its electrochemical performance. The catalysis of hydrogen storage alloys may have a positive correlation with its own electrochemical performance.