Comparative study on the hydrogen storage performance of as-milled MgRENi rapid quenched alloy catalyzed by metal sulfides

The composites of Mg20Pr1Sm3Y1Ni10 as-quenched alloy and 3 wt.% M (M = CoS, CoS2, MoS2) catalyst were prepared by high-speed vibration ball mill. The effects of metal sulfides on the hydrogenation and dehydrogenation dynamics of alloys were compared. The results show that the as-milled composites contain a large number of amorphous embedded by a small amount of nanocrystals, and there are many point defects. After ball milling, the crystal grain size in the composites containing CoS is relatively larger, followed by CoS2 and MoS2 again. After hydrogenation, the amorphous phase is crystallized to form Mg2NiH4, YH3, Pr8H18.96, Sm3H7, Mg, Co or Mo phases, however, Mg2Ni, YH2, PrH2 and Ni3Y phases appeared after dehydrogenation. The maximum hydrogenation capacity of the composites containing CoS, CoS2 and MoS2 are 3.939, 4.265 and 4.507 wt.%, respectively. The hydrogenation saturation ratio of composite containing MoS2 is higher than that of the composites containing CoS and CoS2. The dehydrogenation activation energy of the composites containing CoS, CoS2 and MoS2 is 107.76, 68.43 and 63.28 kJ.mol−1.H2. On the improvement of hydrogen storage performance of Mg20Pr1Sm3Y1Ni10 alloy, the catalytic effect of MoS2 sulfide is better than that of CoS2 sulfide, and which is better than CoS sulfide.