Hydrogen Storage Properties of Pure MgH2

Abstract

The hydrogen storage properties of pure <TEX>$MgH_2$</TEX> were studied and compared with those of pure Mg. At the first cycle, pure <TEX>$MgH_2$</TEX> absorbed hydrogen very slowly at 573 K under 12 bar <TEX>$H_2$</TEX>. The activation of pure <TEX>$MgH_2$</TEX> was completed after three hydriding-dehydriding cycles. At the <TEX>$4^{th}$</TEX> cycle, the pure <TEX>$MgH_2$</TEX> absorbed 1.55 wt% H for 5 min, 2.04 wt% H for 10 min, and 3.59 wt% H for 60 min, showing that the activated <TEX>$MgH_2$</TEX> had a much higher initial hydriding rate and much larger <TEX>$H_a$</TEX> (60 min), quantity of hydrogen absorbed for 60 min, than did activated pure Mg. The activated pure Mg, whose activation was completed after four hydriding-dehydriding cycles, absorbed 0.80 wt% H for 5 min, 1.25 wt% H for 10 min, and 2.34 wt% H for 60 min. The particle sizes of the <TEX>$MgH_2$</TEX> were much smaller than those of the pure Mg before and after hydriding-dehydriding cycling. The pure Mg had larger hydrogen quantities absorbed at 573K under 12 bar <TEX>$H_2$</TEX> for 60 min, <TEX>$H_a$</TEX> (60 min), than did the pure <TEX>$MgH_2$</TEX> from the number of cycles n = 1 to n = 3; however, the pure <TEX>$MgH_2$</TEX> had larger <TEX>$H_a$</TEX> (60 min) than did the pure Mg from n = 4 to n = 6.