| Abstract |
| The dehydrogenation rates of graphene-added Mg (named Mg-5graphene) were very low at 573 K and 593 K. Ni was added to increase the dehydrogenation rates of graphene-added Mg. Samples (designated as Mg-2.5Ni-2.5graphene) with a composition of 95 wt% Mg + 2.5 wt% Ni + 2.5 wt% graphene were prepared by milling in hydrogen (reactive ball milling). Mg-2.5Ni-2.5graphene had significantly higher initial hydrogenation and dehydrogenation rates and much greater amounts of hydrogen absorbed and released after 60 min, Ha (60 min) and Hd (60 min), than Mg-5graphene. The addition of Ni lowered the magnesium hydride decomposition temperature from 683 K to 581 K. The activation of Mg-2.5Ni-2.5graphene was finished after the second hydrogenation-dehydrogenation cycle (n=2). Mg-2.5Ni-2.5graphene had a very high efficient capacity of stored hydrogen (the amount of hydrogen absorbed after 60 min) higher than 7 wt% (7.07 wt% at 573 K in 12 bar H2 at n=1). At n=1, the quantities of hydrogen released by Mg-2.5Ni-2.5graphene were 0.26 wt% H after 2.5 min and 3.34 wt% H after 60 min at 573K in 1.0 bar H2.
(Received June 28, 2019; Accepted August 20, 2019) |
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| Key Words |
| hydrogen absorbing materials, reactive ball milling, scanning electron microscopy (SEM), X-ray, diffraction, graphene and Ni addition |
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