The electrochemical hydrogen storage characteristics of as-spun nanocrystalline and amorphous Mg20Ni10−x M x (M=Cu, Co, Mn; x = 0–4) alloys

Abstract

In this paper, we comprehensively investigate the influences of M (M=Cu, Co, Mn) substitution for Ni on the structures and electrochemical hydrogen storage characteristics of the nanocrystalline and amorphous Mg20Ni10−x M x (M=Cu, Co, Mn; x = 0–4) alloys prepared by melt spinning. The as-spun (M=None, Cu) alloys display an entire nanocrystalline structure, whereas the as-spun (M=Co, Mn) alloys hold a mixed structure of both nanocrystalline and amorphous when x = 4 (M content). These results indicate that the substitution of M (M=Co, Mn) for Ni facilitates the glass formation in Mg2Ni-type alloy. All the as-spun alloys have the Mg2Ni major phase, but M (M=Co, Mn) substitution brings on some secondary phases, such as MgCo2, Mg phases for M=Co, and MnNi, Mg phases for M=Mn. The substitution of M (M=Cu, Co, Mn) for Ni also makes a positive contribution to the cycle stability of the alloys in the following orders: (M=Cu) > (M=Co) > (M=Mn) for x = 1 and (M=Co) > (M=Mn) > (M=Cu) for x = 2–4. Meanwhile, it notably enhances the discharge capacity of the alloys in the sequence of (M=Co) > (M=Mn) > (M=Cu). As for the high rate discharge ability, it visibly upgrades with the growing of M content for (M=Cu, Co), while it grows at first and then declines for (M=Mn).