Improved Physical and Electrochemical Hydrogen Storage Kinetics of the As-Spun Mg<sub>2</sub>Ni-Type Alloys by Substituting Ni with M (M=Co, Cu)

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In order to improve the physical and electrochemical hydrogen storage kinetics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by M (M=Co, Cu). Melt-spinning technology was used for the preparation of the Mg20Ni10-xMx (M=Co, Cu; x=0, 1, 2, 3, 4) hydrogen storage alloys. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The physical and electrochemical hydrogen storage kinetics of the alloys is measured. The results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, whereas the as-spun (M=Co) alloys exhibit a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of M (M=Co, Cu) for Ni engenders an insignificant effect on the hydrogen absorption kinetics of the alloys, but it markedly ameliorates the hydrogen desorption kinetics of the alloys and the high rate discharge ability. With an increase of the M (M=Co, Cu) content from 0 to 4, the hydrogen desorption ratio ( ) is enhanced form 20.0% to 65.43% for the as-spun (20 m/s) alloy (M=Co), and from 20.0% to 52.88% for the as-spun (20 m/s) alloy (M=Cu).