Gaseous and Electrochemical Hydrogen Storage Properties of Nanocrystalline Mg₂Ni-Type Alloys Prepared by Melt Spinning

Abstract

A partial substitution of Ni by Cu has been carried out in order to improve the hydrogen storage characteristics of the Mg₂Ni-type alloys. The nanocrystalline Mg₂₀Ni_10-xCu_x (x = 0, 1, 2, 3, 4) alloys are synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The electrochemical performances were evaluated by an automatic galvanostatic system. The hydrogen absorption and desorption kinetics of the alloys were determined by using an automatically controlled Sieverts apparatus. The results indicate that the substitution of Cu for Ni does not alter the major phase Mg₂Ni. The Cu substitution significantly ameliorates the electrochemical hydrogen storage performances of alloys, involving both the discharge capacity and the cycle stability. The hydrogen absorption capacity of alloys has been observed to be first increase and then decrease with an increase in the Cu contents. However, the hydrogen desorption capacity of the alloys exhibit a monotonous growth with an increase in the Cu contents.