Hydrogen storage performances of LaMg11Ni + x wt% Ni (x = 100, 200) alloys prepared by mechanical milling

Abstract

In order to improve the hydrogen storage performances of Mg-based materials, LaMg11Ni alloy was prepared by vacuum induction melting. Then the nanocrystalline/amorphous LaMg11Ni+xwt% Ni (x=100, 200) hydrogen storage alloys were synthesized by ball milling technology. The structure characterizations of the alloys were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage characteristics were tested by using programmed control battery testing system. The electrochemical impedance spectra (EIS), potentiodynamic polarization curves and potential-step curves were also plotted by an electrochemical workstation (PARSTAT 2273). The results indicate that the as-milled alloys exhibit a nanocrystalline and amorphous structure, and the amorphization degree of the alloys visibly increases with extending milling time. Prolonging the milling duration markedly enhances the electrochemical discharge capacity and cyclic stability of the alloys. The electrochemical kinetics, including high rate discharge ability (HRD), charge transfer rate, limiting current density (IL), hydrogen diffusion coefficient (D), monotonously decrease with milling time prolonging.