An investigation of the electrochemical hydrogen storage performances of the RE-Mg-Ni-based A_2B_7-type electrode alloys prepared by melt spinning

摘要

The RE-Mg-Ni-based A_2B_7-type La_(0.75-x)Pr)_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1) (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys were synthesized by melt spinning technology. The impacts of the melt spinning and the substitution of Pr for La on the microstructures and electrochemical characteristics of the alloys were investigated in detail. The results reveal that the as-cast and spun alloys have a multiphase structure, containing two main phases (La, Mg)_2Ni_7 and LaNi_5 as well as a residual phase LaNi_2. The melt spinning results in a notable grain refinement of the alloys without altering the phase structure of the alloys. The discharge capacity of the (x=0.1) alloy first mounts up and then falls with rising the spinning rate. And the as-spun (10 m/s) alloy yields the maximum discharge capacity with the variation of Pr content. Furthermore, the measurements of the electrochemical hydrogen storage kinetics reveal that the high rate discharge ability (HRD), the hydrogen diffusion coefficient (D) and the limiting current density (I_L) of the alloys first increases then decreases with rising the spinning rate and the amount of Pr substitution.