Microstructure and electrochemical hydrogenation/dehydrogenation performance of melt-spun La-doped Mg₂Ni alloys

This work focuses on microstructure and electrochemical hydrogen storage properties of La-doped Mg₂Ni alloys. The alloys with nominal compositions of Mg₂Ni_{1 - x}La_x (x = 0, 0.1, 0.3, 0.5) were prepared via metallurgical smelting and melt-spun on a rotating copper wheel. The scanning electron microscope, X-ray diffraction, differential scanning calorimetry and transition electron microscope, galvanostatic charging/discharging and other electrochemical measurements were employed to investigate. The results show that the increasing of La content and melt-spinning speed favors the formation of Mg-Ni-La amorphous/nanocrystalline alloys. It is found that the melt-spun ribbons display increased discharge capacities and superior cycle stabilities compared to the as-cast alloys with and without La. The potentiodynamic polarization results indicate that melt-spun La-doped Mg₂Ni ribbons possess more positive corrosion potential E_corr and exhibit relatively high corrosion resistance against the alkaline solution. The mechanism for electrochemical hydrogenation/dehydrogenation has been proposed based on the effect of microstructures on the mass/charge transfer process for electrode electrochemical reaction.