Gaseous and electrochemical hydrogen storage kinetics of nanocrystalline Mg2Ni-type alloy prepared by rapid quenching

The nanocrystalline Mg2Ni-type Mg2Ni1−xCux (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by direct melt quenching technique. The structures of the as-cast and quenched alloys were investigated by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the alloys was tested by using constant current to charge and discharge the electrode. The results indicate that the substitution of Cu notably rendered the grain refinement of the as-cast alloys without altering the major phase Mg2Ni. All the as-quenched alloys exhibit a nanocrystalline structure without the presence of any amorphous phase. It is found that the substitution of Cu for Ni and rapid quenching significantly ameliorated the gaseous and electrochemical hydrogen storage kinetics of the nanocrystalline Mg2Ni1−xCux (x = 0–0.4) alloys. Furthermore, both the rapid quenching treatment and the Cu substitution results in a notable increase in the hydrogen diffusion coefficient (D) as well as the limiting current density (IL) but an obvious decline in the electrochemical impedance.

► The nanocrystralline and amorphous Mg2Ni-type Mg2Ni1−xCux (x = 0–0.4) alloys are fabricated by melt-spinning technique.
► All the as-quenched Mg2Ni1−xCux (x = 0, 0.1, 0.2, 0.3, 0.4) alloys hold an entire nanocrystalline structure and are free of amorphous phase.
► The rapid quenching leads to an evident reduction of the grain sizes of the alloys.
► The rapid quenching significantly improves the gaseous and elctrochemical hydrogen storage kinetics of the alloys.