Thermodynamic destabilization and kinetic optimization for the de-/hydrogenation of Mg85Ni15 alloy by tailoring Mg(In) and Mg2Ni(In) double solid solution

To increase the hydrogen de-/absorption rate and reduce the stability of MgH2, element indium (In) is introduced into the hypereutectic Mg85Ni15 alloy. The results show that solid solution phases of Mg(In) and Mg2Ni(In) are formed simultaneously, and the lattice parameters of Mg crystals decrease while that of Mg2Ni crystals increase. The hydrogen storage capacity of Mg85Ni14.5In0.5 alloy reaches 3.5 wt% at 125 degrees C with the hydrogenation rates accelerated significantly, which is higher than the 2.4 wt% of Mg85Ni15 alloy. For dehydrogenation, Mg85Ni14In1.0 hydride can release 4.1 wt% hydrogen at 225 degrees C in 15 min. The main peak temperature in DSC test for dehydrogenation is decreased to 226.6 degrees C of Mg85Ni13.5In1.5 hydride from 246.1 degrees C of Mg85Ni15 hydride and decomposition enthalpy (Delta H) of Mg85Ni13.5In1.5 hydride is decreased to 60.9 kJ/mol. The rapid hydrogenation rate is owing to the dissolved In atoms in Mg2Ni lattice causing lattice expansion, which acts as fast diffusion path for hydrogen atoms. In Mg(In)H2 phase, the strong interaction between Mg and In weakens the affinity of Mg and H, which accounts for the reduced Delta H of Mg(In)H2. The weakened strength of Ni-H bond in Mg2Ni(In)H4 also results in the decreased stability of hydride. (c) 2023 Elsevier B.V. All rights reserved.

Automated summary

In element is introduced into Mg85Ni15 alloy to increase the hydrogen de-/absorption rate of MgH2. The addition of In forms Mg(In) and Mg2Ni(In) solid solution phases, resulting in both decreasing lattice parameters of Mg and increasing lattice parameters of Mg2Ni crystals. The introduction of In significantly accelerates the hydrogenation rate, with Mg85Ni14.5In0.5 alloy reaching a hydrogen storage capacity of 3.5 wt% at 125 degrees C, higher than that of Mg85Ni15 alloy. For dehydrogenation, Mg85Ni14In1.0 hydride can release 4.1 wt% hydrogen at 225 degrees C in 15 min. The presence of In weakens the affinity of Mg and H in Mg(In)H2 phase and decreases the stability of hydride in Mg2Ni(In)H4 phase.