Reversible De/hydriding Reactions between Two New Mg–In–Ni Compounds with Improved Thermodynamics and Kinetics

Magnesium-based alloys show great potential for hydrogen storage because of their high capacity, excellent reversibility, and low cost. However, the sluggish hydrogen sorption kinetics and overhigh dehydrogenation temperature hinder their practical application. In this paper, we present the reversible de/hydriding reaction mechanism of two new Mg–In–Ni ternary intermetallic compounds, which shows improved thermodynamics and kinetics in comparison with pure Mg. These two new phases correspond to Mg 2 InNi and Mg 14 In 3 Ni 3 stoichiometries, both with orthorhombic structure, as determined by combinational X-ray diffraction and electron diffraction tomography analysis. In the hydriding process, the Mg 14 In 3 Ni 3 alloy decomposes into a mixture of MgH 2 and Mg 2 InNi, which is fully reversible in the dehydrogenation with hydrogen storage capacity of 1.8 wt %. For the dehydriding of MgH 2 and Mg 2 InNi, a decrease of the reaction enthalpy (70.1 kJ mol –1 H 2 ) is obtained compared with pure MgH 2 (72.2 kJ mol –1 H 2 ), and the dehydrogenation activation energy is decreased to 78.5 kJ mol –1 from ∼160 kJ mol –1 for pure MgH 2 . Comparatively, the alloy Mg 90 In 5 Ni 5 containing the Mg 14 In 3 Ni 3 phase has higher reversible hydrogen storage capacity of 3.3 wt %, and the minimum dehydrogenation temperature is reduced to 220 °C. This work demonstrates the potential of exploring new Mg-based intermetallic compounds for hydrogen storage applications.