Temperature-dependent hydrogenation behaviour and hydrogen storage thermodynamics of Mg_0.9In_0.1 solid solution alloy

To clarify the hydrogen storage mechanism of Mg(In) solid solution, the hydrogenation and dehydrogenation characteristics of Mg_0.9In_0.1 alloy are systematically studied in this work. It is found that the Mg_0.9In_0.1 solid solution is first hydrogenated to Mg₃In and MgH₂ under a hydrogen atmosphere. The polymorphism of Mg₃In leads to different hydrogenation features of the solid solution in various temperature ranges. Consequently, the reversible dehydrogenation reactions have somewhat distinct enthalpy changes due to the different crystal structures of Mg₃In. When the hydrogenation temperature is not lower than 340 °C, Mg₃In can be further hydrogenated to (Mg_1-In)₃In and MgH₂. The hydrogenation reactions of both β'-Mg₃In and β-Mg₃In are also reversible although they have sloping hydrogenation and dehydrogenation plateaus in pressure-composition isotherms. This work provides new insights into the hydrogen storage mechanism of Mg(In) solid solution.