Dual-tuning effects of In, Al, and Ti on the thermodynamics and kinetics of Mg₈₅In₅Al₅Ti₅ alloy synthesized by plasma milling

Highlights: • Mg₈₅In₅Al₅Ti₅ alloy catalyzed with in-situ formed MgF₂ was prepared by P-milling. • Reaction mechanism of Mg₈₅In₅Al₅Ti₅ alloy was presented. • Further destabilization of Mg was realized (65.2 kJ/mol H₂). • Dual tuning of the thermodynamic and kinetic properties of MgH₂ was realized. - Abstract: The dehydrogenation enthalpy change of MgH₂ by reversibly forming an Mg_0.95In_0.05 solid solution offers a new method for tuning the thermodynamics of Mg-based alloys. In order to further lower the stability of MgH₂, Al has been introduced into Mg(In) solid solution. At the same time, to solve the problem of sluggish kinetic properties of Mg–In solid–solution systems and to lower the dehydrogenation activation energy, Ti has also been added. It has been demonstrated that the Mg₈₅In₅Al₅Ti₅ alloy synthesized by plasma milling (P-milling) shows both enhanced dehydriding thermodynamics and kinetics. This technique could be used to synthesize Mg(In, Al) ternary solid solution incorporating the Ti catalyst in only one step, making it much more efficient than the two-step method. Compared with Mg-based solid solutions, the addition of Ti and in-situ synthesized MgF₂ improved the kinetics and the introduction of In as well as Al imparted enhanced thermodynamics to the Mg₈₅In₅Al₅Ti₅ system. The dehydrogenation enthalpy change and activation energy were lowered to 65.2 kJ/(mol H₂) and 125.2 kJ/mol, respectively, for the Mg₈₅In₅Al₅Ti₅ alloy