Synthesis and hydriding behavior of Li2MgPt

We describe preparation of the ternary intermetallic Li2MgPt and determination of its crystal structure and hydrogen sorption behavior. Phase formation was suggested by density functional theory calculations. The compound crystallizes in the cubic P4¯3m space group and is isostructural to Li2MgSi and Li2MgIr. Its reaction with hydrogen proceeds according to Li2MgPt + H2 → MgPt + 2LiH, in which MgPt is a new member of the Mg–Pt binary phase diagram.

Research highlights▶ The new phase Li2MgPt can be formed by mechanical milling of the constituent elements. ▶ Li2MgPt crystallizes in the cubic P4¯3m space group and is isostructural to the known phases Li2MgSi and Li2MgIr. ▶ Hydriding of Li2MgPt proceeds according to the reaction Li2MgPt + H2 → MgPt + 2LiH. Tetragonal MgPt is a new member of the Mg–Pt binary phase diagram previously misidentified by others as an Mg–Pt–C–H quaternary. ▶ Li2MgPt can also be formed by heat treating a mixture of LiH and MgPt in a 2:1 ratio. The reaction occurs below the decomposition temperature of LiH, so that MgPt can be considered to destabilize LiH. ▶ Even ignoring the cost of Pt, this system is unsuitable for cyclable hydrogen due to the accumulation of undesirable secondary phases with repeated exposure.