Structure, thermal analysis and dehydriding kinetic properties of Na1−xLixMgH3 hydrides

• NaMgH3 and Li0.5Na0.5MgH3 have been synthesized by ball milling.
• Two decomposition steps have been detected for NaMgH3.
• In comparison with NaMgH3, Li0.5Na0.5MgH3 hydride has better kinetic properties.
• As for LiMgH3, LiH is a good catalyst for the dehydrogenation process.

NaMgH3 hydride with perovskite structure has been synthesized by high-energy ball milling, the maximum hydrogen-desorbed amount of which is 3.42 wt.% at 638 K. Two decomposition steps have been detected for perovskite-type NaMgH3 hydride, calculated values of activation energy for the two steps are 180.25 ± 8.25 kJ/mol and 156.23 ± 18.54 kJ/mol by Kissinger method. In comparison with NaMgH3 hydride, Li0.5Na0.5MgH3 hydride has better dehydriding kinetic properties and higher hydrogen-desorbed amount (4.11 wt.%) due to partial replacement of Na by Li. LiMgH3 hydride with perovskite structure cannot be synthesized by milling of the mixture of LiH and MgH2 hydrides. However, the maximum hydrogen-desorbed amount of this milled mixture is 5.54 wt.% at 638 K, this may suggest that LiH is a good catalyst for dehydrogenation of MgH2, but further research is needed.