In Situ Embedding of Mg2NiH4 and YH3 Nanoparticles into Bimetallic Hydride NaMgH3 to Inhibit Phase Segregation for Enhanced Hydrogen Storage

For the first time, component segregation during cycling was demonstrated to be responsible for the deterioration in the kinetics of bimetallic hydride NaMgH3. To solve this problem, we propose a method involving in situ embedding of Mg2NiH4 and YH3 into NaMgH3, which is accomplished with a solid-phase reaction using amorphous Mg12YNi alloy and NaH as starting materials under a H-2 atmosphere. Using this novel method, 12 wt % of the Mg2NiH4 phase and 11 wt % of the YH3 phase were homogeneously embedded in the NaMgH3 matrix. In comparison to those of pure NaMgH3, this composite material exhibits no change in thermodynamics but shows greatly enhanced kinetics for hydrogen absorption and desorption cycling. In addition, reasonable mechanisms for the enhanced kinetics have been proposed including the prevention of macroscopic segregation of metallic Na, grain refinement, and a synergistic catalytic effect. All of these mechanisms rely on the intimately interdispersed Mg2NiH4 and YH3 nanoparticles embedded in the NaMgH3 matrix.