Hydrogen-Stabilized ScYNdGd Medium-Entropy Alloy for Hydrogen Storage.

Area of Science:

• Materials Science
• Hydrogen Economy
• Alloy Development

Background:

• Medium- and high-entropy alloys (MEAs and HEAs) are crucial for hydrogen-based technologies.
• Current research focuses on transition-metal-based alloys, neglecting rare-earth-element (REE) systems and specific crystal structures.
• There's a need for novel materials for efficient hydrogen storage and utilization.

Purpose of the Study:

• To investigate the hydrogenation and hydrogen storage properties of a rare-earth-element-based MEA (ScYNdGd).
• To explore the formation of stable crystal structures upon hydrogen absorption in REE-based alloys.
• To evaluate the hydrogen storage capacity and activation behavior of the novel alloy.

Main Methods:

• Synthesis and characterization of a REE-based MEA (ScYNdGd).
• Hydrogenation experiments under mild conditions.
• Analysis of structural changes using X-ray diffraction.
• Measurement of hydrogen storage capacity and desorption kinetics.

Main Results:

• The ScYNdGd MEA stabilized a single-phase face-centered-cubic (FCC) structure upon hydrogenation.
• An unprecedented hydrogen storage capacity of 2.5 H/M was achieved without phase transformation.
• The alloy exhibited facile activation even after prolonged passivation.
• Hydrogen desorption occurred in two distinct steps, originating from octahedral and tetrahedral interstitial sites.

Conclusions:

• REE-based MEAs, particularly those with FCC structures, show significant promise for hydrogen storage applications.
• The stabilization of the FCC phase and high storage capacity highlight the potential of this novel class of materials.
• These findings open new avenues for designing advanced REE-based MEAs and HEAs for the hydrogen economy.