Researchers at the University of Queensland have show that a low-cost Mg-based hydrogen storage alloy is possible with only 1 wt% Si. A high hydrogen capacity of 6.72 wt% hydrogen is achieved via trace sodium (Na) addition. A paper on their work is published in the Journal of Power Sources.

Mg₂Si is a promising catalyst for Mg-based hydrogen storage materials due to its low cost, light weight, and non-toxic properties. The researchers investigated the effects of Na in hypo-eutectic Mg-1wt.%Si alloys for hydrogen storage applications.

They found that the addition of trace amounts of Na is vital in improving the hydrogen sorption kinetics, achieving a H₂ storage capacity of 6.72 wt.% at 350 °C under 2 MPa, compared to 0.31 wt.% in the non-Na added alloy.

Analysis showed that Na affects the surface of the Mg alloys, forming porous Na₂O and NaOH in addition to MgO, facilitating the diffusion of hydrogen. In-situ synchrotron powder X-ray diffraction showed the resulting Mg₂Si catalyst is stable during the H₂ sorption reactions.

This result demonstrates the potential use of Mg–Mg₂Si casting alloys for large scale hydrogen storage and transportation applications.

—Tan et al.

Resources

• Xin F. Tan, Manjin Kim, Qinfen Gu, Julio Pinzon Piraquive, Guang Zeng, Stuart D. McDonald, Kazuhiro Nogita (2022) “Na-modified cast hypo-eutectic Mg–Mg2Si alloys for solid-state hydrogen storage,” Journal of Power Sources, Volume 538 doi: 10.1016/j.jpowsour.2022.231538