In the quest for clean energy solutions, hydrogen has emerged as a promising energy carrier. However, storing hydrogen efficiently and reversibly remains a significant challenge. A team of researchers from Tohoku University, led by Professor Shin-ichi Orimo, has been exploring ways to optimize hydrogen storage in AB3-type intermetallic alloys. Their recent findings, published in the journal Advanced Energy Materials, shed light on the intricate relationship between magnetism and the stability of these alloys, offering practical insights for the energy sector.
The researchers focused on AB3 compounds, where A represents elements like calcium (Ca), yttrium (Y), or magnesium (Mg), and B stands for cobalt (Co) or nickel (Ni). They also examined ternary alloys, which are combinations of these elements. Using advanced computational methods, including first-principles calculations and Monte Carlo simulations, the team investigated how different compositions affect the alloys’ properties.
The study revealed a direct correlation between the formation energy of these alloys and their total magnetic moment. Formation energy is a measure of the stability of the alloy, while the magnetic moment indicates the strength of its magnetism. The researchers found that in cobalt-rich systems with large lattice volumes, the formation energy increases with magnetization, suggesting that magnetism is the dominant factor influencing stability.
For magnesium-rich compositions, although they achieve high gravimetric densities, strong magnetism tends to destabilize the system. The researchers discovered that substituting yttrium for magnesium can suppress magnetic moments, thereby enhancing stability. Additionally, replacing cobalt with nickel was found to weaken magnetism significantly. Notably, YNi3 was found to be nonmagnetic, while CaNi3 and MgNi3 exhibited only weak polarization. This allowed for thermodynamic stability across various compositions.
One of the most promising findings was the identification of CaMg2Ni9, which combines a high theoretical hydrogen storage capacity of 3.32 weight percent with good reversibility. The researchers also predicted that magnesium-rich nickel-based alloys could offer negative formation energies, indicating enhanced stability, along with the highest gravimetric densities, reaching up to 3.40 weight percent.
The practical implications of this research are significant for the energy industry. By controlling magnetism through transition-metal substitution, it is possible to overcome the trade-off between stability and capacity in hydrogen storage materials. This could lead to the development of more efficient and reversible solid-state hydrogen storage systems, which are crucial for advancing hydrogen as a clean energy carrier.
The researchers’ work highlights the importance of understanding and manipulating magnetic properties to optimize the performance of hydrogen storage materials. As the world continues to seek sustainable energy solutions, these findings offer a promising path forward for the energy sector.
This article is based on research available at arXiv.