Hydrogen is poised to become a cornerstone of future clean energy systems, yet efficient and safe storage remains a significant challenge. Solid-state hydrogen storage, which involves hydrogen absorption into metals, offers a promising alternative to traditional high-pressure tanks. A new study led by Distinguished Professor Hao Li from Tohoku University reveals that controlling magnetism in hydrogen-storage alloys may provide a solution to the longstanding trade-off between storage capacity and material stability.
The research, published in the journal Chemistry of Materials, identifies magnetism as a previously underestimated factor in the performance of hydrogen-storage materials. Li stated, “Magnetism is usually not considered a central factor in hydrogen storage materials. Our results show that magnetic interactions can decisively determine whether an alloy is stable or unstable.” By manipulating these magnetic properties, the team aims to design alloys that not only maintain thermodynamic stability but can also store substantial amounts of hydrogen.
Exploring AB3-Type Alloys
The researchers focused on a specific class of materials known as AB3-type intermetallic alloys, recognized for their rapid hydrogen absorption and good reversibility. They conducted advanced first-principles calculations alongside Monte Carlo simulations to analyze alloys made from calcium, yttrium, and magnesium at the A-site, with cobalt or nickel at the B-site. Their findings established a clear connection between the strength of magnetism and the stability of these alloys.
In cobalt-based alloys, strong magnetic properties significantly increase the formation energy, leading to thermodynamic instability. While the introduction of lightweight elements like magnesium enhances hydrogen storage capacity, it simultaneously intensifies magnetic interactions, restricting overall performance. To mitigate this issue, the team found that incorporating heavier elements, such as yttrium, could suppress magnetism, though this approach also diminishes hydrogen storage efficiency.
The breakthrough came when the researchers proposed a simple adjustment: replacing cobalt with nickel. Nickel-based alloys exhibit far weaker magnetic properties, and in some configurations, they are nearly non-magnetic. This suppression of magnetism stabilizes the alloy across a broader range of compositions, including magnesium-rich variants that promise high hydrogen storage capacity.
Li elaborated, “By replacing cobalt with nickel, we found that the alloys become much more stable, even when they contain large amounts of magnesium. This allows us to design materials that combine high hydrogen capacity with good thermodynamic stability, which is essential for practical applications.”
Promising Future for Hydrogen Storage
The study highlights the outstanding performance of the well-known hydrogen-storage alloy CaMg2Ni9 and predicts that unexplored magnesium-rich nickel-based alloys could potentially achieve hydrogen capacities of approximately 3.4 weight percent while maintaining thermodynamic stability. This discovery opens avenues for a new class of materials that could be synthesized and experimentally tested.
Beyond identifying specific high-performance alloys, the research establishes magnetism as a crucial design parameter for hydrogen storage materials. It challenges the conventional perspective of magnetic effects as secondary properties, demonstrating that these interactions can significantly influence both alloy stability and hydrogen capacity.
The implications of this research extend beyond hydrogen energy applications. Similar magnetic and electronic effects are also important in the fields of battery technology, catalysis, and other functional materials. By showing how magnetism can be intentionally adjusted to enhance material performance, this study provides a fresh framework for the development of advanced materials across various energy-related domains.
This innovative approach underscores the importance of interdisciplinary research in tackling energy challenges and paves the way for future advancements in hydrogen storage technology.
