HSINCHU, Taiwan, Nov. 20, 2024 — In a groundbreaking advance for materials science, researchers at National Tsing Hua University (NTHU) have created the world's first comprehensive database of high-entropy alloy nanocrystals, paving the way for innovative applications in various fields, such as renewable energy and advanced manufacturing.

High-entropy alloy nanocrystals, known for their diverse metal blends, have emerged as a game-changer in materials research. However, until now, determining the ideal mix of elements and achieving consistent uniformity posed major challenges. The NTHU research team, led by Associate Professor Tung-Han Yang from the Department of Chemical Engineering, has harnessed a method called "dropwise addition" to master crystal growth, making it a crucial step towards unlocking new high-entropy materials.

The concept of high-entropy alloys was introduced by Professor JW Yeh of NTHU in 2004, initiating a global wave of research into these unique materials, which consist of five or more different metals mixed at the atomic level. This high level of disorder gives these alloys superior mechanical properties and exceptional resistance to wear and corrosion. "Combining metals is as intricate as determining familial blood relations in a DNA test," Yang emphasized, highlighting the complexity involved in crafting these alloys.

One of the standout features of Yang’s research is the advancement to the nanometer scale. With enhanced surface areas and superior catalytic properties, high-entropy nanocrystals can potentially foster an endless array of combinations. However, optimizing their elemental compositions has proved to be a Herculean task. Yang's team took inspiration from nature, likening their innovative technique to the growth of cultured pearls, wherein a core is meticulously enveloped by layers of nacre.

"Using this dropwise addition method, we can achieve remarkable control over the arrangement of metal atoms," Yang pointed out. When starting with a palladium crystal core, the team experimented by gradually adding a mixture of liquefied metal ions—iron, cobalt, nickel, rhodium, and others—allowing for the unique crystal structures to emerge. This control has led to the development of nanocrystals organized into honeycomb or square arrays, as well as more complex shapes like pyramids and cubes.

In a light-hearted nod to their research process, the team humorously likened their methodology to coaxing picky cats to eat dry food by coating it with their preferred canned version, symbolizing the adjustments they had to make to ensure optimal crystal formation.

Furthermore, the NTHU team conducted thorough analyses using advanced techniques at the National Synchrotron Radiation Research Center to verify the even stacking of metal atoms. Their findings indicated that utilizing these catalysts for hydrolysis can double efficiency in hydrogen production—an exciting prospect for renewable energy development and achieving net-zero emissions.

With their groundbreaking methods, the team has not only established the first-ever database of high-entropy nanocrystals—complete with control over crystallographic planes—but has also made significant strides towards sustainable technologies. This groundbreaking work has been showcased for two consecutive years in *Science Advances*, and Assistant Professor Kun-Han Lin played a critical role by leading simulations to identify optimal metal compositions and predict material properties.

Lin underscored the significance of their theoretical model, which, while not exhaustive, aligns with their empirical findings. "This is just the beginning. With continued collaboration, we're confident in achieving even greater efficiencies in our research," he added.

As the field of nanocrystals continues to evolve, NTHU stands at the forefront, opening doors to potentially transformative materials that could reshape industries. Stay tuned as we watch these developments unfold!