A joint research team led by Kim Hyun-jung, Professor of the Department of Physics, Identifies a New Pathway Through Which Internal Crystal Defects (Dislocations) Transport Ruthenium Catalysts to the Surface
A joint research team led by Kim Hyun-jung, Professor of the Department of Physics at this university (including Dr. Choi Seong-Wook, currently at Samsung Electronics) has uncovered the mechanism by which costly ruthenium catalyst nanoparticles form on oxide surfaces. They discovered that “dislocations”—defects that originate inside the crystal and grow toward the surface—directly carry ruthenium metal atoms to the surface.
As the era of artificial intelligence (AI) dawns and electricity demand skyrockets, eco-friendly technologies for the production and utilization of hydrogen and ammonia are emerging as solutions for a stable energy supply. While precious metal catalysts such as platinum and ruthenium are essential for eco-friendly technologies like fuel cells and hydrogen production, their usage has been limited by their high cost and poor durability. To address this, “exsolution” technology, which involves pre-embedding metal atoms within an oxide crystal and then allowing them to migrate to the surface on their own to become firmly embedded, has garnered attention as an alternative. Ruthenium, in particular, is a key catalyst in ammonia energy systems. However, the fundamental mechanism by which metal atoms traverse the depths of the crystal to reach the surface had remained a mystery until now.
Using ruthenium-doped perovskite oxide particles as a model, the research team observed this process by combining “Bragg Coherent Diffraction Imaging (BCDI)” with “transmission electron microscopy (TEM).” BCDI is a technique that uses phase-matched X-rays to visualize minute distortions within nanocrystals as three-dimensional images, while TEM is a technique that examines a material’s composition and defect structure at the atomic level. The observations revealed that before the metal emerged at the surface, a linear defect called a “dislocation” first formed inside the crystal and grew toward the surface; in particular, approximately 75% of the surface particles were concentrated at the tips of “mixed-type dislocations.” The most significant finding is that these mixed-type dislocations are not static defects, but rather act as “carriers” that transport ruthenium atoms toward the surface as they grow. This study has demonstrated that catalytic particles are not formed randomly on the surface, but are created in close association with defects within the material.
Previously, metal atoms had to travel across the entire crystal, requiring a long time at high temperatures, however, this study revealed that as the dislocation grows, it takes over the task of atom transport, effectively providing the atoms with a sort of “shortcut.” Professor Kim stated, “We confirmed that the size and distribution of catalytic particles can be precisely engineered depending on the type of defect created,” adding, “This achievement will contribute to the development of the ammonia-based hydrogen energy value chain and highly durable catalysts.”
This research was conducted jointly by Professor Kim’s research team at this university and the research teams led by Drs. Ji Ho-il and Kwon Deok-hwang at KIST (Korea Institute of Science and Technology). Dr. Choi Seong-wook from this university and Dr. Lim Young-hwan from KIST served as co-first authors. The research was supported by the Leader Research Support Program, a joint initiative of the Ministry of Science and ICT and the National Research Foundation of Korea, and the findings were published in the international academic journal Nature Communications.
▶ Paper Title: Dynamics of Dislocation Formations and Their Impacts on Exsolution in Ru-Doped Perovskite Oxide (DOI: 10.1038/s41467-026-73457-7)
[SEO Keyword]
Exsolution, Dislocation, Ruthenium catalyst
As the era of artificial intelligence (AI) dawns and electricity demand skyrockets, eco-friendly technologies for the production and utilization of hydrogen and ammonia are emerging as solutions for a stable energy supply. While precious metal catalysts such as platinum and ruthenium are essential for eco-friendly technologies like fuel cells and hydrogen production, their usage has been limited by their high cost and poor durability. To address this, “exsolution” technology, which involves pre-embedding metal atoms within an oxide crystal and then allowing them to migrate to the surface on their own to become firmly embedded, has garnered attention as an alternative. Ruthenium, in particular, is a key catalyst in ammonia energy systems. However, the fundamental mechanism by which metal atoms traverse the depths of the crystal to reach the surface had remained a mystery until now.
Using ruthenium-doped perovskite oxide particles as a model, the research team observed this process by combining “Bragg Coherent Diffraction Imaging (BCDI)” with “transmission electron microscopy (TEM).” BCDI is a technique that uses phase-matched X-rays to visualize minute distortions within nanocrystals as three-dimensional images, while TEM is a technique that examines a material’s composition and defect structure at the atomic level. The observations revealed that before the metal emerged at the surface, a linear defect called a “dislocation” first formed inside the crystal and grew toward the surface; in particular, approximately 75% of the surface particles were concentrated at the tips of “mixed-type dislocations.” The most significant finding is that these mixed-type dislocations are not static defects, but rather act as “carriers” that transport ruthenium atoms toward the surface as they grow. This study has demonstrated that catalytic particles are not formed randomly on the surface, but are created in close association with defects within the material.
Previously, metal atoms had to travel across the entire crystal, requiring a long time at high temperatures, however, this study revealed that as the dislocation grows, it takes over the task of atom transport, effectively providing the atoms with a sort of “shortcut.” Professor Kim stated, “We confirmed that the size and distribution of catalytic particles can be precisely engineered depending on the type of defect created,” adding, “This achievement will contribute to the development of the ammonia-based hydrogen energy value chain and highly durable catalysts.”
This research was conducted jointly by Professor Kim’s research team at this university and the research teams led by Drs. Ji Ho-il and Kwon Deok-hwang at KIST (Korea Institute of Science and Technology). Dr. Choi Seong-wook from this university and Dr. Lim Young-hwan from KIST served as co-first authors. The research was supported by the Leader Research Support Program, a joint initiative of the Ministry of Science and ICT and the National Research Foundation of Korea, and the findings were published in the international academic journal Nature Communications.
▶ Paper Title: Dynamics of Dislocation Formations and Their Impacts on Exsolution in Ru-Doped Perovskite Oxide (DOI: 10.1038/s41467-026-73457-7)
[SEO Keyword]
Exsolution, Dislocation, Ruthenium catalyst