A research team led by Dr. Kee Young Koo from the Hydrogen Research Department at the Korea Institute of Energy Research (President: Yi Chang-Keun, hereafter referred to as KIER) has developed a novel and more cost-effective method for synthesizing ammonia decomposition catalysts. This new approach enables more efficient hydrogen production from ammonia and is expected to make a significant contribution to the realization of a hydrogen economy.
Composed of three hydrogen atoms and one nitrogen atom, ammonia has a high hydrogen content, making it a promising hydrogen carrier for long-distance transport and large-scale storage. With global infrastructure for its transport and storage already in place, ammonia offers a more economical means of hydrogen delivery compared to other carriers. However, the technology for decomposing ammonia to produce hydrogen at the point of demand is still in the early stages of development.
The core of this technology lies in the use of ruthenium (Ru) catalysts. Ruthenium enables rapid ammonia decomposition at lower temperatures—between 500°C and 600°C—which is over 100°C lower than that required by other catalysts. The challenge, however, is that ruthenium is an extremely rare metal found in only a few countries, making it difficult to procure.
Until now, ruthenium has been used in nanoscale form to maximize performance even in small quantities. However, the large-scale production of nanocatalysts involves complex processes and high manufacturing costs, which hinder the commercialization of ammonia decomposition technology.
In response, the research team developed a novel ruthenium catalyst synthesis method based on the polyol process, aimed at improving the economic viability of the catalyst. The catalyst produced through this method demonstrated more than three times higher ammonia decomposition performance compared to conventional catalysts.
The polyol* process applied by the research team is commonly used to synthesize metals into nanoparticles. In conventional processes, capping agents are added to prevent the particles from clumping together, but this makes the process more complex and increases costs. To address this, the team devised a method to control nanoparticle aggregation without the use of capping agents.
* Polyol: A viscous, sticky liquid alcohol containing multiple –OH (hydroxyl) groups, commonly used in processes that reduce metals into nanoparticles. Representative examples include ethylene glycol, glycerol, and butylene glycol. |
The research team focused on the fact that the length of organic molecules known as carbon chains affects the degree of particle aggregation. They hypothesized that by controlling the structure and length of these carbon chains, nanoparticle aggregation could be effectively suppressed without the need for additives.
* Carbon chain: A structure in which carbon atoms are bonded together; its length varies depending on the number of carbon atoms contained in the molecule. |
Through experiments, the research team confirmed that using butylene glycol, which has a long carbon chain, allowed 2.5nm sized ruthenium particles to be uniformly dispersed without the need for capping agents. They also verified the formation of 'B5 sites'*—the active sites where hydrogen production reactions occur.
* B5 site: A highly reactive structural site where three ruthenium atoms are positioned on a stepped surface, with two additional atoms located on the terrace edge above them, facilitating enhanced catalytic activity. |
The resulting catalyst significantly outperformed existing catalysts. Compared to conventional ruthenium catalysts that did not use butylene glycol, the activation energy* was reduced by approximately 20%, and the hydrogen formation rate increased by 1.7 times. Furthermore, when comparing ammonia decomposition performance per unit volume, the catalyst demonstrated more than three times higher efficiency than those produced using conventional synthesis methods, highlighting its excellent economic potential.**
* Activation energy: The minimum amount of energy required for a chemical reaction to occur, expressed in kJ·mol⁻¹ (kilojoules needed per mole of molecules for the hydrogen production reaction). The catalyst developed by the research team showed an activation energy of 49.8 kJ·mol⁻¹. ** Hydrogen formation rate: In this study, it is measured in mmolH₂·gcat⁻¹·h⁻¹, which indicates the amount of hydrogen produced per gram of catalyst per hour. The catalyst developed by the research team achieved a hydrogen formation rate of 1,236 mmolH₂·gcat⁻¹·h⁻¹. |
Dr. Kee Young Koo, the lead researcher, stated, "The ammonia decomposition catalyst synthesis technology developed in this study is a practical solution to overcome the limitations and cost issues associated with mass production of conventional nanocatalysts. It is expected to contribute to the localization and commercialization of ammonia decomposition catalyst technology." She added, "We plan to move forward with performance verification through mass production of pellet-type catalysts and application in various ammonia cracking systems."
This achievement was published as a cover paper in Small (Impact Factor 12.1), a prestigious journal in the field of nanotechnology, and was carried out with support from the Global Top Strategic Research Program of the National Research Council of Science & Technology, under the Ministry of Science and ICT.
* Paper Information: https://doi.org/10.1002/smll.202407338 (Published on April 23, 2025 / Selected for the Inside Front Cover) |
