"Ammonia Decomposition Performance Tripled" Korea Institute of Energy Research Develops Novel Catalyst Synthesis Method

A new catalyst synthesis method has been developed that enables more efficient decomposition of hydrogen from ammonia. Ammonia consists of three hydrogen atoms and one nitrogen atom. Due to its high hydrogen content, it is gaining attention as a hydrogen carrier suitable for long-distance transport and large-scale storage. Ammonia is considered more economical than other hydrogen carriers because of its well-established global infrastructure for transport and storage. However, the technology to decompose ammonia and produce hydrogen at the point of demand is still in the early stages of development.

On July 3, the Korea Institute of Energy Research announced that a research team led by Dr. Kiyoung Koo from the Hydrogen Research Division has developed a novel ammonia decomposition catalyst synthesis method with three times the performance of existing methods.

(From left) Dr. Woongho Jung, Dr. Kiyoung Koo, Dr. Byungseon Ahn, Dr. Yongha Park. Courtesy of Korea Institute of Energy Research

The key to the technology developed by the research team is the use of a ruthenium (Ru) catalyst. Ruthenium enables rapid decomposition of ammonia at 500 to 600 degrees Celsius, which is more than 100 degrees lower than the temperatures required by other catalysts.

However, ruthenium is an extremely rare metal found in only a few countries, making it challenging to use as a catalyst. To address this, ruthenium has so far been utilized in nanoscale form to achieve high performance with minimal quantities. Nevertheless, the mass production process for nano-catalysts is complex and costly, posing limitations to the commercialization of ammonia decomposition technology.

To solve these issues, the research team developed a novel ruthenium catalyst synthesis method based on the polyol process, thereby improving the economic feasibility of the catalyst. In fact, catalysts produced using this new synthesis method demonstrated ammonia decomposition performance more than three times higher than conventional catalysts.

The polyol process applied by the research team is mainly used to synthesize metals into nanoparticles. In conventional processes, stabilizers are added to prevent particle agglomeration, but this increases process complexity and costs.

To overcome this, the team devised a method to control nanoparticle agglomeration without using stabilizers. They focused on the fact that the length of organic molecules called carbon chains (structures in which carbon atoms are connected) affects the degree of particle agglomeration. By adjusting the structure and length of the carbon chains, they were able to effectively suppress nanoparticle agglomeration without additional additives.

Experiments confirmed that when long-chain butylene glycol was used, ruthenium particles with a uniform size of 2.5 nm were dispersed without stabilizers, and 'B5 sites' (a structure where three ruthenium atoms are positioned on a stepped surface and two atoms are located at the terrace edge) necessary for hydrogen generation were formed.

As a result, the catalyst produced using this method showed a 20% reduction in activation energy and a 1.7-fold increase in hydrogen generation rate compared to conventional ruthenium catalysts without butylene glycol. Furthermore, when comparing ammonia decomposition performance per unit volume, the new catalyst exhibited performance more than three times higher than catalysts produced by existing synthesis methods, making economic feasibility achievable.

Dr. Kiyoung Koo stated, "The ammonia decomposition catalyst synthesis technology we have developed is a practical solution to the limitations and cost issues of mass-producing conventional nano-catalysts," adding, "We expect it will contribute to the localization and commercialization of ammonia decomposition catalyst technology in the future."

This research was supported by the Global TOP Strategic Research Group Program of the National Research Council of Science and Technology under the Ministry of Science and ICT. The results were published as a cover paper in the renowned nanoscience journal 'Small.'