<(From left) Professor Lee Hyun-joo, doctoral candidate Choi Yoon-ji, doctoral candidate Han Jae-beom, and Professor Park Jeong-young>

As unprecedented heat waves and cold waves make the climate crisis a part of everyday life, technology to effectively remove greenhouse gases has emerged as a key global challenge. In particular, catalytic technology, which uses oxygen to decompose harmful gases, is an important element of environmentally friendly purification. Korean researchers have identified a principle that enables catalysts, which had previously been vaguely thought to simply make good use of oxygen, to selectively utilize different oxygen sources depending on the reaction environment, presenting a new standard for catalyst design.

On February 4, a joint research team consisting of Professor Lee Hyun-joo of KAIST’s Department of Chemical and Biomolecular Engineering, Professor Han Jeong-woo of Seoul National University, and Professor Park Jeong-young of KAIST announced that they were the first in the world to identify that ceria (CeO₂), which is widely used as an environmentally friendly catalyst, completely changes how oxygen is used depending on its size. *Ceria (CeO₂): A compound formed by combining metal cerium and oxygen.

Ceria is a metal oxide catalyst that provides high catalytic performance while reducing the need for expensive precious metal catalysts. In the field of catalysts, it is called an “oxygen tank” because it can store oxygen and release it when needed. However, until now it had not been clearly determined where the oxygen came from and under what conditions it was used in the reaction.

The research team focused on a new concept: a catalyst that “selects and uses oxygen depending on the situation,” rather than a catalyst that simply “uses oxygen well.” To this end, they fabricated catalysts with precisely controlled ceria sizes, from tiny nanosizes to relatively large sizes, and systematically analyzed the oxygen transfer and reaction processes.

As a result, it was confirmed that the small ceria catalyst plays an “agile” role, quickly capturing oxygen from the air and immediately using it for the reaction, while the large ceria catalyst plays a “sustainable” role, pulling the oxygen stored inside to the surface and continuing to supply it. In other words, for the first time, a design principle has been clarified that, by simply adjusting the size of the catalyst, it is possible to choose between using oxygen in the air or using oxygen stored inside depending on the reaction conditions. The research team simultaneously proved this mechanism through advanced experimental analysis and artificial intelligence-based simulations.

The research team applied this principle to methane removal. Methane is a greenhouse gas that has a global warming effect tens of times stronger than carbon dioxide, and is removed by a catalytic oxidation reaction that uses oxygen to convert it into carbon dioxide and water. As a result of experiments, it was found that the small ceria catalyst can demonstrate stable methane removal performance even in low temperature and high humidity environments by immediately utilizing oxygen in the air. This shows that it is possible to significantly reduce the use of expensive precious metals (platinum and palladium) while actually improving performance.

This result is expected to lead to the development of highly durable catalysts that maintain their performance even in realistic industrial environments such as rain and humidity, and to the reduction of manufacturing costs for environmental purification devices, accelerating the practical application of environmentally friendly energy and environmental technologies.

Application examples of ceria catalyst>

Professor Lee Hyun-joo said, “This research is the first to clearly distinguish between the two core mechanisms of how oxygen acts within a catalyst,” and “opens a new way to custom design high-efficiency catalysts needed to respond to the climate crisis according to reaction conditions.”

KAIST doctoral candidate Yunji Choi, Seoul National University’s Dr. Jung Seok-hyun, and KAIST doctoral candidate Jaebum Han served as co-lead authors of the study. This research result was co-authored by Hwang Je-eon, Hyun-jin, Kim Yoon-kyung, and Kim Jong-jin, and was published in the international academic journal “Nature Communications” on January 9th.

This research was supported by the National Research Foundation of Korea (Global Leaders Grant, Mid-Career Research Program) funded by the Ministry of Education, Science and Technology of the Republic of Korea.