As the climate crisis becomes a part of daily life with unprecedented heatwaves and cold snaps, technology to effectively remove greenhouse gases is emerging as a critical global challenge. In particular, catalytic technology that decomposes harmful gases using oxygen is a key element of eco-friendly purification. South Korean researchers have identified the principle that catalysts—which were previously vaguely thought to simply ‘use oxygen well’—can selectively utilize different oxygen sources depending on the reaction environment, presenting a new standard for catalyst design.
A joint research team consisting of Professor Hyunjoo Lee from KAIST Department of Chemical and Biomolecular Engineering, Professor Jeong Woo Han from Seoul National University, and Professor Jeong Young Park from KAIST announced on February 4th that they have identified for the first time in the world that ceria (CeO₂), widely used as an eco-friendly catalyst, completely changes its method of using oxygen depending on its size. *Ceria (CeO₂): A compound formed by the combination of the metal cerium and oxygen.
Ceria is a metal oxide catalyst enables high catalytic performance while reducing the need for expensive precious metal catalysts. It is called an ‘oxygen tank’ in the field of catalysis because it can store oxygen and release it when needed. However, until now, it had not been clearly identified where the oxygen came from and under what conditions it was used in the reaction.
The research team focused on a new concept of a catalyst that ‘chooses and uses oxygen according to the situation,’ rather than just a catalyst that ‘uses oxygen well.’ To this end, they fabricated catalysts with precisely controlled ceria sizes, ranging from ultra-small nano-sizes to relatively large sizes, and systematically analyzed the oxygen movement and reaction processes.
As a result, it was confirmed that small ceria catalysts operate as an ‘agility type’ that quickly takes in oxygen from the air and uses it immediately for reactions, while large ceria catalysts play an ‘endurance type’ role that pulls oxygen stored inside to the surface and supplies it continuously. In other words, the design principle was revealed for the first time that by simply adjusting the size of the catalyst, one can choose whether to use oxygen from the air or oxygen stored internally depending on the reaction conditions. The research team proved this mechanism simultaneously through advanced experimental analysis and artificial intelligence-based simulations.
The research team applied this principle to methane removal. Methane is a greenhouse gas with a global warming effect dozens of times stronger than carbon dioxide, and it is removed through a catalytic oxidation reaction that converts it into carbon dioxide and water using oxygen. The experimental results showed that the small ceria catalyst, by immediately utilizing oxygen from the air, demonstrated stable performance in removing methane even in low-temperature and high-humidity environments. This shows that it is possible to significantly reduce the use of expensive precious metals (platinum and palladium) while actually improving performance.
This achievement is expected to lead to the development of highly durable catalysts that maintain performance even in realistic industrial environments such as rain and moisture, as well as reducing the manufacturing cost of environmental purification equipment, thereby accelerating the commercialization of eco-friendly energy and environmental technologies.
Professor Hyunjoo Lee stated, “This research is an achievement that clearly distinguishes the two core mechanisms of how oxygen operates in catalysts for the first time,” and added, “It has opened a new path to custom-design high-efficiency catalysts required for responding to the climate crisis according to reaction conditions.”
Ph. D candidate Yunji Choi from KAIST, Dr. Seokhyun Choung from Seoul National University, and Ph. D candidate Jaebeom Han from KAIST participated as joint first authors of this study. The research results, also co-authored by Jae-eon Hwang, Hyeon Jin, Yunkyung Kim, and Jeongjin Kim, were published in the international academic journal 'Nature Communications' on January 9th.
This research was supported by the National Research Foundation of Korea (Global Leader Grant, Mid-Career Research Program) funded by the Ministry of Education, Science and Technology, Republic of Korea.