"Unfazed Even at Minus 20 Degrees" National Research Foundation of Korea Solves Hydrogen Fuel Cell Freeze Cracking

Core technology that can maintain the performance and durability of hydrogen fuel cells during winter has been developed domestically. Until now, there have been issues with decreased performance and durability of hydrogen fuel cells in winter due to 'electrode freeze cracking.' Electrode freeze cracking occurs when residual water inside the hydrogen fuel cell electrode freezes, causing cracks, and is a major factor in shortening the lifespan of fuel cells during severe cold.

The National Research Foundation of Korea announced on November 6 that a research team led by Professor Jaebum Pyo from Kongju National University, Professor Taeksu Kim from KAIST, and Dr. Jihoon Kim from the Agency for Defense Development has identified that freezing inside the 'ionomer binder' is the cause of electrode freeze cracking, and has solved the problem by applying a heat treatment process at 190 degrees Celsius for 10 minutes.

(From left) Professor Jaebum Pyo, Professor Taeksu Kim from KAIST, Dr. Jihoon Kim from the Agency for Defense Development. Provided by the National Research Foundation of Korea

An ionomer is a polymer that absorbs water to transfer charges such as hydrogen ions, while also serving to bond and support particles. The heat treatment process refers to a method that improves performance by altering the physical and chemical structure of the material. The joint research team succeeded in densifying the nanostructure of the ionomer through this process, effectively blocking spaces where water could remain.

Hydrogen fuel cells and water electrolysis devices are considered core technologies for future clean energy. However, during harsh winter conditions, water remaining inside the electrodes can freeze, leading to cracks and resulting in decreased device performance and shortened lifespan.

Previous studies generally attributed such damage to pressure caused by water trapped in the nanopores inside the electrodes freezing, and up to now, solutions have relied on raising the temperature using heaters or external auxiliary devices.

In contrast, the joint research team discovered that electrodes with a high ionomer content have fewer nanopores and better initial mechanical performance, but are actually more susceptible to freeze cracking. This indicates that the main culprit of freeze cracking is not the nanopores, but rather the 'ionomer binder,' which absorbs water like a sponge.

Having identified the cause of freeze cracking, the joint research team applied a heat treatment process at 190 degrees Celsius for 10 minutes to solve the problem. During this process, the nanostructure of the ionomer was densely modified, controlling the very space where water could remain. As a result, they achieved durability that maintained over 90% of the initial mechanical performance even in extreme cold at minus 20 degrees Celsius.

Professor Pyo stated, "This study is significant in that it overturns the conventional wisdom about the cause of electrode freeze cracking, identifies the true cause, and presents a new solution."

However, Professor Pyo added, "To apply these research results in industrial settings, long-term repeated freeze-thaw tests and verification in actual power generation system environments are necessary. The joint research team will further develop this research into technology applicable to large-scale systems, contributing to the development of next-generation hydrogen energy systems that can operate stably even in extreme environments."

This research was supported by the Mid-career Researcher Program and Basic Research Program funded by the Ministry of Science and ICT and the National Research Foundation of Korea. The research results (paper) were recently published in the international journal 'Carbon Energy,' which specializes in energy and materials science.