Professor Lee Kwang-yeol’s group from the Department of Chemistry, College of Science at KU carried out a joint research project with Senior Researcher Yoo Sung-jong’s group from the Korea Institute of Science and Technology (KIST) and Professor Jung You-sung’s group from the Korea Advanced Institute of Science and Technology (KAIST) and together developed high-efficiency nanocatalysts that can significantly lower the price of producing environmentally friendly green hydrogen through water electrolysis. The nanoparticles they developed, ruthenium oxide particles with a slight amount of platinum, are anode catalysts for generating oxygen at an efficiency that is higher than the commercially available iridium and ruthenium oxide catalysts.
The results of this study were published in the online edition of Energy & Environmental Science (Impact Factor: 38.532), a globally acclaimed journal in the field of energy and environmental sciences, on November 12.
Water electrolysis is a technology for producing green hydrogen by degrading water through an electrochemical method. While the production of gray hydrogen from conventional fossil fuels emits 10 kg of carbon dioxide to produce 1 kg of hydrogen, water electrolysis, which is free of carbon dioxide emissions, is an environmentally friendly method for producing green hydrogen. To realize carbon neutrality, it is necessary to develop efficient water electrolysis technologies. This will require a high-efficiency catalyst for generating oxygen, for which iridium oxides have usually been employed. However, due to the high price of iridium (7 times as high as ruthenium and 4 times as high as platinum as of December 2021), the development of a material that can replace it is urgently needed. Ruthenium oxides are known to show high activity in the electrochemical reaction for generating oxygen when compared to iridium oxides. However, the electrochemical instability of ruthenium oxides prevents them from being applied to the actual operational environment of water electrolysis, as they are easily eluted into the electrolyte.
Professor Lee’s group introduced a small amount of platinum to the surface of ruthenium oxides and used the resulting materials as catalysts for the oxygen generation reaction of acidic electrolytes, showing that these novel catalysts have high energy efficiency and stable durability despite long-term operation.
The research team applied the newly developed ruthenium oxide-based nanocatalysts to a polymeric electrolyte-based water electrolysis system and showed that the water electrolysis performance was more than 2.5 times as high as that of commercial iridium oxide-based catalysts of the same weight at 2.0 V. The iridium used in commercial iridium oxide-based catalysts, which are most frequently applied to the anode of polymeric electrolyte-based water electrolysis systems, is more expensive than ruthenium, and the performance of iridium oxide-based catalysts is decreased when operated for a long time at a high voltage. The ruthenium-based nanocatalysts developed in this study have an economic feasibility that is 11 times as high as the commercial iridium oxide-based catalysts in terms of the amount of precious metals used, and they show stable catalytic activity despite long-term operation.
Professor Lee explained, “The core strategy of our technology was to introduce platinum to the surface of ruthenium oxides, which are highly unstable in an acidic electrolyte. The introduction of the relatively stable metal to the ruthenium oxides that are easily eluted into an electrolyte in the water electrolysis environment allowed us to develop the catalyst having both high performance and high durability.” Professor Lee added, “Our strategy may be employed to develop next-generation nanocatalysts that can replace conventional commercial catalysts.”
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