Newswise – Dr. Hyung-Suk Oh and Dr. Woong-Hee Lee from the Clean Energy Research Center on Korea Institute of Science and Technology (KIST)in collaboration with POSTECH and Yonsei University, have developed a method to improve the reversibility and durability of electrodes using bifunctional platinum-nickel alloy catalysts with an octahedral structure that exhibit both oxygen reduction and oxygen generation reactions.
Bifunctional catalysts are a new generation of catalysts that simultaneously produce hydrogen and oxygen from water using a single catalyst. Currently, electrochemical systems such as water electrolysis technology and CCU (carbon dioxide capture and utilization) use separate catalysts for both electrodes, resulting in high unit costs of hydrogen production. On the other hand, bifunctional catalysts that can be synthesized in a single production process are attracting attention as a technology that can reduce production costs and increase the economics of electrochemical energy conversion technologies.
However, the problem with bifunctional catalysts is that after each electrochemical reaction that produces hydrogen and oxygen, the performance of other reactions decreases due to structural changes in the electrode material. Therefore, for the commercialization of bifunctional catalysts, it is important to ensure reversibility and durability so that the catalyst structure is maintained for a long period of time after the reaction.
To improve the reversibility and durability of the bifunctional catalyst, the team synthesized alloy catalysts with different structures by mixing platinum and nickel, which have high performance in oxygen reduction and generation reactions, respectively. The experimental results showed that the nickel-platinum interaction was most active in the octahedral structure and the alloy catalysts performed more than twice as well as the platinum and nickel monoliths in oxygen reduction and generation reactions.
The researchers identified platinum oxide formed during the repeated generation reaction of the alloy catalyst as the cause of the performance decline and developed a structural restoration method to reduce platinum oxide to platinum. The team confirmed through transmission electron microscopy that the method restored the shape of the catalyst, and in large-scale reactor experiments for commercialization, the team managed to restore the catalyst shape and more than double the run time.
The team’s bifunctional catalysts and structure recovery methodology are expected to accelerate the commercialization of unitized renewable fuel cells (URFC) technology by replacing the separate catalysts for oxygen evolution and reduction reactions with bifunctional catalysts. URFCs, capable of producing both hydrogen and electricity, can reduce production costs by reducing the use of expensive catalysts while maintaining performance.
“The technology to improve the reversibility and durability of catalysts has provided a new direction for the development of bifunctional catalysts, which are an important technology for electrochemical energy conversion systems,” said Hyung-suk Oh, senior researcher at KIST. “It will contribute to the commercialization and carbon neutrality of electrochemical systems such as URFCs in the future.”
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KIST was founded in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. Further information can be found on the KIST website at https://eng.kist.re.kr/
This research was supported by the Ministry of Science and ICT (Minister Lee Jong-ho) under the “KIST Institutional Program”, the “Carbon to X Project” (2020M3H7A109822921) and the “Creative Convergence Research Project” (CAP21013-100) National Research Council of Korea (Chairman Kim Bok-cheol). The results were published in the latest issue of the renowned international journal “Advanced Energy Materials” (IF: 27.8, top 2.5% in the JCR) and selected for the image on the back.