Solid oxide electrolysis cell (SOEC) technology is one of the most efficient methods for producing clean hydrogen. However, electrode delamination remains a significant issue. To identify the causes of electrode delamination, recent studies have employed advanced transmission electron microscopy (TEM) and density functional theory (DFT) to discover nanoscale interface degradation.
Oxygen ions, which migrate through the electrolyte, participate in chemical reactions at the three-phase interface where they meet the air electrode, producing oxygen gas. Electrons are transferred via the air electrode. However, some oxygen ions that do not engage in the chemical reactions accumulate within the electrolyte. These accumulated oxygen ions deform the atomic structure of the electrolyte, leading to the formation of nano defects and subgrains, which eventually cause cracks in the solid oxide electrolysis cell.
Using electron beam diffraction analysis with advanced TEM, the research visually confirmed the stress formed at the electrolyte interface. Additionally, density functional theory (DFT) was used to reveal the phenomenon of reduced atomic distances resulting from the accumulation of oxygen ions.
Dr. Hye Jung Chang and Dr. Kyung Joong Yoon (Director) of the Hydrogen Energy Materials Research Center at the Korea Institute of Science and Technology (KIST, President Sangrok Oh) have announced that they have elucidated the mechanism of the initial degradation phenomenon that triggers the performance drop of high-temperature solid oxide electrolysis cell systems, using advanced transmission electron microscopy. Unlike previous studies, which analyzed the final stages of degradation at the micrometer scale (1 µm, one-millionth of a meter), this study successfully verified the initial changes in electrolysis cell materials at the nanometer scale (1 nm, one-billionth of a meter).
The research team identified the degradation mechanism occurring between the air electrode and electrolyte of the electrolysis cell through TEM diffraction analysis and theoretical calculations. The observations revealed that oxygen ions accumulated at the interface of the electrolyte, known as Yttria Stabilized Zirconia (YSZ), during the oxygen injection process that that drives the electrolysis reaction.
Consequently, the atomic structure of the interfacial YSZ is compressed, leading to the formation of nanoscale defects and, eventually, cracks between the air electrode and the electrolyte, which in turn caused the deterioration of the cell's performance. Furthermore, by visually verifying the stress and defects formed at the interface, the team succeeded in elucidating the correlation between ions, atoms, nanoscale defects, pores, and cracks occurring in the early stages of degradation.
This research achievement marks the first study to elucidate the degradation mechanism at the nanoscale, providing guidelines to address the performance decline of high-temperature electrolysis cells during long-term operation. Specifically, it could enable the development of materials that can operate stably above 600°C for extended periods, significantly enhancing the durability of commercial electrolysis cells. The nanoscale analytical technology using advanced TEM in this study can be applied to solve degradation issues in various energy devices.
The research team plans to accelerate the commercialization of high-temperature electrolysis cells by collaborating with manufacturers to establish automated production processes for mass production. Additionally, they are conducting research to develop new materials that can suppress the accumulation of oxygen ions in specific areas of the electrolysis cell, aiming to increase production efficiency and reduce production costs, ultimately lowering the cost of clean hydrogen production.
Dr. Chang from KIST stated, "Using advanced transmission electron microscopy, we were able to identify the causes of previously unknown degradation phenomena at the early stages. Based on this, we aim to present strategies to improve the durability and production efficiency of high-temperature electrolysis cells, contributing to the economic viability of clean hydrogen production."
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KIST was established 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. For more information, please visit KIST’s website at https://eng.kist.re.kr/
This research was supported by the Ministry of Science and ICT (Minister Sang Im Yoo) through KIST's major project and the Ministry of Trade, Industry, and Energy (MOTIE) of Korea (Minister Deokgeun Ahn) (P0022331) supervised by the Korea Institute for Advancement of Technology (KIAT), along with National Research Council of Science and Technology (CAP22072-000), The findings have been published in the latest issue of the international journal Energy & Environmental Science (IF 32.4, JCR field 0.9%).
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Credit: Korea Institute of Science and Technology
Caption: Solid oxide electrolysis cell (SOEC) technology is one of the most efficient methods for producing clean hydrogen. However, electrode delamination remains a significant issue. To identify the causes of electrode delamination, recent studies have employed advanced transmission electron microscopy (TEM) and density functional theory (DFT) to discover nanoscale interface degradation.
Credit: Korea Institute of Science and Technology
Caption: Oxygen ions, which migrate through the electrolyte, participate in chemical reactions at the three-phase interface where they meet the air electrode, producing oxygen gas. Electrons are transferred via the air electrode. However, some oxygen ions that do not engage in the chemical reactions accumulate within the electrolyte. These accumulated oxygen ions deform the atomic structure of the electrolyte, leading to the formation of nano defects and subgrains, which eventually cause cracks in the solid oxide electrolysis cell.
Credit: Korea Institute of Science and Technology
Caption: Using electron beam diffraction analysis with advanced TEM, the research visually confirmed the stress formed at the electrolyte interface. Additionally, density functional theory (DFT) was used to reveal the phenomenon of reduced atomic distances resulting from the accumulation of oxygen ions.
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