Abstract
Solid Oxide Cells (SOCs) are devices that provide unique functionality and flexibility for a range of important energy conversion applications. They are most well known as Solid Oxide Fuel Cells (SOFCs) for clean efficient electrical generation, but can also be used as Solid Oxide Electrolysis Cells (SOECs) for production of renewable fuels (e.g., green hydrogen) with higher efficiency than other electrolysis technologies. Their flexibility also allows large-scale energy storage by switching between fuel cell and electrolysis modes (akin to discharge and charge modes in batteries), particularly for long-term grid “load shifting” – storing excess electricity for days and weeks. SOCs are now beginning to see large-scale commercialization, but improvements are needed to increase power densities and decrease degradation rates to allow long-term (>40,000 h) operation.
A number of the performance and stability issues are related to the Nickel-yttria stabilized zirconia (Ni-YSZ) fuel electrode widely used in SOCs. This talk will discuss a key current issue – Ni migration in Ni-YSZ fuel electrodes during electrolysis operation. Our recent results show that reducing the Ni-to-YSZ ratio mitigates Ni migration. Possible reasons for this difference are explored, including (1) that the lower Ni content electrode lowers the electrode polarization resistance, reducing the overpotential driving force for migration and (2) the low-Ni electrode possesses small isolated Ni-pore interfaces, limiting Ni surface diffusion.
Another approach is to switch out the Ni-YSZ with an electronically conducting oxide using a process called exsolution, where specific cations are reduced and nucleate metallic nanoparticles that enhance anode performance. Results on Sr(Ti,Fe,Ni)O3 electrodes, where Ni-Fe alloy nanoparticles form, are discussed. Recent in situ x-ray diffraction results are used to develop a thermodynamic model for predicting the Ni-Fe alloy composition.
Bio
Scott A. Barnett is a Professor in the Materials Science and Engineering department at Northwestern University in Evanston, Illinois, USA. After receiving his Ph.D. in Metallurgy from the University of Illinois at Urbana-Champaign in Metallurgy, he held postdoctoral appointments at the University of Illinois and Linkøping University. He took his present position at Northwestern University in 1986, and has also been Erasmus Mundus Guest Scholar at University Grenoble Alpes, Fulbright Guest Professor at Centro Atomico Bariloche, Otto Mønsted Guest Professor at the Danish Technical University, Cheng Tsang Man Endowed Professor at Nanyang Technological University, and a Visiting Scientist at Los Alamos National Laboratories. He served as the founder and Chief Technical Consultant of two companies: Functional Coating Technology LLC and Applied Thin Films Inc. He has authored or co-authored > 300 publications (h index of 90), has 15 patents, and has advised nearly 50 PhD students. Research topics have included semiconductor growth by molecular beam epitaxy, ion-assisted thin film deposition, nitride hard coatings and superlattices, solid oxide fuel cells and electrolyzers, Li-ion battery cathodes, and electrode materials characterization using three-dimensional tomography and impedance spectroscopy. He is an Electrochemical Society Fellow, AVS Fellow, American Ceramic Society Fellow, and was an Office of Naval Research Young Investigator. Current research interests include development and characterization of novel fuel-cell electrode materials, energy storage using solid oxide cells and Li-ion batteries, and accelerated testing to characterize cell degradation processes.
Zoom: https://msu.zoom.us/j/96582861807
Passcode: Seminar
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