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Detailed Program
Paper Number : FU-I02
Time Frame : 13:55~14:20
Presentation Date : Thurse day, 27, November
Session Name : Fuel cells and batteries
Session Chair 1# : Hyung-Tae Lim
Session Chair 2# : Naoaki Yabuuchi
Solid Oxide Electrolysis Cell (SOEC) Technology for Hydrogen Production
Kyung Joong Yoon
Korea Institute of Science and Technology
Solid oxide electrolysis cells (SOECs) represent one of the most efficient and environmentally clean technologies for conversion of steam into hydrogen, especially when utilizing excess electricity and heat supplied from renewable energy sources, nuclear power plants or high-temperature industrial processes. The overall reaction of SOEC for steam electrolysis is the reverse of solid oxide fuel cell (SOFC) reaction, and, in principle, the identical cell can operate as both SOFC and SOEC. However, two operating modes differ in the electric potential gradient, gas environment and heat requirement, which significantly affect the performance and long-term stability. In general, dedicated SOFCs exhibit inferior performance and stability in electrolysis mode, which emphasizes the importance of material development and microstructural optimization for SOEC operation.
In this research, degradation mechanism of the air electrode was investigated through the electrochemical and microstructural investigations. The main cause of degradation and failure was found to be the cation migration occurring in the perovskite electrode due to oxygen partial pressure change and externally applied electric field. Cation migration was suppressed by employing mixed ionic- and electronic- conducting electrode materials which has no oxygen excess nonstoichiometry in the SOEC operating conditions. The rate limiting process for oxygen evolution reaction was identified to be the chemical surface exchange, and the electrochemical performance of the air electrode was significantly improved by incorporation of nano-catalysts into the porous scaffold. In addition, the performance of an SOEC was strongly influenced by the gas diffusion limitation at the fuel electrode. Transport model was developed to understand the transport phenomena of SOECs, and the hydrogen production rate was improved by a factor of greater than two by increasing the porosity and optimization of the pore distribution. The 200 W-class stack was successfully configured, and stable operation was confirmed at a thermal neutral voltage for over 1000 hours.
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