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 and gas environment, which significantly affect the performance and long-term stability. In general, SOECs exhibit inferior performance and stability compared to SOFCs, which limits the commercial development and deployment of this technology.In this research, degradation mechanisms of the air and steam electrodes were separately investigated through the electrochemical and microstructural investigations. The main cause of the degradation of the air electrode was found to be the cation migration occurring at the perovskite electrode due to oxygen evolution reaction, and high steam concentration at the steam electrode accelerated coarsening of nickel, leading to gradual increase of the polarization resistance. Degradation of the each electrode was suppressed by employing the novel electrode materials and optimizing the microstructure of the porous composite electrodes. Nano-scale catalysts were incorporated into the porous electrodes to further reduce the polarization resistance and enhance the efficiency. Electrode reaction kinetics and degradation mechanisms will be discussed in detail, and recent advances in SOEC research at Korea Insitutue of Science and Technology (KIST) will be presented.

Performance and stability of high-temperature solid oxide electrolysis cells (SOECs) for hydrogen production

246th National Meeting (2013)

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