Long-Term Stability of Perovskite-Based Fuel Electrode Material Sr2Fe2-XMoxO6-δ – GDC for Enhanced High-Temperature Steam and CO2 Electrolysis

Abstract

Solid oxide electrolysis cells (SOECs) have proven to be a highly efficient key technology to produce valuable gases (H2, CO). SOECs utilize renewably generated electricity at temperatures between 600 - 900 °C, thereby providing a carbon-neutral method for energy storage. However, the successful industrial implementation of this technology requires long-term stability of all system components and is mainly delayed by the degradation of the electrodes over time. The state-of-the-art Ni-YSZ fuel electrode has been extensively studied and exhibits severe performance loss due to Ni particle agglomeration and Ni migration away from the active sites at the electrolyte/electrode interface under real operating conditions [1]. To mitigate this issue, we have investigated the Ni-free perovskite Sr2Fe2-xMoxO6-δ + 30% GDC as fuel electrode material. As mixed ionic and electronic (MIEC) perovskite structured oxides, these materials have shown excellent short-term redox stability in oxidizing and reducing atmospheres in addition to high conductivity and outstanding coking resistance [2]. These characteristics meet exactly the targeted requirements for new solid oxide electrolyzer materials. We have compared the long-term degradation of an SFM fuel electrode to an electrode made of SFM-GDC (Figure 1). The degradation was less severe for the mixed electrode of SFM-GDC. Impedance and post-test SEM-EDX analysis clarified the main degradation mechanisms of SFM as well as SFM-GDC in steam and CO2 electrolysis. The tested button cells showed demixing of the SFM phase and particle aggomeration in the fuel electrode.[1] S. E. Wolf, V. Vibhu, E. Tröster, I. C. Vinke, R.-A. Eichel and L. G. J. de Haart, Energies, 15(15), 5449 (2022).[2] L. Bernadet, C. Moncasi, M. Torrell and A. Tarancón, Int. J. Hydrog. Energy, 45(28), 14208–14217 (2020). Figure 1