Operando Environmental TEM Analysis of Interface Degradation in Perovskite Electrodes for Solid Oxide Cells

Solid oxide electrolyzers and fuel cells (SOEC/SOFC) hold significant potential for reducing global carbon emissions. However, achieving greater durability and cost-effectiveness requires a deeper understanding of their degradation mechanisms during operation. Traditional post-test analyses offer limited insights into the dynamic degradation processes occurring in real-time. To address this challenge, we have developed an innovative method that integrates TEM characterization with simultaneous electrochemical testing, allowing a direct correlation between structural and compositional changes and electrochemical performance. This methodology employs a specialized TEM holder equipped with a heating-biasing MEMS chip and an environmental TEM capable of introducing reactive gases such as O 2 , H 2 , and H 2 O, effectively mimicking real-world SOEC/SOFC operating conditions. A dedicated sample preparation technique enables the simultaneous application of heat, reactive gases, and electrical bias [1-4]. In this study, perovskite-based electrodes, including lanthanum-strontium-cobalt oxide (LSC) and lanthanum-strontium-ferrite (LSF), paired with yttrium-stabilized zirconia (YSZ) electrolytes and gadolinium-doped ceria (CGO) buffer layer, were investigated. To study degradation phenomena, the cells were polarized under 2.7 mbar O 2 at 750 °C. (S)TEM imaging revealed phase transformations in negatively polarized perovskite electrodes and crack formation at the LSC/YSZ interface in positively polarized regions. Combined STEM-EELS and STEM-EDS analyses tracked valence state changes and the migration of iron, cobalt and strontium, while EIS measurements captured variations in surface reaction resistance simultaneously. These findings demonstrate a method for real-time observation of dynamic structural evolution, directly correlated with electrochemical performance testing. Acknowledgements This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 850850)” Reference [1] Ma, Zhongtao, et al. “Experimental Requirements for High‐Temperature Solid‐State Electrochemical TEM Experiments.” Small Methods (2024): 2301356. [2] Ma, Zhongtao, et al. “Electrochemical impedance spectroscopy integrated with environmental transmission electron microscopy. ” Small Methods (2023): 2201713. [3] Ma, Zhongtao, et al. “Operando Electron Microscopy and Impedance Analysis of Solid Oxide Electrolysis and Fuel Cells” ACS Energy Letters (2024): 9, 2007 [4] Ma, Zhongtao, et al. “Visualizing interface degradation of solid oxide cell”, in submission.