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| Book/Dissertation / PhD Thesis | FZJ-2026-02713 |
2026
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-937-4
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-02713
Abstract: Recently, a novel solid oxide cell was developed for the production of green hydrogen via water electrolysis and electricity from hydrogen respectively. The cell is fuel electrode supported and utilizes a Ni-CGO composite as fuel electrode instead of Ni-YSZ as used in state-of-the-art cells. Additionally a three-layer electrolyte composed of a thick CGO layer and two barrier layers, YSZ acting as electronic blocking layer and CGO as diffusion barrier to suppresses the reaction of YSZ with the air electrode. In initial studies the cell showed excellent performance in fuel cell mode, yielding a cell voltage of 1.1V at 800 °C and a current density of 1.94A cm−2. During electrolysis operation, however, failure occurred. At temperatures below 750 °C, a reduced open circuit voltage, an increase in cell voltage at high current densities and crack formation in the three-layer electrolyte were observed. The barrier layers are typically deposited via physical vapor deposition. However, they can also be manufactured using screen printing and co-sintering with the thick electrolyte layer and fuel electrode. It was shown that the manufacturing of the barrier layers strongly influences the electrolyte’s microstructure. Beside changes in layer thickness, interdiffusion and interface porosity might be enhanced. These effects most likely will influence the cell performance and mechanical stability during operation. Cell failure in the form of crack formation, that was observed at 700 °C and high current densities, most likely originate from defects in the electrolyte, such as pores and leaking barrier layers. Mechanical properties are strongly influenced by defects. Especially the fracture toughness of CGO decreases rapidly with increasing porosity at operation temperature under reducing atmospheres. Due to the different expansion of the layers caused by thermal and, in the case of CGO, chemical expansion, large mechanical stresses are existent within the cell. Additionally, a gradient in these stresses occurs across the cell’s thickness. Both promote crack formation in the multi-layer system and cell failure.
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