This study focuses on the preparation and characterization of composite gaskets designed for the sealing of the solid oxide cell stacks operating below 700 °C. The seals were fabricated with the addition of various amounts (10–90 wt.%) of 3 mol.% yttria partially stabilized zirconia to a BaO-Al₂O₃-CaO-SiO₂ glass matrix. The sample gaskets in the form of thin frames were shaped by tape casting. The quality of the junctions between the composites and Crofer 22APU steel commonly used as an SOC interconnect was evaluated after thermal treatment of heating to 710 °C, then cooling to the working temperature of around 620 °C and then leaving them for 10h in an air atmosphere, before cooling to room temperature. The samples were also studied after 3, 5, and 10 thermal cycles to determine the changes in microstructure and to evaluate the porosity and possible crystallization of the glass phase. The compression of the seals was calculated on the basis of differences in thickness before and after thermal treatment. The influence of zirconia additions on the mechanical properties of the seals was studied. The experimental results confirmed that glass–ceramic composites are promising materials for gaskets in SOC stacks. The most beneficial properties were obtained for a composite containing 40 wt.% of YSZ.

The primary limitation of Solid Oxide Cell (SOC) technology lies in the rapid degradation of cells during electrolysis mode. To address these issues while maintaining the core design of the cells, incorporation of the a composite electrode with fine-tuned microstructure proposed to reduce the risk of air electrode delamination. This composite consists of a buffer layer material (Gd0.1Ce0.9O2, GDC) and a state-of-the-art electrode (La0.6Sr0.4CoO3-δ, LSC), which minimizes the thermal expansion mismatch between the electrode, buffer layer, and electrolyte. Additionally, altering the electrode microstructure, for instance by adding a pore-forming agent, can improve the collection of oxygen during operation in SOE mode, thus preventing the development of potential differences and stress at the electrode-electrolyte interface. This study evaluated the electrochemical performance of solid oxide cells (SOCs) featuring a modified composite LSC-GDC air electrode with a gradual composition gradient. Batch of four different types of air electrode configurations were proposed and tested at the single-cell level (50 mm x 50 mm), and the most promising designs were implemented in SOC stacks (3–5 cells of 110 mm x 110 mm). Electrochemical analysis included j-V curve measurements and EIS spectra under SOE mode, including lon-term testing. Microstructural, morphological, and compositional analyses of the fabricated and tested cells were conducted using SEM, and SEM-EDS. The results demonstrated that a gradual reduction in GDC content across the electrode layers effectively produced a stable air electrode (tests > 300 h) with high catalytic activity, minimizing the risk of delamination. Acknowledgments The presented research was financially supported by: the National Centre for Research and Development, Poland, within project no. LIDER/1/0003/L-12/20/NCBR/2021. Anna Niemczyk acknowledges support from the Foundation for Polish Science through a scholarship from the START program.

The paper presents the experimental results of applying a novel protective coating made from Mn_1.7Cu_1.3-xFe_xO₄, compared to commercial spinels Mn_1.5Co_1.5O₄ and MnCo₂O₄, as a key component responsible for preventing chromium diffusion and slowing the increase in area-specific resistance (ASR) in solid oxide fuel cells (SOFCs). The layers of selected materials were deposited on Crofer 22APU steel by electrophoretic deposition (EPD) on small samples and by roll painting on full-scale interconnects. The coatings were evaluated by measuring the ASR of small samples for short and long runs (1000 h), as well as real-scale interconnects assembled in a SOFC stack composed of three cells, measuring 11 × 11 cm², which operated for 1000 h at 670 °C. The collected data on the electrochemical performance of the stack allowed for estimation of the degradation rates of all the repeating units, revealing benefits from using (Mn,Cu,Fe)₃O₄ as a coating. The results are compared to the literature reports. Post-mortem analysis by the SEM-EDS technique allowed for investigation of Cr diffusion levels.

Commercialization of solid oxide cell-based devices requires the introduction of low-cost and abundant materials to decrease production expenses. One of the bottlenecks in state-of-the-art SOFC and SOE stacks design is an interconnect steel. While Crofer 22APU from VDM Metals, Acerinox is the dedicated and proven solution, it is expensive and not readily available in large amounts. The known alternative includes less specific ferritic steels, namely AISI 441 and AISI 444, and widespread AISI 430. Substitution of the Crofer 22APU with alternative steels requires a thorough investigation of the novel protective layers on the air side and the stability of the interconnect exposed to the DC under high drops of oxygen and hydrogen chemical potentials. The dedicated test rig was developed and built in the Institute of Power Engineering – National Research Institute (IEN-PIB) for the dual-atmosphere studies of the ASR on stacked steel samples. In this rig the investigated samples can be assembled in the pseudo-stack with up to 14 steel-to-steel interfaces and a visible contact surface of 3x3 cm ² (direct contact area ~2.4 cm ² ). Half of the samples are corrugated in a manner that should represent the shape of the real interconnects. Pseudo-stack is sealed with mica-glass composite and operated being fed with air and with the 50 vol.% H ₂ O-50 vol.% H ₂ mixture. Usage of the LSCF as a contact helper allows trap the volatile Cr compound in case of the misfunction of the protective layer for the further analysis. The test rig supports the application of the current up to 30 A and continuous long-term operation (+ 1000 h). Preliminary tests demonstrated that at reference samples ASRs stay on the air side of the level of 10-15 mΩ*cm ² and for the fuel side observed values are below 0.5 mΩ*cm ² with minor degradation after 200 h of measurements at 700 °C. Work was supported by the National Science Centre NCN, Poland, grant UMO-2023/49/B/ST8/03265.