The stack sealing is one of the most important factors in planar solid oxide fuel cell (pSOFC) applications. In this study, the barium-silicate glass with addition of Al2O3 were analyzed by ICP, DSC, and SEM. Differential thermal analysis was utilized to design the heat-treatment of the glass to obtain a glass-ceramic for sealing. The glass material and sealing process were verified on the 114×114 mm SOFC stack. A tight stack was obtained with a leak rate much better than the desired 0.004 SCCM/cm, which is equivalent to 0.001 MPa/s. A good electric performance was also found for a 6-layer sealed stack. Post-characterization was conducted for the seal dismounted from the stack via the methods of leakage inspection, SEM-EDS, and XRD. A good interaction was found between the glass-ceramic seal and the steel interconnect, due to the diffusion of aluminum from the glass component.

Hydrogen of different concentrations humidified by the water vapour were used to reduce the NiO-8YSZ anodes of the solid oxide fuel cells (SOFCs) at 700℃ and 720℃. The experimental results suggested that four periods of the open circuit voltage, namely rapid increase period, temporary stasis period, slow increase period and final stable period exist successively during the reduction, the characteristics of which were closely related to the hydrogen concentration of the reduction. After the reduction, the polarization resistance on open circuit and on load showed different correlation with the hydrogen concentration of the reduction. The variation trend of the initial performances of the SOFCs corresponded highly to the polarization resistance on load. The shrinking core model of the reduction of the NiO suggested that the further reduction of the unreacted NiO core would most likely cause the activation of the SOFC.

The stack sealing is one of the most important factors in planar solid oxide fuel cell (pSOFC) applications. Two sealing approaches were used for the short stacks working under practical conditions, which are rigid bonded sealing with SiO2-BaO-based glass sealant and compressive sealing with ZrO2-based ceramic gasket. The prepared glass was characterized by inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and dilatometry to determine its component and structural and thermal properties. Once the stack system shut down, the bubble test was used to detect and locate the leak of the stack. Then post-test characterization was conducted to analyze the failure of the sealing. SEM-EDS and XRD were used to analyze the microstructure and the crystallization of the sealant inside and its interface with the interconnect. It was observed that the crystal was formed inside the glass sealant, which strengthened the material. Good adhesion and chromium diffusion were found between the glass sealant and the metal interconnect. Moreover, the lose the sealing glass under overheating was found close to the fuel inlet, which was suggested to lead to the failure of the stack. For the ZrO2-based ceramic sealing, the crack was observed inside the sealant and the airway was obstructed by the sealing material under the compressive force. In summary, the glass sealing was more controllable than the compressive ceramic gasket. However, the glass sealant should be protected from local overtemperature.