Evaluation of the thermal and structural stability of planar anode-supported solid oxide fuel cells using a 10 × 10 cm2 single-cell test

Abstract

The present work investigated the thermal and structural stability of planar anode-supported solid oxide fuel cells (SOFCs) using a 10 × 10 cm2 single-cell test. First, the gasket study was performed in which the sealing efficiency and hydrodynamics were examined to obtain the control parameters for sealing design. Two types of high-temperature gaskets were evaluated for application in the SOFC test, both with sealing efficiencies over 99.99%; both of them did not ensure the gas tightness perfectly, and we selected the fuel cell material gasket due to a lower leak factor than the Magnex gasket at whole inlet flow rates. After this gasket sealing test, the thermal and structural stability of a planar anode-supported SOFC was evaluated by changing temperature repeatedly between room temperature and 850 °C. For the first high flow test, the open circuit voltage (OCV) agreed with the theoretical value, and the voltage decreased linearly as the current density increased. In addition, the measured temperature distribution had a similar trend compared with the previous numerical analysis during the first reduction condition. However, after lowering the temperature and raising it again, the OCV during the second low flow test decreased and fuel crossover loss occurred; additionally, the voltage decreased irregularly as the current density increased. After completing the tests and dissembling the single cell specimen, the cracked mark was placed in the center of the cell like the calculated and measured results. From the dispersed oxygen contents in the anode using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy, we concluded that the crack was induced by the reduction and oxidation (RedOx) cycle instability from even a small leakage through the gasket. Finally, we found that the planar SOFC was vulnerable to the thermal RedOx cycle induced by non-perfect sealing, and it was confirmed that the requirement of the gas tightness should be fulfilled in order to obtain the longer life and the higher stability for the solid oxide fuel cell.