Solid oxide fuel cells (SOFCs) which can directly covert the chemical energy of fuel to electric energy have received as one of alternative energy sources because of their high energy conversion efficiency, fuel flexibility and low emission of pollutant to the environments. However, there are still several technical issues for making commercialization of SOFCs such as limited durability and long start-up time. Hence, recent studies of the SOFCs have focused on improving performance of SOFCs in the intermediate temperature (IT) to achieve technical goals such as high stability, low-cost component materials, easier sealing and quicker start-up time.

In particular, stable long-term performances of SOFCs are one of the essential factors for commercialization of fuel cell systems. However, the sudden unstable situations such as frequent electrical load on-off and high load can often occur during the SOFCs operations, and thus, these unexpected situations can affect the durability of SOFCs systems. Therefore, we need to investigate performance change of SOFCs under various electrical load conditions including the constant current, current on-off cycles and irregular current change. In addition, post-mortem analysis of SOFCs are necessary to find the main degradation mechanisms after various durability tests.

In this work, Ni-cermet anode supported cells are fabricated by the tape-casting method with neodymium doped ceria and double-perovskite structure based cathode materials (NdBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ). The performance of the cells are investigated by I-V measurement and the durability test also conducted by using load trip (0~200 mAcm^-2) and load cycle (120~200 mAcm^-2) techniques with controlled current condition at 650 ^oC.

For electrochemical analysis, electrochemical polarization and characterizations are conducted using an electrochemical impedance spectroscopy (EIS) with a Potentiostat/Galvanostat instrument using a frequency range from 1 MHz to 1Hz. The several physicochemical analyses are also investigated using field emission-scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD).

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Keywords : Solid oxide fuel cells; intermediate-temperature; durability; perovskite.