Degradation Mechanism with Impurities and Life Time Estimation for SOFCs

The degradation of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode performance were investigated under relatively high pressures of impurities with Cr and S. AC impedance and DC currents were measured as a function of operation time. The cathode polarization rapidly increased when exposure to CrO3 and SO2 due to active sites vanishing with impurities. The distributions of Cr and S in the porous LSCF were different due to the chemical reactivity and electrochemical effects. A significant amount of SrCrO4 was deposited at the gas inlet of cathode surface region whereas small spots of SrSO4 were distributed inside the porous LSCF cathode. From the trends of polarization increase, the decrease trends and life time of cathodes were estimated for the availability of cathodes.