INVESTIGATIONS INTO THE KINETICS OF SOFC CATHODES

摘要

Addition of zirconia to the porous perovskite structure of a SOFC cathode reduces the cathode polarization by 60%. A conventional cell membrane equipped with this kind of cathode was fed with a fuel mixture of 50% hydrogen and 50% water vapor. With air on the cathode side it could be loaded at 850℃ with 0.4 A/cm~2 at 0.7 V. The cell was characterized by taking current-voltage characteristics in the range of 750 to 950℃ and at oxygen partial pressures of 0.01 to 1.0 bar. To separate the contribution of the cathode, impedance spectra were taken at rest potential and under increasing load within the same range of ambient conditions. The field of current-voltage characteristics of the cathode was constructed. The porous electrode model fitted to the impedance data showed that the electrode thickness is well adapted to the structure. With an electrolyte material of higher ionic conductivity it should be possible to improve the cathode further.