Durability test of SOFC cathodes

The durability of solid oxide fuel cell (SOFC) composite cathodes of lantha num strontium manganite and yttria stabilised zirconia was investigated. Th e cathodes were kept at constant, realistic operating conditions (-300 mA c m(-2) at 1000 degrees C in air) for up to 2000 h. After the 2000 h test the increase in electrode overvoltage exceeded 100% of the initial value. Nomi nally identical cathodes kept for 2000 h at 1000 degrees C in air without c urrent load for comparison showed little or no degradation. Thus, the curre nt load of -300 mA cm(-)2, rather than the operation temperature of 1000 de grees C, was responsible for the degradation. Structural analysis showed an increase in the porosity at the electrode interfaces, when the electrode h ad been polarised. No such structural changes were found for electrodes tes ted without current load. The degradation is primarily ascribed to pore for mation in the electrode material induced by an electric field.