Effects of humidity on SrTi0.05Co0.95O3-δ cathode properties and durability of solid oxide fuel cells

Abstract

Degradation suffering from ambient water vapor in air is harmful for cathodes of solid oxide fuel cells (SOFCs), it is necessary and important to research its attenuation mechanism and related preventive methods. Here, effects of humidity on SrTi0.05Co0.95O3-δ (STC) cathode have been discussed in detailed. X-ray diffraction analysis reveals that STC is relatively stable in wet air with a little crystal contraction, but without obvious impurities. Because active sites of STC for oxygen reduction reaction (ORR) are covered by water vapor, the electrical conductivity decreases while the polarization resistance (Rp) increases with the increasing of the water vapor concentration in air. Compared with Rp measured in dry air, the enhanced Rp value is 0.0347 Ω cm2 and 0.0493 Ω cm2 in containing 3% and 5% H2O air after a continuous testing for 96 h at 800 °C, respectively. Furthermore, a maxium power densities of 832 mW cm−2 and 814 mW cm−2 can be obtained for STC/LSGM/STC in dry air and containing 5% H2O air after 96 h operating at 800 °C, respecctively. Interestingly, the degradation coming from humidity can be recovered partially by switching the feedgas back to dry air again. The Rp of STC becomes ~0.0402 Ω cm2 again after switching the operating atmosphere from 5% H2O air to dry air for 5 h.