Effects of humidity on SrTi_(0.05)Co_(0.95)O_(3-δ) cathode properties and durability of solid oxide fuel cells

摘要

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 mecha- nism and related preventive methods. Here, effects of humidity on SrTi0.05Co0.95O3-delta (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 (R-p) increases with the increasing of the water vapor concentration in air. Compared with R-p measured in dry air, the enhanced R-p value is 0.0347 Omega cm(2) and 0.0493 Omega cm(2) in containing 3% and 5% H2O air after a continuous testing for 96 h at 800 degrees 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 degrees C, respecctively. Interestingly, the degradation coming from humidity can be recovered partially by switching the feedgas back to dry air again. The R-p of STC becomes -0.0402 c cm(2) again after switching the operating atmosphere from 5% H2O air to dry air for 5 h. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.