| 초록 |
Intermediate temperature solid oxide fuel cells (SOFCs) are well known as attractive energy conversion technologies for future electricity power generations. However, there are still drawbacks have to be solved, and one of the major problem in SOFCs is cathode poisoning by chromium from metallic interconnect. For this purpose, this study is concerned with Cr poisoning phenomena on (Ba,Sr)(Co,Fe)O3-δ (BSCF) cathodes. Fe-Cr alloy (RA446) was used as the interconnect materials. The alloys are machined into coupons with channels cut on one side of the coupon, and it is directly placed on the cathode for Cr poisoning test. In order to investigate the Cr poisoning on cathode material, impedance and polarization are taken under a constant current density of 200mAcm-2 in air at 900oC for 100h. The performance degradation of cathode is obviously found from the electrochemical analyses. In impedance results, both ohmic resistance and polarization resistance are increased and then saturated around 40-45h. Using the equivalent circuit, the measured impedances were fitted into high frequencies and low frequencies, and explained as a function of polarization time. These results can be summarized that the Cr poisoning directly affects the oxygen reduction reaction on cathode and electrochemical performance degradation. From SEM image analyses, it can be observed that the Cr deposits such as SrCrO4 and BaCrO4 are formed near the cathode particle and agglomerated each other. Microstructural changes at 0, 45 and 100 h poisoned samples are observed by SEM and the quantitative analyses of 45 and 100 h samples are conducted by SIMS analyses. From these results, the Cr deposition and poisoning mechanism can be suggested in detail. |
