Suppression of Sr surface segregation in La0.8Sr0.2Co0.2Fe0.8O3-δ via Nb doping in B-site

Sr surface segregation has been one of the main reasons for the cathode performance degradation during the long-term operation of solid oxide fuel cells (SOFC). Investigation on Sr segregation mechanism and proposing strategies on suppressing the Sr surface segregation are significant for SOFC development. In this paper, La0.8Sr0.2Co0.2Fe0.8-xNbxO3-delta (LSCFNb, x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) are prepared via sol-gel method. The electrochemical performance and long-term stability are tested through electrochemical impedance spectroscopy (EIS) and constant current polarization. The results show that the long-term stability of LSCFNb cathodes are strongly affected by Nb content. Combining the results of ICP and XPS, it's revealed that the Sr surface segregation can be effectively suppressed with the increase of Nb content. The LSCFNb cathodes gain the optimal electrochemical performance when x = 0.04, with minimum polarization resistance of 0.27 Omega cm(2) at 750 degrees C and oxygen reduction reaction activation energy of 1.54 eV. After cathodic polarization for 144 h, the polarization resistance and activation energy of LSCFNb4 cathode increase slightly, revealing it a promising cathode material for SOFC research.

Automated summary

Sr surface segregation is a main issue affecting the cathode performance in solid oxide fuel cells (SOFC). This study investigates the Sr segregation mechanism and suggests strategies to suppress it by preparing a series of LSCFNb materials. Results show that increasing Nb content effectively suppresses Sr surface segregation and LSCFNb4 cathode exhibits promising performance for SOFC applications.