Electrochemical Impedance Spectroscopy of Core‐Shell Nanofiber Cathodes, with Ce$_{0.9}$Gd$_{0.1}$O$_{1.95}$ (Core) and Cu‐Doped La$_{0.6}$Sr$_{0.4}$MnO$_3$ (Shell), for Application in Solid Oxide Fuel Cells

Several core-shell nanofiber electrodes are prepared through electrospinning and tested for application as intermediate-temperature solid oxide fuel cell (IT-SOFC) cathodes. The materials investigated are La$_{0.6}$Sr$_{0.4}$MnO$_3$ (LSM), La$_{0.6}$Sr$_{0.4}$Cu$_{0.1}$Mn$_{0.9}$O$_{3-δ}$ (LSCuM_1), and La$_{0.6}$Sr$_{0.4}$Cu$_{0.2}$Mn$_{0.8}$O$_{3-δ}$ (LSCuM_2) perovskites, used at the shell side of the nanofibers. Ce$_{0.9}$Gd$_{0.1}$O$_{1.95}$ (GDC10) fluorite is used as the core material. The electrochemical characterization of the core-shell nanofiber electrodes is performed through electrochemical impedance spectroscopy (EIS). The EIS results are reported and discussed based on equivalent circuit modeling. The polarization resistance of the GDC10/LSM core-shell nanofibers electrodes is RP∼4.5 Ω cm$^2$ at 650 °C. Improvement is accomplished with GDC10/LSCuM_1 and GDC10/LSCuM_2 core-shell nanofibers, with R$_P$∼1.8 Ω cm$^2$ and 1.7 Ω cm$^2$ respectively at 650 °C. Post-test SEM characterization is carried out, to ascertain possible degradation and identify the most promising shell perovskite.