Insight into the oxygen reduction reaction on the LSM|GDC interface of solid oxide fuel cells through impedance spectroscopy analysis
Doped ceria is commonly used to promote the performance of solid oxide fuel cells (SOFCs) with a lanthanum strontium manganite (LSM) cathode, but the oxygen reduction reaction (ORR) activity on the interface between LSM and doped ceria is not conclusive due to the complexity of the cathode and problematic analysis of the impedance spectra. Here, to elucidate the role of the LSM|GDC interface in the ORR, we constructed a simple LSM|GDC interface and analyzed the impedance data using a method based on the calculation of the distribution function of relaxation times (DRT). DRT analysis demonstrates that the ORR on the LSM|GDC interface possesses similar activation energies for oxygen dissociation and the subsequent oxygen atom reduction but involves an easier oxygen incorporation process in comparison with the LSM|YSZ interface. Addition of the GDC interlayer causes a decrease in cell performance because poor LSM|GDC interfaces lead to depressed dominant electrode processes of oxygen dissociation and the subsequent oxygen atom reduction. These results provide useful insight into the ORR on the LSM|GDC interface, favoring the design of a high-performance doped ceria-enhanced LSM cathode.