The effect of gadolinium-doped ceria interlayer on the oxygen reduction reaction in a LSCF cathode-ScSZ electrolyte supported IT-SOFCs

Solid oxide fuel cells (SOFCs) are rapidly emerging as a technology, offering the potential for carbon neutral or carbon negative generation of electricity and heat (combined heat and power) using synthetic carbohydrate fuels and hydrogen. A significant challenge associated with SOFCs is the high polarization resistance experienced at the cathode during the oxygen reduction reaction (ORR), which diminishes the cell efficiency. The kinetics of the ORR are influenced by factors such as the cathode material type, its microstructure, and the quality of the interface between the cathode and electrolyte. In our research, we have addressed this issue by modifying the interface between the state-of-the-art cathode material, Lanthanum Strontium Cobalt Ferrite—La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), and the Scandia stabilized Zirconia (ScSZ) electrolyte. This modification involved the deposition of a micron-sized film of ion-conducting gadolinium-doped ceria (Gd0.1Ce0.9O2-δ) – (GDC) as an interface layer. Our analysis involved systematic studies, including variations in cell operating temperatures and applied potentials, as well as measurements of cell performance over an extended period. We observed a significant enhancement in cell performance with the introduction of the GDC interfacial layer between the LSCF cathode and ScSZ electrolyte. Specifically, we recorded a cathode polarization resistance as low as 0.40 Ωcm2 for the modified interface, which is substantially lower compared to bare LSCF cathodes (3.04 Ωcm2) at 600 °C. This reduction in cathode resistance can primarily be attributed to the improved conditions for the oxygen reduction reaction (ORR), resulting from enhanced interfacial contact between the electrode and the electrolyte and mitigation of any zirconium interdiffusion as seen from detailed scanning electron microscopic studies.