Abstract
The electrochemical performance of solid oxide fuel cell (SOFC) depends on functional properties of the anode, the cathode and the electrolyte that are being employed. There is a need for better cathode catalyst to decrease operating temperature of SOFCs. Here, we report a layered perovskite-type Ruddlesden-Popper structure La0.6Sr1.4Co0.2Fe0.8O4+δ (RP-LSCF) as cathode for SOFCs. The structural stability, thermal expansion, electrical, and fundamental electrochemical properties of RP-LSCF were investigated. The O2 reduction reaction (ORR) and O2surface exchange properties of RP-LSCF and Gd-doped CeO2 (GDC)-RP-LSCF composite were studied using symmetrical cells. Area normalized resistances for charge transfer (Ri) and surface exchange processes (Rs), and total polarization are found to be 0.14, 0.28 and 0.42 Ω cm2 at 800 °C, respectively. The exchange current density and oxygen surface exchange co-efficient for RP-LSCF are 54.53 mA cm−2 and 1.15 × 10−6 cm s−1 at 800 °C, respectively. Addition of nano-GDC with RP-LSCF leads to increase of polarization resistances, while the activation energies for charge transfer and surface exchange processes are reduced significantly. For the first time, we report a dielectric loss tangent analysis corresponding to the electrode phenomena in RP-LSCF and GDC-RP-LSCF to understand the electrical losses associated with SOFC cathode (ORR) processes.