Electrochemical studies of Gd_0.5Pr_0.5BaCo₂O_{5 + δ} (GPBC) cathode for oxide ion and proton conducting solid oxide fuel cells

Recently, mixed ion and electron conducting layered perovskite-type LnBaCo₂O_{5 + δ} (Ln^{3 +} = rare earth) have been considered as cathodes for intermediate temperature (IT) solid oxide fuel cells (SOFCs). Here, we report the electrochemical performance of Gd_0.5Pr_0.5BaCo₂O_{5 + δ} (GPBC) for proton (H⁺) and oxide (O^{2 -}) conducting SOFCs. GPBC was prepared by conventional ceramic method in air at 900 °C. Symmetrical cell of proton conducting Ba_0.5Sr_0.5Ce_0.6Zr_0.2Gd_0.1Y_0.1O_{3 - δ} (BSCZGY) and GPBC showed an area-specific polarization resistance (ASR) of 2.4 Ω cm² and 1.9 Ω cm² at 700 °C for oxygen reduction reaction (ORR) in air and wet air, respectively, and exhibited an activation energy of 1.2 eV in both atmospheres. The observed low (∼ 10 times) ORR ASR performance of GPBC may be owing to thin and dense electrodes and low proton conducting BSCZGY electrolyte used in the present work. The ASR values can be improved by optimizing microstructure and thickness of electrodes. Symmetrical cell utilizing a commercial oxide ion conducting Y₂O₃-stabilized zirconia (8YSZ) (Tosoh) showed slightly higher ORR ASR and activation energy values (1.6 eV), which can be attributed to interfacial reaction with GPBC cathode during the cell fabrication at elevated temperature.