A novel symmetrical bi-electrode supported ceramic oxygen pump for efficient oxygen production

Abstract

Based upon the solid oxide electrolysis cell (SOEC) technology, ceramic oxygen pumps (COPs) show great promise owing to their distinctive advantage of continuous and in situ production of high-purity oxygen with control easiness. Here we report on the fabrication of novel ceramic oxygen pumps by the phase-inversion tape casting, lamination and co-firing methods, featuring thin yttria-stabilized zirconia (YSZ) electrolytes supported on symmetrical La0.8Sr0.2 MnO3-δ (LSM)-YSZ electrodes with straight open pores. A current density of 0.33 A•cm−2 is obtained at 750°C and 0.6 V for the ceramic pumps to separate oxygen out of air. Impregnating nano-scale La0.6Sr0.4CoO3-δ (LSC) catalysts into both LSM-YSZ electrodes yields a sharp increase in the performance. For example, the pumping current density at 750°C and 0.6 V increases by a factor of 8 to 2.56 A•cm−2. The total interfacial polarization resistance decreases from 1.17 Ω•cm2 by a factor of 20 to 0.06 Ω•cm2. Analysis of impedance data in the homogeneous environments of air and oxygen indicates that the oxygen separation capability is predominantly limited by the surface oxygen exchange kinetics, which is substantially promoted by the added LSC catalysts. Preliminary short-term measurements show good stability in oxygen separation, indicating excellent resistance of the nano-scale LSC catalysts against coarsening at elevated temperatures. Furthermore, the present symmetrical ceramic oxygen pumps also demonstrate excellent thermal cycling durability.