Modifying the cathodes of intermediate-temperature solid oxide fuel cells with a Ce0.8Sm0.2O2 sol-gel coating

Abstract

To increase the performance of solid oxide fuel cells operated at intermediate temperatures (<700 degrees C), we used the electronic conductor La0.8Sr0.2MnO3 (LSM) and the mixed conductor La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) to modify the cathode in the electrode microstructure. For both cathode materials, we employed a Sm0.2Ce0.8O2 (SDC) buffer layer as a diffusion barrier on the yttria-stabilized zirconia (YSZ) electrolyte to prevent the inter-layer formation of SrZrO3 and La2Zr2O7, which have a poor ionic conductivity. These interfacial reaction products were formed only minimally at the electrolyte-cathode interlayer after sintering the SDC layer at high temperature; in addition, the degree of cathode polarization also decreased. Moreover to extend the triple phase boundary and improve cell performance at intermediate temperatures, we used sol-gel methods to coat an SDC layer on the cathode pore walls. The cathode resistance of the LSCF cathode cell featuring SDC modification reached as low as 0.11 Omega cm(2) in air when measured at 700 degrees C. The maximum power densities of the cells featuring the modified LSCF and LSM cathodes were 369 and 271 mW/cm(2), respectively, when using O-2 as the oxidant and H-2 as the fuel. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.