Modifying the cathodes of intermediate-temperature solid oxide fuel cells with a Ce 0.8Sm 0.2O 2 sol–gel coating

Abstract

To increase the performance of solid oxide fuel cells operated at intermediate temperatures (<700 °C), we used the electronic conductor La 0.8Sr 0.2MnO 3 (LSM) and the mixed conductor La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) to modify the cathode in the electrode microstructure. For both cathode materials, we employed a Sm 0.2Ce 0.8O 2 (SDC) buffer layer as a diffusion barrier on the yttria-stabilized zirconia (YSZ) electrolyte to prevent the interlayer formation of SrZrO 3 and La 2Zr 2O 7, 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 Ω cm 2 in air when measured at 700 °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.