Synthesis of Graded in Composition and Microstructure Cathode Films for IT-SOFCs by Electrostatic Spray Deposition(ESD)

Abstract

Graded and controlled porosity of cathodes for solid oxide fuel cells have been studied. The cathodes are composed of strontium-doped samarium cobaltite (Sm0.5Sr0.5CoO3, SSC) and samarium-doped ceria (Sm0.2Ce0.8O1.9, SDC). The nanostructured composite cathodes graded in both composition and microstructure have been successfully fabricated on a SDC electrolyte by electrostatic spray deposition (ESD) method. The SSC has good electrochemical properties for intermediate-temperature solid oxide fuel cells (IT-SOFCs) because it has mixed-conduction characteristics which are electronic and ionic conductivities. It has higher ionic conductivities than other cathode materials for SOFCs such as LSM and LSC. The composite SSC with SDC lowers the thermal expansion mismatch and is effective for extension of the triple phase boundary (TPB). The graded porosity microstructure helps the rate of electrode reaction to increase and make the oxygen gas easy to transport to the active reaction site. In this research, the microstructure was controlled with both compositional and porosity gradient, consisting of fine grains close to the electrode and electrolyte interface, and bigger sizes at the surface of the electrode. As a result, it was proved that the ESD technique can control the graded porous microstructure.