Fabrication of composite cathodes by electrodeposition for solid oxide fuel cells

Cobaltite-based perovskites (CBPs) such as LSC, SSC, LSCF and BSCF have been studied as promising cathode materials for intermediate temperature solid oxide fuel cells (SOFCs) due to their high mixed ionic and electronic... [ view full abstract ]

Cobaltite-based perovskites (CBPs) such as LSC, SSC, LSCF and BSCF have been studied as promising cathode materials for intermediate temperature solid oxide fuel cells (SOFCs) due to their high mixed ionic and electronic conductivity and high activity for oxygen reduction reaction. However, CBPs form insulating phases with YSZ during conventional high temperature sintering. To avoid the high sintering temperatures, the CBPs are usually infiltrated into a back bone of YSZ. But the infiltration is a tedious process as many infiltration cycles might be required to achieve a desired perovskite loading. Another technique that can be used to fabricate nanostructured cathodes for SOFCs is electrodeposition. Electrodeposition gives significant advantage over the infiltration technique as a higher catalyst loading can be achieved in a single step.

In this work a new process is being developed to fabricate high surface area electrodes for SOFCs by electrodeposition onto carbon nanofibers template that had been grown onto a porous ion conducting scaffold (ICS). Anode supported half cells (NiO-YSZ|NiO-SSZ|SSZ) were fabricated by uniaxial pressing and pre-sintering of NiO-YSZ powders, followed by dip-coating of NiO-SSZ anode functional layer and SSZ electrolyte layer and finally sintering at 1400 °C. Porous ICSs were fabricated onto the dense SSZ electrolyte by screen printing and sintering of an ink containing SSZ, GDC and PMMA powders. The carbon nanofibers were grown onto the ICS by thermal chemical vapor deposition of carbon atoms by using C₂H₄ as a source of carbon. The images taken by a scanning electron microscope (SEM) revealed the formation of carbon nanofibers grown randomly onto the porous ICS. Moreover, LaCoO₃ (LCO) was successfully electrodeposited onto the carbon deposited ICS. The morphology of LCO deposition was observed to be similar to that of carbon nanofibers template. Energy dispersive X-ray spectroscopy (EDS) showed an average of 25 weight percent of LCO deposited throughout the cross section of porous ICS. Also, the elemental composition of lanthanum and cobalt was found to be stoichiometric for the formation of a pure LCO perovskite phase.