High performance of SrCo1-xZrxO3-δ perovskite cathodes for IT-SOFCs

Abstract

Stabilization of a tetragonal perovskite structure in the SrCoO3-δ system at room temperature has been achieved through wet chemical techniques, and it has been successfully tested in Solid Oxide Fuel Cells (SOFCs). Chemical substitutions at the Co position were carried out by introducing different amounts of zirconium (SrCo1-xZrxO3􀀀 δ; x = 0.05, 0.08 and 0.11) to destabilize the columns of CoO6 octahedra sharing faces in the competitive 2H-hexagonal phase. The crystal structure was studied by X-ray diffraction (XRD) and neutron powder diffraction (NPD) at 25 ◦C and correlated with mechanical and electrical properties. Chemical compatibility studies between the samples and the La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) electrolyte revealed not interaction at high temperatures. Dilatometric analysis measurements showed a compatible thermal expansion with the LSGM electrolyte over the entire temperature range, demonstrating good mechanical compatibility. Furthermore, the relatively high conductivity values (~83 S cm-1 at 850 ◦C) indicated their suitability as cathodes in SOFCs. Finally, test cells prepared with an electrolyte (LSGM) supported configuration provided a maximum output power exceeding 600 mW/cm2 using pure H2 as fuel at 850 ◦C. Importantly, the performance of the cathode materials did not degrade after extended operation at this temperature.