A stability study of impregnated LSCF–GDC composite cathodes of solid oxide fuel cells

• Performance and microstructure of nano-structured LSCF–GDC cathodes are studied in detail.
• Agglomeration of infiltrated LSCF nanoparticles is responsible for the performance degradation.
• Surface composition change could also contribute to the degradation in the electrochemical activity of the cathodes.
• Addition of MgO or LNF phase effectively inhibit the agglomeration of LSCF nanoparticles.

The performance degradation of composite cathodes of La0.6Sr0.4Co0.2Fe0.8O3−δ and Gd-doped ceria (LSCF–GDC), prepared by impregnating the porous GDC scaffold with a nitrate solution containing La, Sr, Co and Fe in desired composition, is investigated at 750 °C and open circuit in air for 500 h. The performance of the impregnated LSCF–GDC composite cathodes deteriorates after testing at 750 °C for 500 h; the electrode polarization resistance (Rp) increases from 0.38 to 0.83 Ω cm2, and the electrode ohmic resistance (Ro) increases from 1.79 to 2.14 Ω cm2. The grain growth and coarsening of impregnated LSCF nanoparticles are responsible for the performance degradation of the cathodes. XPS analysis shows the enrichment of cobalt on the surface of the infiltrated LSCF–GDC cathodes and such surface segregation could also contribute to the degradation of the electrocatalytic activity of the cathodes. Introducing MgO and LaNi0.6Fe0.4O3 phases can effectively suppress the coarsening of LSCF nanoparticles and enhance the stability of the cathodes. However, the enhancing effect is related to the conductivity and electrocatalytic activity of the introduced phases.