Electrochemical performance of La0.6Sr0.4Co0.2Fe0.8O3–Ce0.9Gd0.1O2-δ composite SOFC cathodes fabricated by electrocatalyst and/or electrocatalyst-ionic conductor infiltration

Abstract

Infiltration of electrocatalyst precursor solutions into previously sintered porous ionic conductor scaffolds has been used recently as an alternative method to the conventional co-sintering route to fabricate electrocatalyst-ionic conductor composites for solid oxide fuel cell (SOFC) cathode applications. However, the aqueous nitrate solutions generally used to perform the infiltration process results in electrocatalyst precipitates that are disconnected from each other, yielding poor electrode performance. In this work, polymeric electrocatalyst (La0.6Sr0.4Co0.2Fe0.8O3—LSCF) precursors that produce interconnected thin films upon heat treatment were used to infiltrate porous ionic conductor Ce0.9Gd0.1O2-δ (GDC) scaffolds to overcome these issues. In addition, for the first time in the literature, a mixture of LSCF and GDC polymeric precursors, which would yield LSCF–GDC nanocomposite coatings on the grains of the porous GDC scaffold were used as the infiltration solution. Thus, further enhancement of the electrocatalyst/ionic conductor interfacial area and achievement of improved electrode performance was aimed. As a result of the optimization studies, the lowest measured area specific polarization resistance (ASRcathode) values of 0.47 and 0.73 Ω.cm2 were obtained for polymeric LSCF+GDC and LSCF precursor infiltrations respectively at 700 °C, in air. In addition, LSCF+GDC infiltration yielded electrodes with much improved long-term stability in comparison to those obtained by LSCF infiltration.