Stability and performance of La0.6Sr0.4Co0.2Fe0.8O3 nanostructured cathodes with Ce0.8Gd0.2O1.9 surface coating

Abstract

La0.6Sr0.4Co0.2Fe0.8O3-δ is considered as one of the most promising cathodes for Solid Oxide Fuels Cells (SOFCs) operating at intermediate temperatures, however, its performance degrades significantly over time mainly due to phase segregations on the surface. In this work, the surface of La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.8Gd0.2O1.9 (LSCF-CGO) nanostructured cathode is coated with CGO particles via a simple and economic spray-pyrolysis deposition process. The electrode polarization resistance (Rp) and the microstructure evolution of the uncoated and CGO-coated cathodes are investigated by impedance spectroscopy and scanning electron microscopy, respectively. The CGO-coated cathodes exhibit improved stability and performance, with Rp values varying from 0.27 to 0.30 Ωcm2 at an annealing temperature of 600 °C for 400 h. On the contrary, the uncoated cathode shows a faster degradation rate, with a continuous increase of Rp from 2.8 to 8.5 Ωcm2. Above 800 °C, the particle coarsening of the CGO layer results in a significant increase of Rp over time, reaching steady values of 0.04 Ωm2 at 800 °C. An anode-supported cell with the CGO-coated cathode shows a remarkable power density of 0.72 Wcm−2 at 650 °C in comparison to 0.56 Wcm−2 for the cell with uncoated cathode.