Co-Deposition and Poisoning of Chromium and Sulfur Contaminants on La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δCathodes of Solid Oxide Fuel Cells

The presence of both chromium and sulfur (Cr/S) contaminants on the microstructure and electrocatalytic activity properties of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) electrodes of solid oxide fuel cells (SOFCs) is studied, using Confocal laser Raman spectroscopy, XRD, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and electrical conductivity relaxation (ECR) methods. LSCF dense bar samples were heat treated in the presence of Cr 2 O 3 and 20 ppm SO 2 and in the temperature range of 600–900°C. The deposition and reaction products between LSCF and Cr/S depend on the temperature: SrCrO 4 only forms on LSCF samples at 900°C and 800°C, while formation of SrSO 4 phase occurs at all temperatures studied. The results indicate that sulfur shows a higher activity with LSCF, as compared to gaseous Cr species. Segregated SrO is more likely to react with gaseous Cr species at higher temperatures, however, reaction with SO 2 is more pronounced at lower temperatures, forming SrSO 4 . ECR results indicate that co-deposition of Cr and sulfur significantly deteriorates the surface exchange and diffusion processes for the O 2 reduction reaction on LSCF electrodes.