Cr deposition on porous La_0.6Sr_0.4Co_0.2Fe_0.8O_{3 - δ} electrodes of solid oxide cells under open circuit condition

The effect of Cr deposition and poisoning on the electrochemical activity and microstructure of La_0.6Sr_0.4Co_0.2Fe_0.8O_{3 - δ} (LSCF) electrodes is investigated in detail under open circuit conditions at 900 °C, 800 °C and 700 °C in the presence of a Fe-Cr alloy interconnect. The electrochemical performance of LSCF electrodes for the O₂ reduction reaction (ORR) under solid oxide fuel cells (SOFCs) mode and for the O₂ evolution reaction (OER) under solid oxide electrolysis cells (SOECs) mode is seriously degraded after exposure to Cr-containing air at open circuit voltage. SEM, XRD and Raman spectroscopy analyses reveal the formation of SrCrO₄ phase and the deposition of a ~ 1 μm thick Cr deposit layer on the outer surface of LSCF electrodes after exposure to Fe-Cr alloy interconnect at 900 °C for 20 h under open circuit conditions, greatly limiting the oxygen exchange and diffusion related processes. However, the magnitude of Cr deposition decreases significantly with the decrease in temperature. The results also confirm that the mechanism of Cr deposition on LSCF electrodes is a chemical process in nature that is initiated most likely by the nucleation reaction between surface segregated SrO_x and gaseous Cr species.