Perovskite-type La0.6Sr0.4Co0.2Fe0.8O3, Ba0.5Sr0.5Co0.2Fe0.8O3, and Sm0.5Sr0.5Co0.2Fe0.8O3 cathode materials and their chromium poisoning for solid oxide fuel cells

In the pursuit for solid oxide fuel cell (SOFC) cathode materials that can operate over a wide temperature range, especially at low temperatures such as 600 °C, perovskite structure materials La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Ba0.5Sr0.5Co0.2Fe0.8O3 (BSCF), and Sm0.5Sr0.5Co0.2Fe0.8O3 (SSCF) are studied. Their electrochemical performance is compared by electrochemical impedance spectroscopy (EIS) at 600 °C, 700 °C and 800 °C for 100 hrs through an AISI 441 interconnect/cathode/yttria-stabilized zirconia (YSZ) electrolyte half-cell structure. The BSCF cathode has the smallest polarization resistance at 600 °C, closely followed by the SSCF cathode; the LSCF cathode has the smallest polarization resistance working at 700 °C; the SSCF cathode has the smallest polarization resistance working at 800 °C, closely followed by the LSCF cathode. From 600-800 °C, SrCrO4 phase forms on the SSCF cathodes near the interconnect while BaCrO4 phase forms on the BSCF cathodes near the interconnect. For the LSCF cathodes, however, SrCrO4 phase is only detected at 700 °C and 800 °C. Cr species diffusion to and poisoning of the cathodes do not directly correlate with the half-cell performance. Lattice constant, stoichiometry, particle size, Cr deposition, and working temperature are important factors to consider.