Layered perovskite Sm1−xLaxBaFe2O5+δ as cobalt-free cathodes for IT-SOFCs

Abstract

The cobalt-free layered perovskite oxides Sm_1−xLa_xBaFe₂O_5+δ (x = 0–0.5) (SLBFx, for short) have been systematically investigated to evaluate the feasibility of using them as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). SLBFx powders with an orthorhombic structure were synthesized by the EDTA–glycine combustion method and were observed to be compatible with LSGM and SDC electrolytes below 1250 °C. The electrical conductivities of the SLBFx samples significantly increased with the substitution of La for Sm, with the highest conductivity of 37.8 S cm⁻¹ obtained for the SLBF0.5 sample at 600 °C. Of the La-doped SmBaFe₂O_5+δ series samples, SLBF0.2 displayed the lowest thermal expansion coefficient (TEC) and the minimum electrode polarization resistance, with values of 16.51 × 10⁻⁶ K⁻¹ in the 50–800 °C range and 0.24 Ω cm² at 750 °C, respectively. The anode-supported single cell with SLBF0.2 as the cathode was able to generate a maximum power density of 558 mW cm⁻² at 800 °C in humidified H₂. All things considered, SLBFx materials are good candidates for cobalt-free cathodes in IT-SOFCs.