Characterization of Sr/Ru co-doped ferrite based perovskite as a symmetrical electrode material for solid oxide fuel cells

The perovskite Sm_0.9Sr_0.1Fe_0.9Ru_0.1O_3-δ(SSFR) is synthesized and investigated as a new type of symmetrical electrode material for solid oxide fuel cells (SOFCs). X-ray diffraction analysis indicates that SSFR exhibits an orthorhombic structure with a space group of Pnma (62). There are no significant changes in polarization resistance (R_p) after a series of experiments in hydrogen and oxygen atmospheres at 800 °C, implying that SSFR has a good redox stability. To get an insight into the rate-limiting steps of SSFR electrode, behavior of R_pis investigated in different oxygen partial pressures (pO₂). Generally, the relationship between R_pand pO₂follows the equation R_p = k(pO₂)⁻ⁿand different n values correspond to different rate-limiting steps. In this study, the n value of 0.5 is obtained for SSFR cathode at high temperature, relating to the diffusion of oxygen atom. In high pO₂, SSFR presents a p-type conducting behavior, with decreasing pO₂, a p–n transition occurs in the range 10⁻¹⁷to 10⁻¹⁸ atm. Additionally, peak power density of the Sm_0.2Ce_0.8O_1.9(SDC, ∼0.6 mm) electrolyte-supported symmetrical cell SSFR|SDC|SSFR achieves 119.69 mW cm⁻²at 800 °C using humidified hydrogen (∼3% H₂O) as fuel.