Synthesis and characterization of La_0.595V_0.005Sr_0.4CoO_3−δ as a novel cathode material for solid oxide fuel cells (SOFC)

The effect of vanadium doping on the crystal structure and on the electrical, electrochemical properties of La_0.6−x V _x Sr_0.4CoO_3−δ (x = 0.005–0.05) perovskite oxides performing as cathode materials in solid oxide fuel cells is investigated in this study. Crystal structure, surface morphology, and porosity of prepared cathode materials are characterized by X-ray diffraction, X-ray absorption fine structure, and scanning electron microscopy. For the first time, it has been proven by X-ray absorption fine structure that La³⁺ cation is replaced with V^4+/5+ cation in perovskite structure. Since V^4+/5+ cation has the radius almost half of the radius of La³⁺ cation, this replacement adds better properties to the perovskite structure such as ionic conductivity and catalytic activity for oxygen reduction reaction. The electrical conductivity at the intermediate temperatures (400–700 °C) appears to be enough to yield a better performance in intermediate temperature-solid oxide fuel cells applications. The sample with 0.05% V^4+/5+ doping exhibits its maximum electronic conductivity (σ = 843 S.cm⁻¹ at 400 °C) and minimum activation energy (Ea = 0.049 eV). The La_0.595V_0.005Sr_0.4CoO₃ material as electrode for symmetric cell configuration was prepared on both surfaces of yttria-stabilized zirconia substrates. Oxygen concentration related polarization experiment suggests that the oxygen adsorption–desorption process or reactions controlled by the atomic oxygen diffusion process followed by a charge transfer are the cathode reaction rate-limiting steps.

V^4+/5+ ion doped LVxSC (La_0.6-xV_xSr_0.4CoO_3−δ x = 0.005-0.05) cathode materials for intermediate temperature-solid oxide fuel cells (IT-SOFC) are synthesized for the first time by sol-gel method. LV05SC cathode with good electro-catalytic activity for ORR can be considered as a potential cathode material for IT-SOFC applications.