Structural Stability and Features of Electrical and Electrochemical Behavior under Reducing

Abstract

In this study, a performance of the complex oxide composition of Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3–δ was investigated from the viewpoint of its use as a fuel or symmetrical electrode for the electrochemical devices with a LaGaO3-based solid electrolyte. The results show that the above-mentioned oxide can be obtained as a single-phase composition using solid-phase synthesis with a final annealing temperature of 1150 °C. It has been shown that the oxide retains satisfactory stability at 800 °C in an atmosphere of 5 % H2 + Ar, only a minor amount, presumably of Co-Fe alloy, has been detected. The electrical conductivity of the oxide in wet hydrogen exhibits a linear semiconductor-type behavior with a conductivity value of 7 S · cm–1 at 800 °C. The polarization resistance of the Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3–δ electrode in wet hydrogen atmosphere reaches approximately 1.09 Ω · cm2 at 800 °C, which is a relatively high value for the electrodes of electrochemical devices. A significant reduction in resistance down to 0.43 Ω · cm2 is observed for the electrode activated with impregnated ceria. It has been demonstrated that the observed decrease in resistance is due to the expansion of the area of the electrochemical reaction without changing its mechanism. The long-term tests with a duration of about 220 h at 800 °C in a wet hydrogen atmosphere demonstrate satisfactory stability of the electrochemical activity of the Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3–δ electrode, which can be considered as a promising electrode for intermediate temperature electrochemical devices, including those of symmetrical design.