Thermal shock resistant composite cathode material Sm0.5Sr0.5CoO3–δ–La0.6Sr0.4FeO3–δ for solid oxide fuel cells

Abstract

The Sm0.5Sr0.5CoO3–δ–La0.6Sr0.4FeO3–δ 1:1 composite, obtained by sintering mixture of components, was tested as a prospective cathode material for the oxygen reduction reaction in solid oxide fuel cells. Catalytic activity of the prepared material was characterized using electrochemical impedance spectroscopy at 400, 450, 500, 550, 600, 650, and 700 °C in oxygen and oxygen-argon mixtures in half-cells with Sm0.2Ce0.8O1.9 as the electrolyte. Relatively low activation energies (65.2, 66.9, and 56.3 kJ mol−1 for PO2/P = 1.0, 0.1, and 0.01, respectively) for the reaction polarization resistance were observed. The specific surface area and the pore distribution were measured by N2 adsorption method. The non-localized density functional theory was used in the analysis of the porosity data. The activity of the prepared composite depended on the pore structure which, in turns, depends on the sintering temperature. The best results were obtained for the composite sintered at the temperature of 1000 °C, where significant decrease in porosity is observed. The series of 53 thermal cycles, consisting of heating to 750 °C and cooling to room temperature confirmed the stability of the composite.