Mixed conductivity and electrocatalytic performance of SrFeO3-δ–SrAl2O4 composite membranes

Oxygen-ionic and electronic transport in dense (SrFe)1−x(SrAl2)xOz composites, consisting of strontium-deficient Sr(Fe,Al)O3-δ and SrAl2O4 phases, is determined by the properties of perovskite-like solid solution. Increasing the content of SrAl2O4, with a total conductivity as low as 5 × 10− 7 − 10− 5 S × cm− 1 at 973–1273 K in air, results in the gradual decrease of the partial conductivities, but also enables the suppression of thermal expansion. Compared to single-phase SrFe1−xAlxO3-δ, (SrFe)1−x(SrAl2)xOz composites exhibit enhanced thermomechanical properties, while the oxygen permeability of these materials has similar values. The composite membranes exhibit stable performance under air/(H2–H2O–N2) and air/(CH4–He) gradients at 973–1173 K. The oxidation of dry methane by oxygen permeating through (SrFe)0.7(SrAl2)0.3Oz results in dominant total oxidation, suggesting the necessity to incorporate a reforming catalyst into the ceramic reactors for natural gas conversion.