Electrochemical properties of lanthanum strontium aluminum ferrites for the oxygen reduction reaction

The oxygen reduction reaction was studied on the La1−xSrxAlyFe1−yO3 (x=0.2, y=0.1, 0.2, 0.3, 0.4) system by cyclic voltametry and electronic conductivity. Activation energies for the bulk and film conductivities were determined. Tafel analysis afforded the activation energies “from the temperature dependence of the exchange current densities” as well as the charge transfer coefficient. The electrical conductivity of bulk material was found to decrease with aluminum content. Formation of the materials into thin porous films further decreased the conductivity after correcting for porosity. Aluminum substitution substantially decreased the performance through influence of the pre-exponential factor in the Butler–Volmer formulation. Neither the activation energies nor the charge transfer coefficient for these materials varied significantly. Aluminum does not adversely influence the basic mechanism of oxygen reduction. It may occupy and block electrochemically active sites on the electrode surface, but it does not appear to decrease the intrinsic activity of available surface sites.