Investigation of Sc doped Sr2Fe1.5Mo0.5O6 as a cathode material for intermediate temperature solid oxide fuel cells.

In this work we show that the performance of a Sr 2 Fe 1.5 Mo 0.5 O 6 cathode can be improved by scandium substitutional doping. Herein Sr 2 Fe 1.5-x Sc x Mo 0.5 O 6 (SFSc x M) compounds are synthesized with a doping value (x) varying from 0 to 0.2, using a glycine-nitrate combustion progress. The phase structure and morphology are characterized by X-ray powder diffraction and scanning electron microscopy showing a perovskite structure and a porous microstructure when doping between 0 and 0.1. X-ray photoelectron spectroscopy results indicate that the Sc-doping has a clear effect on Fe 2+ /Fe 3+ and Mo 6+ /Mo 5+ ratios. On cells consisting of SFSc x M electrodes and La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 electrolytes, Sc doping is found to be very effective in reducing the interfacial polarization resistance. Impedance data analysis of SFSc 0.05 M cathode at a variety of oxygen partial pressures indicates that the rate limiting steps are the dissociation of adsorbed molecular oxygen for the high-frequency arc and the migration of oxygen ions to the triple phase boundary for the low-frequency arc, respectively. The highest single cell peak power density is obtained with the SFSc 0.05 M cathode reaching 1.23 W cm −2 at 800 °C. The results suggest that Sc-doping of SFSc x M can substantially improve the electrochemical performance. [ABSTRACT FROM AUTHOR]