Oxygen Reactions at LaSrMnO3/Yttria-Stabilized Zirconia (LSM/YSZ) Interfaces

The focus of this paper is the establishment of reliable methods for the determination of the mechanism and kinetics of the oxygen reduction reaction (ORR) at LSM/YSZ interfaces. Techniques used include cyclic voltammetry (CV) and ac impedance methods over a temperature range from 600 to 100°C. The exchange currents for the ORR, determined both from the low and high field CV data and the charge transfer resistance from ac impedance, agree closely and yield an apparent activation energy of ca. 120 kJ/mol. The Tafel slopes for the ORR at composite LSM/YSZ electrodes were found to be substantially higher than predicted, based on normal mechanistic considerations and assuming a symmetry coefficient of 0.5. This may be the result of the adsorption of reaction intermediates in a porous electrode matrix.