Electrochemical oxygen reduction on LaNi_0.6Fe _0.4O_3-δ film electrode

Electrochemical oxygen reduction on an LaNi_0.6Fe _0.4O_3-δ (LNF) dense film electrode was investigated by using AC impedance spectroscopy as functions of temperature (923∼1073 K), oxygen partial pressure (10^-3∼1 bar), and DC bias (-50∼+20 mV). It was found the oxygen reduction reaction on the LNF electrode is rate-controlled by the absorption and the dissociation of oxygen molecules at the surface, although other elementary reactions also might contribute to the total reaction rate. ¹⁸O isotope exchange and its depth profile measurements by using a secondary ion mass spectrometry (SIMS) were performed to give quantitative analysis for the rate determining step (RDS) on LNF. The conclusion derived from the SIMS measurements was in good agreement with that from the electrochemical measurements, showing that the surface reaction is a major cause of the resistance in the LNF electrode but the bulk diffusion also may contribute to the reaction rate.