The oxygen reduction reaction (ORR) on La 0.1 Sr 0.9 Co 0.8 Fe 0.2 O 3-δ (LSCF1982) electrode is investigated by electrochemical impedance spectroscopy (EIS) in 550-650 • C range under different oxygen partial pressures (pO 2 ).The distribution function of relaxation time (DRT) analysis of EIS data enabled us to distinguish 3 individual sub-processes contributing toward the overall electrode polarization during ORR.Based on these results, oxygen chemical diffusivity (D chem ) and surface exchange coefficient (K sur ) values are obtained under open circuit voltage (OCV) conditions by Gerischer impedance model.In 500-650 • C range, K sur values ranges between 10 -5 -10 -8 cm•s -1 and D chem values are in 10 -4 -10 -6 cm 2 •s -1 range which, due to the higher ionic conductivity of LSCF1982, is relatively higher than those for similar mixed-conducting La x Sr 1-x Co 1-y Fe y O 3-δ (LSCF).The values of activation overpotential are separated under the fixed current load, which are well-fitted to the Butler-Volmer equation.Under the current load, the variation of exchange current density (i 0 ) with pO 2 indicated that at the high temperature the total reaction-rate is determined by charge transfer reaction, but when temperature is decreased the reaction-rate is determined by the gas diffusion reaction.
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Im et al. (2015) studied this question.
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