Investigation of Oxygen Reduction Reaction on La0.1Sr0.9Co0.8Fe0.2O3-δ Electrode by Electrochemical Impedance Spectroscopy
Investigation of Oxygen Reduction Reaction on La0.1Sr0.9Co0.8Fe0.2O3-δ Electrode by Electrochemical Impedance Spectroscopy
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DOI：
10.1149/2.0581507jes
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发表时间：
2015-01-01
影响因子：
3.9
通讯作者：
Song, Sun-Ju
中科院分区：
文献类型：
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作者：
Im, Ha-Ni;Choi, Moon-Bong;Song, Sun-Ju
采用电化学阻抗谱（EIS）研究了不同氧分压（pO（2））下，在550-650 ℃范围内，La0.1Sr0.9Co0.8Fe0.2O3-delta（LSCF 1982）电极上的氧还原反应（ORR）. EIS数据的弛豫时间（DAT）分析的分布函数使我们能够区分3个单独的子过程，有助于在ORR期间的整体电极极化。在此基础上，利用Gerischer阻抗模型，得到了开路电压（OCV）条件下的氧化学扩散系数（D-chem）和表面交换系数（K-sur）值。在500-650 ℃范围内，K-sur值在10（-5）-10（-8）cm·s（-1）之间，D-chem值在10（-4）-10（-6）cm（2）·s（-1）范围内，由于LSCF 1982的较高离子电导率，其相对高于类似的混合导电LaxSr 1-xCo 1-yFeyO 3-delta（LSCF）。在固定电流负载下，活化过电位的值是分离的，这是很好地拟合Butler-Volmer方程。在电流负载下，交换电流密度（i（0））随pO（2）的变化表明，在高温下，总反应速率由电荷转移反应决定，而在低温下，总反应速率由气体扩散反应决定。(C)2015年电化学学会。All rights reserved.
The oxygen reduction reaction (ORR) on La0 1Sr0.9Co0.8Fe0.2O3-delta (LSCF1982) electrode is investigated by electrochemical impedance spectroscopy (EIS) in 550-650 degrees C range under different oxygen partial pressures (pO(2)). The distribution function of relaxation time (DAT) 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 degrees 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 LaxSr1-xCo1-yFeyO3-delta (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. (C) 2015 The Electrochemical Society. All rights reserved.