The electrocatalytic properties of porous La_0.3Sr_0.7Fe_0.7Cr_0.3O_3−δ electrodes towards oxygen reduction reaction were investigated as a function of temperature, applied cathodic voltage, and electrode thickness by means of electrochemical impedance spectroscopy technique. The impedance spectra were deconvoluted with the aid of an analysis on the distribution function of relaxation times. The electrode polarization was related to the contribution coming from the elementary steps of surface oxygen exchange process. The electrode reaction was appreciably activated by applying cathodic voltage, attributable to reduction of partial transition metal cations in the electrodes accompanied by creation of oxygen vacancies. The electrocatalytic properties displayed a significant dependence on the electrode thickness, which was explained considering the impact of changing electrode thickness on the kinetics of the reaction steps involved. The lengths of electrocatalytically active region were estimated to be 6–12 μm at temperatures from 700 to 800 °C, while the optimum electrode thickness was ascertained to be around 35 μm at the temperatures. The ~ 35-μm-thick electrode showed a polarization resistance of 0.086 Ω cm² at 800 °C. The present study demonstrates that oxygen adsorption and disassociation is the key step dictating the kinetics of the overall electrode reaction.

多孔La _0.3 Sr _0.7 Fe _0.7 Cr _0.3 O _{3− δ}的电催化性能通过电化学阻抗谱技术研究了电极进行的氧还原反应与温度，施加的阴极电压和电极厚度的关系。借助对弛豫时间分布函数的分析，对阻抗谱进行反卷积。电极极化与表面氧交换过程基本步骤的贡献有关。通过施加阴极电压明显激活了电极反应，这归因于电极中部分过渡金属阳离子的还原并伴随着氧空位的产生。电催化性能显示出对电极厚度的显着依赖性，考虑到改变电极厚度对涉及的反应步骤动力学的影响进行了解释。在700至800°C的温度下，电催化活性区域的长度估计为6–12μm，而确定的最佳电极厚度在该温度下约为35μm。厚约35μm的电极的极化电阻为0.086Ωcm²在800°C下。本研究表明，氧的吸附和解离是决定整个电极反应动力学的关键步骤。