THEORETICAL BASICS OF MONITORING THE CONDITION OF THE ELECTRODES OF CHEMICAL CURRENT SOURCES BY THE METHOD OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

Oleg Ryabokin
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Abstract

On the basis of the conducted critical review of modern physical models of the porous electrode, it сan be stated that under the conditions of non-uniform mass transfer taking into account the depth of the electrode, it is possible not only to develop new porous electrodes for a certain application, but also to control the state of electrochemical systems as a whole using the non-destructive method of electrochemical impedance spectroscopy. The presence of a macroscopic model of porous electrode allows one to use the integration of parameters over the surface of the electrode and obtain the average values of current, resistance and capacity within the electrode using the method of averaging in the volume ele­ment within the electrode, where porosity is the volume fraction of the void within the element, which is filled with electrolyte solution. This is the theoretical basis for using electrochemical impedance spectroscopy to assess the state of electrodes in electrochemical current sources. To take into account the influence of the aqueous electrolyte, it is possible to use a model taking into account the area of the effective wetted surface, which makes it possib­le to relate the wetting of the electrode pores with the electrolyte solution to the change in electrical conductivity and polarization of the electrode surface. In this case, when usingelectrochemical impedance spectroscopy, it is possible to obtain information about the following changes in primary current sources: 1– the effect of temperature, which leads to a decrease in the areas of the electrode wetted by the electrolyte, which affect the value of the capacity of the DEL, 2 – chemical processes that lead to the destruction of hydrophilic pores and pores with hydrophilic-hydrophobic walls, an increase in the hydrophobic component on the surface of the electrode, 3 – mechanical destruction of the electrodes. The use of models that take into account the geometry of pores makes it possible to obtain correct data for the analysis of the porous surface in the presence of an electrolyte and in cases of gas phase adsorption in presence of closed pores, as well as to use the value of the capacity on the surface of electrodes to assess the state of their performance.
用电化学阻抗谱法监测化学电流源电极状态的理论基础
在对多孔电极的现代物理模型进行批判性回顾的基础上,可以指出,在考虑电极深度的非均匀传质条件下,不仅可以开发出用于特定应用的新型多孔电极,而且可以利用电化学阻抗谱的非破坏性方法来控制整个电化学系统的状态。多孔电极宏观模型的存在允许人们使用电极表面参数的积分,并使用电极内体积元的平均方法获得电极内电流,电阻和容量的平均值,其中孔隙率是元件内空隙的体积分数,其中充满了电解质溶液。这是利用电化学阻抗谱评价电化学电流源中电极状态的理论基础。为了考虑到水电解质的影响,可以使用考虑有效润湿表面面积的模型,这使得将电极孔隙与电解质溶液的润湿与电极表面的电导率和极化变化联系起来成为可能。在这种情况下,当使用电化学阻抗谱时,可以获得有关一次电流源的以下变化的信息:1 -温度的影响,导致电极被电解液润湿的面积减少,从而影响DEL的容量值;2 -化学过程导致亲水孔和具有亲疏水壁的孔被破坏,电极表面疏水成分增加;3 -电极的机械破坏。使用考虑到孔隙几何形状的模型,可以获得正确的数据,用于分析存在电解质和存在封闭孔隙的气相吸附情况下的多孔表面,以及使用电极表面的容量值来评估其性能状态。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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