Modeling Cyclic Voltammetry at Porous Electrodes Using the Bruggeman Relation

Currently, the major global problems are climate change and global warming. There have been many attempts to switch the use of fossil fuels to renewable energy. In the future, a large proportion of power will be generated from renewable energy. Consequently, electrochemical energy storage and conversion devices such as secondary batteries and fuel cells will play a significant role. These energy storage and conversion devices typically use porous electrodes due to their high surface area per volume. A large surface area means a large surface area reacts and generates a large amount of electric current in a limited space. In the past, many studies have tried to improve the electrode structure to reduce the losses incurred within the electrode. However, it is known that electrode modification by methods such as heat treatment and electrochemical corrosion treatment can improve the performance of electrochemical devices. However, to date, it is still challenging to quantitatively assess the magnitude of the improvement in the fundamental parameters. 

One of the most widely used electroanalytical techniques for evaluating such parameters is cyclic voltammetry. Conventionally it was understood that surface area and reaction rate constant affect differently to the responses, allowing the two parameters to be evaluated independently. However, the voltammetric response is complex, and many factors can distort the response, such as the shape of the electrode and the electrical current generated by the double layers. This makes conventional methods insufficient for evaluating such parameters from a complex response. The researchers initially solved the problem by limiting the electrodes used in the cyclic voltammetry to electrodes of a simple shape (planar and cylinder). This makes it challenging to improve the performance of electrochemical devices because not all materials can be easily fabricated into such forms. Although groups of researchers attempted to solve the problem by trying to predict voltammetric responses at porous electrodes, they still have to use different models depending on the geometrical shape of the pore inside porous electrodes. Therefore, the main goal of this study was to develop a general model for predicting cyclic voltammetry at porous electrodes. The model will be developed based on the porous model and can be used to evaluate parameters quantitatively without considering the geometric structures that may differ for each porous electrode. The results of this research project eliminate the need for specific models for each porous medium, which will be beneficial for the characterization of voltammetric responses. In the future, it can also be extended to be implemented as a model in commercial software. This will enable researchers worldwide to understand electrode modification's impact and develop better electrochemical devices to facilitate the transition to a renewable energy society.