Modeling of linear sweep voltammetry at porous electrodes using the Bruggeman correlation

At present, electrochemical energy devices are gaining wide attention for facilitating the development of renewable and sustainable energy technologies. To achieve high performance, porous media are commonly used as electrodes of electrochemical devices to develop larger numbers of electroactive sites. However, as materials are limited, the cell performance of these devices needs to be further improved to reduce material costs. Previous studies often modified porous electrodes to enhance cell performance. However, how electrode modifications affect the parameters quantitatively needs clarificaton. Voltammetry is one of the most widely used electroanalytical techniques for evaluating such parameters. Usually, the Nicholson approach or the Randles-Ševčík equation can be used to examine such parameters using voltammetry quantitatively. However, those methods are quantitative approaches to a reaction at a planar electrode in a semi-infinite diffusion space. As a result, these methods are restricted to such systems and cannot be used with porous media. Recent research has sought to account for the effects of a porous structure. However, a specific model for a particular porous media is still required, making parameter evaluation problematic. In this study, a universal model for predicting voltammetric responses of porous electrodes is proposed. The Bruggeman correlation is introduced to account for the effects of the porous structure. The effects of geometric parameters, i.e., the thickness of the electrode, the porosity, and the Bruggeman exponent, on the voltammetric responses were investigated. The results showed the behaviour of the porous electrodes, which cannot be replicated using the conventional model. The findings will benefit those interested in modifying electrodes to improve cell performance.