Electrochemical impedance simulation of porous electrodes with variously shaped pores using 3-dimensional finite element method

Abstract

Porous electrodes are widely used in many applications, such as enzyme electrodes, energy devices, and electrosynthesis. However, evaluation of porous electrodes using electrochemical impedance spectroscopy, one of the most promising methods for determining electrochemically relevant structural information, is challenging. Thus, in this study, impedance spectra were simulated using a three-dimensional, finite element method-based model for porous electrodes. The shape of the electrode pore was varied, and the effect on the resulting impedance spectrum was analyzed. The results indicated that for certain pore shapes, such as wide and shallow cylinders, a three-dimensional model was required to obtain accurate results. However, for narrow and deep cylindrical pores, a classical one-dimensional approximation was sufficiently accurate, and a 45º inclined line was observed in the impedance spectra with high frequencies, even when a three-dimensional model was employed. Moreover, wide and shallow or narrowing pores result in a higher inclination angle, whereas widening or branching pores result in a lower inclination angle. These features were also observed when charge transfer and diffusion processes were considered in terms of a mediator-type enzyme electrode reaction.