Generalized modified Poisson–Nernst–Planck model for electrical double layer with steric, correlation and thermal effects applied to fuel cells

Abstract

In this work, the electrical double layer (EDL) formed at the electrode/electrolyte interfaces in a proton exchange membrane fuel cell (PEMFC) is modeled using a Generalized Modified Poisson–Nernst–Planck model. The model includes a limited number of parameters, such as the Debye length, the correlation factor, the size of the ions and the temperature. The latter is particularly relevant, as it affects the Debye length and consequently the thickness of the EDL. The set of equations is written in dimensionless form, is discretized by the finite difference method and integration is performed by the three-stage Simplified Runge–Kutta method. The results obtained for the EDL exhibit a similar behavior as the Gouy–Chapman analytical solution for flat surfaces and an asymptotic solution in spherical coordinates when the radius of the sphere is much greater than the Debye length. The analysis of the EDL contributes to improve the understanding of the behavior of the reactive flows that occurs within a PEMFC and which have a crucial effect on the latter’s performance.