Continuum modeling of solid oxide fuel cell electrodes: introducing the minimum dissipation principle

A simple continuum one-dimensional model of porous mixed-conducting electrode applied onto solid oxide electrolyte is proposed and discussed. Assuming linear relationships between the reaction overpotential and current, the model makes it possible to derive analytical solutions for the electrode thickness dependence of the overall electrode resistance. The least dissipation principle is used to determine the distribution of the ionic and electronic currents throughout the mixed-conducting layer. The area-specific resistance is expressed in terms of the electron and ion resistivities of the electrode material, its “reaction resistivity” as a slope of current–overpotential dependence, and geometric parameters. The solution is expanded to describe the electrode impedance and gas transport resistance under DC conditions.