Diffusion-Reaction-Conduction Processes in Porous Electrodes: The Electrolyte Wedge Problem

This work studies mathematical issues associated with steady-state modelling of diffusion-reaction-conduction processes in an electrolyte wedge (meniscus corner) of a current-producing porous electrode. The discussion is applicable to various electrodes where the rate-determining reaction occurs at the electrolyte-solid interface; molten carbonate fuel cell cathodes are used as a specific example. New modelling in terms of component potentials (linear combinations of electrochemical potentials) is shown to be consistent with tradition concentration modelling. The current density is proved to be finite, and asymptotic expressions for both current density and total current are derived for sufficiently small contact angles. Finally, numerical and asymptotic examples are presented to illustrate the strengths and weaknesses of these expressions.