Modeling Distributed Charge-Transfer Processes in Membrane Electrode Assemblies with Mixed-Conducting Composite Electrodes

Abstract

A model is developed to represent chemistry and transport in a membrane- electrode assembly with porous mixed ionic-and-electronic conducting composite electrodes. Reactive porous media transport within electrodes is represented with a Dusty-Gas model. Charge-transfer chemistry is handled via a modified Butler- Volmer formalism, which depends on the local electric-potential differences. Heterogeneous chemistry (e.g., reforming or partial oxidation) is handled via a detailed surface-reaction mechanism. For typical composite- electrode structures the charge-transfer region extends about 10 to 20 microns from the dense electrolyte. The model is formulated as continuum differential equations, which are solved computationally on a discrete mesh network.