Modeling Distributed Charge-Transfer Processes in SOFC Membrane Electrode Assemblies

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 me-dia 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 re-gion 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.