Development of a numerical SOFC cathode model

A cathode model, suitable for incorporation into planar solid oxide fuel cell stack performance models, has been developed. Mechanisms considered in the formulation include mass transfer from the gas channel to the electrode surface, gaseous (bulk and pore) diffusion through the porous electrode, adsorption of oxygen onto active sites at the cathode/electrolyte interface, and electrochemical reduction of the adsorbed oxygen. The reaction step is assumed to be rate limiting with the adsorption step in equilibrium. Fick`s law is used to model the diffusion step with the adsorption step represented by a n-site Langmuir adsorption isotherm. The Butler-Volmer equation is used to describe the charge transfer process. Model parameters have been determined by optimization against published data. For co-flow arrangements, performance of the cell near the fuel inlet is limited by diffusion.