The Stefan–Maxwell model and simple Fick's model type of relations both including Knudsen diffusion for the calculation of species mole fraction distribution inside the porous anode of a solid oxide fuel cell were compared and it was found that at low current densities the models agreed well but as current increased the differences also increase. Based on the findings an empirical correction was proposed for the effective diffusivity used in Fick's model. The corrected diffusivity coefficient gave better agreement with the Stefan–Maxwell model and even at higher current densities the error was less than 5%. This correction was implemented via a three-dimensional solid oxide fuel cell simulation code which uses Fick's model type relations for diffusion flux calculations. The code also takes into account methane steam reforming and water gas shift reactions and the electrochemical oxidation of both H2 and CO.

On Modelling Multi-Component Diffusion inside the Porous Anode of Solid Oxide Fuel Cells Using Fick’s Model. F.N.Cayan, S.R.Pakalapati, F.Elizalde-Blancas, I.Celik: Journal of Power Sources, 2009, 192[2], 467-74