Modeling Polarization Losses in HTPEM Fuel Cells

A numerical model for simulating the distributed charge transfer in HTPEM is presented. The electrodes are discretized along its thickness and the model resolves the species composition, mixture density, and the ionic and electronic potential. The rate of hydrogen oxidation and oxygen reduction reactions is derived based on rate limiting assumptions applied to a set of elementary single-electron transfer reactions. Subject to the rate determining step chosen the derivation results either in Butler–Volmer-type or non-Butler–Volmer-type rate expressions. The form of exchange current density is a result of derivation and depends on the concentration of reactants and products. The order of the rate depends on the symmetry factor for charge transfer reaction. The model is validated by reproducing experimentally measured cell polarization data and activation losses.