Transport characteristics of water and proton in membrane of PEM fuel cells

Water and proton transport together with water content in proton exchange membrane showed significant effects on the performance of PEM fuel cells. A steady state two-phase flow model is presented to study water transport and water content in the membrane as well as the relation between water content and proton transport resistance. This model couples the conservation of mass, momentum and species equations with transport equation in the membrane. Simulation results indicated that the polarization curves agreed well with experimental data. For the same current density, coefficients of electro-osmotic drag, back diffusion and hydraulic permeation with water content in the membrane increased gradually along the gas flow direction, while net water transport coefficient arid proton transport resistance decreased as operating pressure increased; at the same time electro-osmotic drag, back diffusion, hydraulic permeation and net water transport coefficients and water content in the membrane increased rapidly, while proton transport resistance decreased, which improved the performance of PEM fuel cells.