Gas and liquid mass transport in solid polymer electrolyte fuel cells

Mathematical models are presented for solid polymer electrolyte fuel cells which describe the mass transport limitations which can result at high current density. The models considers oxygen and nitrogen diffusion and convection, vapour and liquid, water transport in the electrode, oxygen transport and water generation at the cathode and water transport through the membrane and vaporisation of water. The direct methanol fuel cell, unlike the hydrogen cell, suffers from mass transport limitations predominantly at the anode. For vapour fed cells the mass transfer characteristics are similar to those for the oxygen cathode, with CO2 flowing counter current to the vaporised fuel. For liquid fed cells mass transfer limitations arise from counter current transport of methanol in the liquid and carbon-dioxide gas. Data for liquid fuel cells is presented and interpreted on the basis of the model.