Performance investigation of proton exchange membrane fuel cells with curved membrane electrode assemblies caused by pressure differences between cathode and anode

Abstract

The membrane electrode assembly (MEA) of a proton exchange membrane fuel cell (PEMFC) would deform when there is a pressure difference between the cathode and anode. In this study, a three-dimensional PEMFC model that incorporates a two-dimensional MEA deformation model is employed to investigate the effects of the curved MEA on oxygen transport, liquid water removal, pressure drops across cells, and resulting overall cell performances. The results show that the MEA deformation generates a gap between the rib and gas diffusion layer (GDL), thereby enhancing the oxygen transport into and liquid water removal from the cathode porous electrode. At an operating voltage of 0.4 V, the output current density is enhanced by 4.83%, 6.67%, and 8.61%, respectively, for the pressure differences of 10, 20, and 30 kPa between the cathode and anode, as compared with that without a pressure difference. An efficiency evaluation criterion (EEC) that represents a tradeoff between mass transfer enhancement and pressure drop penalty is introduced to evaluate the overall cell performance enhancement. The result shows that the EEC value increases with increasing the pressure difference between the cathode and anode, confirming the performance enhancement by the deformed MEA. In addition, the effects of MEA deformation are also examined at two sets of channel heights (H) and widths (W), i.e., WH=0.5 mm and WH=1.5 mm. At an operating voltage of 0.4 V, the output current density is enhanced by 20.18% at a pressure difference of 30 kPa for the cell with WH=0.5 mm, whereas it is improved only by 2.91% for the cell with WH=1.5 mm. Therefore, increasing the pressure difference between the cathode and anode is a more effective approach to performance enhancement for the cell with a small channel height and width.