Segmented distribution of gas diffusion layer porosity and catalyst layer ionomer content in a polymer electrolyte membrane fuel cell

Abstract

Gas diffusion layer porosity and ionomer content inside catalyst layer both can affect cell performance. Electrochemical reaction rate is non-uniform inside the cell. Non-uniform design of components or structures can improve the electrochemical reaction rate distribution and thus promote cell performance. Thus, the investigations on the optimal distribution are done using the optimization solver within COMSOL Multiphysics 5.3a to seek the optimal segmented distribution of porosity or ionomer content to obtain higher current density. The distributions in cathode side along three directions are all investigated. The optimized results show that the porosity increases along main gas flow direction and the ionomer content reduces. With voltage decreasing, the value of porosity around outlet region reduces and the value around outlet region increases, ionomer content shows opposite trend. The porosity under gas channel is higher than that under land. Ionomer content increases under land and reduces under gas channel with voltage decreasing. The porosity is high near catalyst layer and ionomer content near proton exchange membrane is higher at low voltages. The ionomer content distribution along thickness direction can improve current density by 5.596 % at 0.2 V. For better overall cell performance, the porosity changing along x-axis can be selected, the values from under land to under gas channel are 0.384, 0.499, 0.618. These results can provide theoretical guidance for cell components design to obtain higher cell output performance.