Investigating electrodes for intermediate temperature polymer electrolyte fuel cell (IT-PEFC): GDL material properties and their influence

One of the ways Polymer Electrolyte Fuel Cells (PEFCs) can be improved is by increasing their operating temperature (>100 oC) [1], commonly known as the Intermediate Temperature PEFC (IT-PEFC) (120 oC) [2]. This allows for the generation of high temperature heat, which allows more facile heat rejection, while simplifying water management as water will exist solely in the vapour phase. In order to optimise these IT-PEFCs, further improvement in the cell components are necessary. A combination of simulation and experimental methods has been used to investigate the material properties of the Gas Diffusion Layer so that ideal parameters can be suggested for intermediate temperature operation. Specifically, the porosity, permeability, electrical conductivity and thermal conductivity were investigated. The influence of the GDL thickness, the Microporous layer and hydrophobic treatment were also studied. Results have shown that the GDL porosity is a key factor of influence on the PEFC electrode. The balance between the mass transport capabilities and the electrical conductivity is very important to the success of the electrode. It was found that the cell performance was most sensitive to the GDL porosity when the cell was in the “standard operating” range of 0.7-0.5 V and that a porosity between 40-60 % was best. The presence of a microporous layer and the hydrophobic treatment improve the MEA performance at intermediate temperature. The thinner GDL showed better performance, which was increased further when operating at higher temperature. The key aspect at high temperature is the balance between water management within the membrane and mass transport in the electrode. In conclusion, the GDL is an integral component of the PEFC, however, the effect of its properties on the MEA performance is not sufficiently understood. In the work presented, it is shown that the MEA performance is sensitive to changes in the GDL porosity and therefore electrical conductivity. The processing of the GDL is still key to MEA performance at intermediate temperature.