Effects of sigracet® gas diffusion layers, with different porosity and hydrophobic agent, on the performance of low platinum loading pem fuel cells

Abstract

This thesis studied the performance of low platinum loading proton Exchange membrane fuel cells that were fabricated using the inkjet printing method and assembled with four different types of SIGRACET® gas diffusion layers (28 BC, 29BC, 28 BA and 29BA). The performance was study based on the results obtained from polarization curves, cyclic voltammetry and limiting current experiments. As the major voltage losses of low Pt-loading proton exchange membrane fuel cells are on the mass transport region because of wáter management problems, the addition of micro porous layers on the gas diffusion layers can prevent the flooding of the cell because of the presence of a hydrophobic agent on the micro porous layer. The differences between the gas diffusion layers tested are porosity (28-29) and the presence of a hydrophobic agent (BA-BC). The obtained results suggest that the presence of a micro porous layer on the gas diffusion layer is predominant when comparing the performance of the cells with 28BC and 29BC gas diffusion layers, therefore the porosity in this type of gas diffusion layers does not affect much the performance. On the other hand, the gas diffusion layers without micro porous layer, the BA series, show great difference on the performance, being the cell with the gas diffusion layer 28BA with an excellent performance, even better than the BC series, reaching up to 4 A/cm2 at wet conditions. However, the 29BA gives the worst performance. Despite the outstanding performance obtained with the 28BA, the lack of a micro porous layer on the gas diffusion layer led to a huge crossover because of the carbon fibers intrusion into the catalyst coated membrane. In addition, an improvement on the fabrication process of the cell was achieve adding a drying time of 90 seconds between each layer during the inkjet printing, which allowed reducing the cracks generated on the catalyst coated membrane.