Improved Cathode Catalyst Layers for Proton Exchange Membrane Fuel Cells

Abstract

In this work we show how two different catalyst layer fabrication techniques can improve the PEM fuel cell performance by introducing macro porosities in the layer. In the first technique, a template with 4 μm diameter pillars made using photo lithography is pressed against the cathode side of Gore® Primea® MEA to create evenly distributed macro pores/channels. In the other technique, mono-dispersed polystyrene particles with 1 μm diameter were used as pore formers to obtain homogeneously distributed macropores in the cathode catalyst layer. These MEAs were made in-house with the cathode catalyst layer thicknesses of about 1 μm. Fuel cell testing carried out on these two types of modified MEA structures with lower Pt utilization show a reasonable improvement in the cell performance at higher current densities. The improved performance at high current densities could be attributed to the presence of macro porosities in the catalyst layer, which enhance the mass transport properties of the catalyst layer.

Tailored porosities of the cathode layer for improved polymer electrolyte fuel cell performance

“…This would facilitate a more uniform and rapid distribution of oxygen and product water than in a fully nanoporous layer. There is not yet such general procedure adopted in the production of MEAs, and the present work, along with our recent publication [14], can be seen as first steps in this direction. We have chosen to investigate the effect on the cathode where the potential for improvements are largest.…”

“…The schematic preparation process of a paste for the catalyst layers was described in our previous publication [14]. A conventional anode was used, to be able to conclude on the cathode performance directly.…”

“…To use indentation techniques, templates etc. is close at hand [11,12,14], but these procedures are costly and cumbersome at their present stage of development. We ourselves were struggling to fabricate catalyst layers with pores <2 mm through template-assisted indentation methods [14]).…”

“…is close at hand [11,12,14], but these procedures are costly and cumbersome at their present stage of development. We ourselves were struggling to fabricate catalyst layers with pores <2 mm through template-assisted indentation methods [14]). The theoretical results mentioned above are useful in this situation, as they make clear that the exact value of the macroporosity, as well as the pore shape is not essential for achieving improvements.…”

“…For this reason, we have turned our attention to the possibility offered by polystyrene monodisperse particles [14]. The fact that they are monodisperse means that we can determine the volume fraction of macropores that they can introduce in the catalyst layer.…”