Improved Transport in PEM Fuel Cells by the Introduction of a Structured Macroporous Catalyst Layer

The wide scale implementation of proton exchange membrane (PEM) fuel cell technology has been hindered to a large extent by the high cost associated with the platinum catalyst required for the electrochemical oxidation of protons at the cathode. In low-temperature proton exchange membrane fuel cells, existing cathode catalyst layer designs are plagued by inefficient catalyst utilization due to severe diffusion limitations when operating at medium to high current densities. By introducing a structured network of macropores within the cathode catalyst layer the diffusion limitations caused by liquid water formation can be largely mitigated. These pores allow for continued bulk diffusion of reactants within the thickness of the catalyst layer. It is of interest to determine the optimum macroporous structure within the catalyst layer of a PEM fuel cell.

This work investigates the effects of numerous catalyst layer design parameters on the performance of a PEM fuel cell cathode with structured macroporous channels and nanoporous catalyst regions. These parameters include macroporosity (?mac), catalyst layer thickness (tcl), and platinum loading (mPt). The objective function considered for minimization is the amount of platinum catalyst per Ampere produced by the cell. Preliminary simulation results show that careful manipulation of the cathode catalyst layer microstructure can lead to an order of magnitude improvement of catalyst layer performance.