Influence of pore-size distribution of diffusion layer on mass-transport problems of proton exchange membrane fuel cells

The influence of pore-size distribution of the diffusion layer on mass-transport problems of proton exchange membrane fuel cells (PEMFCs) is investigated using electrodes with hydrophobic diffusion layers for which the pore-size distribution is designed by pore-former and heat treatment. It is confirmed that the pore-size distribution of the diffusion layer is a more critical parameter for mass-transport processes within the electrode and for cell performance characteristics than the total porosity itself. Data obtained from mercury intrusion porosimetry, single-cell performance tests and ac impedance analyses indicate that the performance loss due to mass-transport limitations can be reduced by enlarging the macropore volume in the diffusion layer. The water flooding problem is discussed in terms of condensation phenomena which are dependent on pore-size.