On the question of MEA preparation for DMFCs

To get information for the development of a continuous MEA fabrication sequence various preparation strategies are investigated. Diffusion layer suspension is made by magnetic stirring, ultrasound mixing and by use of a ball-mill and the slurry is characterised by particle size measurements. The catalytic layers are applied either to the diffusion backing or directly onto the membrane. The latter method yields to improved MEA performance due to the higher utilisation of the catalytic material. Experiments concerning the influence of the anodic diffusion layer thickness and composition show a strong influence on MEA characteristic. For the anodic diffusion layer the influence of the hydrophobicity on methanol transport and CO2 removal is investigated by using PTFE or Nafion© as binder. The Nafion© bonded backing shows better mass transport properties for methanol but CO2 removal becomes crucial at high current densities. Sintering of the PTFE bonded structure improves layer properties for the management of liquid and gas transport. Best results are achieved with sintered PTFE bonded layers with a reduced layer thickness.