Accurate Ex-situ Measurements of PEM Fuel Cells Catalyst Layer Dry Diffusivity

Polymer electrolyte membrane fuel cells (PEMFC) efficiently convert the reaction energy of hydrogen and oxygen to electricity, water and heat. The oxygen reduction reaction occurs on a composite nanostructured catalyst layers (CL) formed from Pt nanoparticles supported on a network of carbon particle agglomerates. Oxygen reaches the reaction site through diffusion. Understanding the diffusion properties of CL is vital to proper design of CL. Measuring the diffusivity of thin porous layers is challenging, as is selecting a suitable substrate and appropriate CL coating procedures.  There are very few CL gas diffusivity experimental studies in the current literature. In this work, CL is coated on 70 μm thick hydrophobic porous polymer substrates with Mayer bar. Diffusivity of CL and the substrate is measured using dry diffusivity test bed and after decoupling diffusivity values are reported for different CL thicknesses.