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 in 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 and operation of CL and PEMFC. Measuring the diffusivity of thin porous layers is challenging, as is selecting a suitable substrate and appropriate CL coating procedures. In this work, CL is coated on 70 μm thick hydrophobic porous polymer substrates with a Mayer bar coater. Several samples are prepared and their thickness are measured accurately. The diffusivity of the CL and the substrate are measured using a dry diffusivity test bed and the resulting CL-diffusivity values are determined for different Pt loadings.