Experimental probing of effects of carbon support on bulk and local oxygen transport resistance in ultra-low Pt PEMFCs

Carbon support not only promises to dispersedly anchor Pt-based metal nanoparticles but also functions as the critical component of catalyst layers (CLs) in polymer electrolyte membrane fuel cells (PEMFCs). Thus, the geometrical and surface properties of carbon support are believed to impact the mass transport greatly, especially the local oxygen transport in ultra-low Pt PEMFCs. Herein, we explore influences of carbon support on oxygen transport resistance in cathode catalyst layers (CCLs) through combining the limiting current method with a dual-layer CCL design. Results demonstrate that the properties of carbon support have a more significant effect on the local oxygen transport resistance relative to the bulk one. Based on various advanced physicochemical characterizations, it is analyzed that the geometrical morphology of carbon support influences the bulk oxygen transport resistance via featuring the pore structure in the electrode, while the surface functional groups of carbon support influence the local oxygen transport resistance via determining the distribution of ultra-thin ionomer films on the catalyst surface. It is believed that the findings on the interaction between carbon support and cathode mass transport behavior give a critical enlightenment on the design of high performance ultra-low Pt membrane electrode assemblies (MEAs).