Perspectives on Challenges and Achievements in Local Oxygen Transport of Low Pt Proton Exchange Membrane Fuel Cells

Abstract The key to address the cost issue of polymer electrolyte membrane fuel cells (PEMFCs) lies on reducing Pt amount employed in cathode catalyst layers (CCLs). In past decades, researchers focus on developing series of alloy and core–shell electrocatalysts with high oxygen reduction reaction activity in order to alleviate the low Pt loading caused performance loss. However, it is noted that the concentration polarization loss resulting from the cathode oxygen transport plays a more important role as the Pt loading decreases, especially the local oxygen transport through the ultrathin ionomer film covering on Pt surface. This paper reviews the nanomorphology of the ultrathin perfluorinated sulfonic acid ionomer film in CCLs, as well as the local oxygen transport mechanism and the corresponding effects on fuel cell performance in low Pt PEMFCs. In addition, both the detailed local oxygen transport properties in carbon black‐supported Pt membrane electrode assemblies (MEAs) and high surface carbon‐supported MEAs are summarized. Subsequently, numerous innovative strategies and effective approaches of reducing the local oxygen transport resistance are introduced. The new insights proposed in this paper have important implications for enhancing local oxygen transport and designing high‐performance fuel cell electrodes.