The reduction of Pt loading in cathode catalyst layers (CCLs) of proton exchange membrane fuel cells (PEMFCs) leads to increased local oxygen transport resistance (R_local) through the ionomer-Pt interface on triple phase boundaries (TPBs), as well as poor durability due to key material degradation. This work introduces a stable and accessible porous carbon featuring a graphitized structure as well as optimized pore size of carbon supports, thereby achieving a comprehensive ionomer/catalyst interface. The results show that the graphitization degree of the carbon surface increased significantly after modification, and the slight thermal corrosion facilitates the conversion of micropores into accessible pores between 4–7 nm on carbon surface. The polarization curves exhibit that the peak power density of catalyst based on modified EC300J is 38% higher than the catalyst with conventional carbon supports EC300J (Pt/porous carbon catalyst) under standard operating conditions, and R_local decreased from 0.35 to 0.08 s·cm⁻¹. It is demonstrated that the positively charged carbon surface and optimized pore size on the Fe graphitized carbon supports provide facile and efficient oxygen transport on TPBs. The higher degree of graphitization also provides improved durability, with less performance loss (8.8%) after degradation compared to the baseline electrode (55.2%).

A large-scale industrial application of proton exchange membrane fuel cells (PEMFCs) greatly depends on both substantial cost reduction and continuous durability enhancement. However, compared to effects of material degradation on apparent activity loss, little attention has been paid to influences on the phenomena of mass transport. In this review, influences of the degradation of key materials in membrane electrode assemblies (MEAs) on oxygen transport resistance in both cathode catalyst layers (CCLs) and gas diffusion layers (GDLs) are comprehensively explored, including carbon support, electrocatalyst, ionomer in CCLs as well as carbon material and hydrophobic polytetrafluoroethylene (PTFE) in GDLs. It is analyzed that carbon corrosion in CCLs will result in pore structure destruction and impact ionomer distribution, thus affecting both the bulk and local oxygen transport behavior. Considering the catalyst degradation, an eventual decrease in electrochemical active surface area (ECSA) definitely increases the local oxygen transport resistance since a decrease in active sites will lead to a longer oxygen transport path. It is also noted that problems concerning oxygen transport caused by the degradation of ionomer chemical structure in CCLs should not be ignored. Both cation contamination and chemical decomposition will change the structure of ionomer, thus worsening the local oxygen transport. Finally, it is found that the loss of carbon and PTFE in GDLs lead to a higher hydrophilicity, which is related to an occurrence of water flooding and increase in the oxygen transport resistance.