To improve Proton Exchange Membrane Fuel Cells (PEMFC) performances, phenomena occurring in operating conditions must be understood. This work investigates the influence of PTFE (PolyTetraFluoroEthylene) loading in cathodic active layers on the global PEMFC performance and more precisely on diffusive limitations. As they display a controllable pore texture, carbon aerogels may replace advantageously the usual carbon blacks as catalyst support in cathodes. Resulting Membrane Electrode Assemblies (MEA) are evaluated on a monocell test bench. This study shows that PTFE influences greatly PEMFC performances and diffusive limitations as it evacuates the water produced at the cathode. These results highlight that diffusive limitations must be controlled and that PTFE loading must be optimized.