The mechanical properties of gas diffusion layers (GDLs) in proton exchange membrane fuel cells (PEMFCs critically govern compression-dependent transport phenomena that control local performance and durability. This work presents a systematic, self-consistent characterization of orthotropic mechanical behavior, through-plane (TP) thermal and electrical conductivities, in-plane (IP) gas permeability, and structural properties for five commercial GDLs—wet-laid carbon papers (Toray TGP-H-060 with 5 and 30 wt% PTFE; SGL 29BA uncoated; SGL 28BC MPL-coated) and one hydroentangled non-woven (Freudenberg H23C7)—measured under controlled compressive loads (0.5–3 MPa). Additional GDL materials are benchmarked against literature data. Increased PTFE content significantly stiffens the fibrous network, while microporous layer (MPL) addition introduces additional through-plane bulk transport resistance. In-plane gas permeability decreases by approximately 70–90% over the investigated compression range for all materials, with the most pronounced reductions (up to two orders of magnitude) observed in SGL 28BC due to pronounced MPL intrusion into the substrate, forming a mixed fiber–MPL zone that reduces lateral macropore connectivity and increases flow resistance. Physically motivated models are applied to interpret the observed trends. Effective percolation theory correlations describe the nonlinear evolution of thermal and electrical conductivities with solid volume fraction, yielding interpretable parameters that explain material class differences and thermal − electrical decoupling. In addition, a hyperelastic two − power-law strain energy framework that mechanistically captures the full compressive response − from initial fiber bending, through topology-controlled stiffening, to high-strain densification − while maintaining thermodynamic consistency and finite-element compatibility is proposed. While Toray TGP-H-060 is extensively benchmarked in the literature, coupled compression-dependent multi-property datasets remain scarce for hydroentangled non-woven GDLs and MPL-coated roll-good grades. The comprehensive dataset and modeling framework presented here provide a robust foundation for high-fidelity three-dimensional PEMFC stack simulations, enabling improved material selection, stack design, and performance and durability optimization.

The integration of proton exchange membrane fuel cells (PEMFCs) in heavy-duty vehicles and other demanding applications, such as aviation, would be simplified if the stacks could operate above 100 °C instead of the traditional low temperature (LT, up to 80 °C), thereby allowing a reduction in cooling system in size and power. This review offers a comprehensive compilation of experimental studies reported in the literature on PEMFCs operated in the intermediate temperature (IT)-range, here defined as above 80 °C and up to 120 °C, which represented the targeted upper temperature for PEMFCs. Membranes, electrodes and gas diffusion layers for IT-PEMFCs are discussed. Particular attention is paid to polymers in membranes and catalyst layer ionomers. Results from current state-of-the-art perfluorosulfonic acids and alternatives, including hydrocarbon polymers, are evaluated considering their properties and limitations. Further, system benefits and drawbacks of IT- compared to the traditional LT-operation are discussed, such as the interplay between vapour and oxygen pressure, hydrogen crossover and water management. We report on the lack of consistency between ex-situ and in-situ studies and underline the importance of in-situ tests, proposing guidelines to evaluate novel materials. For IT-operation, the development of stable polymers, which are the weakest components of the PEMFCs, is the most urgent challenge. As degradation happens faster at higher temperatures, further long-term tests are needed above 80 °C and accelerated stress tests should be specifically designed for IT-operation according to the polymer chemistries. We conclude that, compared to LT-, IT-operation requires improved materials and additional research.

Gas diffusion layers (GDLs), a critical component in (Formula presented.) / (Formula presented.) proton exchange membrane fuel cells (PEMFCs), are commonly treated with polytetrafluoroethylene (PTFE) for controlling hydrophobicity. However, the influence of the GDL's native microstructure on the final PTFE spatial distribution is still poorly understood. We compare the PTFE distribution in a dry-laid GDL containing a native binder with that in a wet-laid, binder-free GDL. To analyze the GDL microstructure, we perform scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and confocal Raman spectroscopy, with (Formula presented.) resolution at identical locations. We find that the binder acts as a scaffold for PTFE agglomerates to deposit, independent of the fiber locations. We show that PTFE deposited on the binder phase results in a significantly lower effect on the dry oxygen transport resistance, measured using a limiting current method at low oxygen concentration.