Feasibility Validation and Impact Analysis of Mass Fraction for PDMS-Based Fluorine-Free Microporous Layers

Commercial fluorinated microporous layers (MPLs) for proton exchange membrane fuel cells (PEMFCs) face regulatory challenges due to perfluorooctanoic acid (PFOA) emissions. This study proposes a fluorine-free hydrophobic strategy using polydimethylsiloxane (PDMS), prepared via a binary solvent method to replace polytetrafluoroethylene (PTFE). Electrochemical performance and microstructure are systematically benchmarked against commercial 20 wt% PTFE-MPL. Results indicate that PDMS forms a uniform, isotropic interconnected porous network, avoiding the directional cracks observed in PTFE-MPLs. At equivalent loading (20 wt%), PDMS-MPL reduces mass transport resistance by 28% at 2.0 A cm −2 . Further optimization within a 5–30 wt% range identifies 5 wt% PDMS as the optimal formulation, effectively balancing interface hydrophobicity and pore accessibility. This formulation achieves a peak power density of 1.102 W cm −2 , demonstrating that the PDMS-MPL can achieve performance comparable to or competitive with established PTFE systems, while providing clear environmental and energy-saving benefits. Electrochemical impedance spectroscopy (EIS) confirms that the performance enhancement stems from synergistic reductions in ohmic and mass transport resistances. The proposed PDMS-based MPL offers a high-performance, eco-friendly alternative with lower processing energy requirements.