Designing High‐Elasticity Proton Exchange Membranes: Synergistic Effects of Hydroxyapatite Nanoparticles and Polyurethane Matrix in Perfluorosulfonic Acid‐Based Composites

ABSTRACT The inherent incompatibility of perfluorosulfonic acid (PFSA)—stemming from its rigid fluorinated backbone and elevated dipole moment—is overcome by the synergistic integration of hydroxyapatite (HA) nanoparticles into a polyurethane (PU)‐modified PFSA matrix, enabling unprecedented interfacial proton transport pathways. The optimized membrane with 4 wt% HA loading demonstrates remarkable improvements over the PFSA&PU membrane: a tensile strength of 11.89 MPa, an elongation at break of 224.46%, a proton conductivity of 0.235 S/cm at 80°C, and a H 2 /air fuel cell power density of 191 mW/cm 2 . After 100 h OCV hold, the PFSA&PU + 4wt%HA membrane retained an OCV of 0.757 V, with 4.5% less degradation than the baseline PFSA&PU membrane. Notably, the membrane exhibits exceptional elastic recovery, with only 14% residual strain after 150% stretching and a mere 7.65% reduction in mechanical strength after deformation. The test results indicate that this composite membrane has excellent potential for fuel cell applications.