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

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. Highlights HA induces porous PFSA + PU, boosting PEM elasticity and conductivity. Adding HA increases elongation by 156.73% and conductivity by 45.96%. PFSA&PU + HA membrane achieves 191 mW/cm 2 power density under H 2 /air conditions.