A Maximization of the Proton Conductivity of Sulfonated Poly(Ether Ether Ketone) with Grafted Segments Containing Multiple, Flexible Propanesulfonic Acid Groups

Construction of Successive Proton Conduction Channels to Accelerate the Proton Conduction Process in Flexible Proton Exchange Membranes

Successive proton conduction channels are constructed with the spin coating method in flexible proton exchange membranes (PEMs). In this research, phosphoric acid (PA) molecules are immobilized in the multilayered microstructure of Kevlar nanofibers and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) polymer molecular chains. As a result, successive proton conduction channels can accelerate the proton conduction process in the prepared membrane with the multilayered microstructure. Additionally, the microstructure fractures of the composite membranes from the external force of folding and stretching operations are modified by the inner PA molecules. Notably, numerous PA molecules are further combined through formed intermolecular hydrogen bonding. The stretched membrane absorbs more PA molecules owing to the arrangement of PA molecules, Kevlar nanofibers, and SEBS molecular chains. The stretched membrane thus exhibits the enhanced proton conduction ability, such as the through-plane proton conductivity of 1.81 × 10-1 S cm-1 at 160 °C and that of 4.53 × 10-2 S cm-1 at 120 °C lasting for 600 h. Furthermore, the tensile stress of PA-doped stretched membranes reaches (3.91 ± 0.40)-(6.15 ± 0.43) MPa. A single proton exchange membrane fuel cell exhibits a peak power density of 483.3 mW cm-2 at 120 °C.