Proton-conducting composite membranes derived from sulfonated hydrocarbon and inorganic materials

Composite polymer membranes are prepared by embedding layered silicates such as Laponite and Montmorillonite (MMT) into sulfonated poly(ether ehter ketone) (sPEEK) membranes for fuel-cell applications. Sulfonation of the polymer increased membrane hydrophilicity to give good proton conductivity. Layered silicates incorporated into polymer membranes help to reduce swelling significantly in hot water; they also help to decrease methanol permeability. These polymer/clay composite membranes show thermal stability to 240 °C and (3–3.5)×10−3 S cm−1 proton conductivity at room temperature. In addition, methanol cross-over is reduced without a serious reduction in the proton conductivity. In a single-cell test using hydrogen and oxygen, the prepared membranes give current densities that are between 70 and 80% of those with Nafion 115 membranes. As a result, for polymer electrolytes, sPEEK/clay composite membranes offer a low-cost alternative to perfluorinated membranes.