Acid–base hybrid polymer electrolyte membranes based on SPEEK

A new series of proton-conducting membranes has been developed that consists of sulfonated poly(ether ether ketone) (SPEEK) and 3-aminopropyltriethoxy silane (APTES) prepared over a wide range of compositions. The APTES was added to SPEEK to address its deficiencies, such as high dimensional swelling and water uptake in SPEEK membranes at elevated temperatures. A dispersed phase of amino silica was formed through hydrolysis and condensation of APTES. The silica contributes to the suppression of permeation of reactants across the membrane and the electrostatic interaction between the basic amine groups of APTES and the acidic sulfonic groups of SPEEK suppresses loss of silica from the membrane. The hybrid SPEEK and APTES membranes are stable up to about 80 °C and demonstrate a higher ratio of proton conductivity to methanol permeability than that of Nafion® 117.