Synthesis and characterization of hybrid membranes based on sulfonated poly(ether ether ketone) (SPEEK) and polysiloxane

Abstract

Polymer electrolyte membrane fuel cells (PEMFC) for hydrogen and methanol have attracted the attention of research groups for many years mainly because they are promising candidates for clean and renewable power sources. The most common commercial product used as PEM is Nafion®. However, certain limitations and high production costs stimulate the research of new materials. In this work, new hybrid proton-conducting membranes for PEMFC based on sulfonated poly(ether ether ketone) and an inorganic–organic polysiloxane phase were obtained with the objective of improving its mechanical, thermal, and chemical resistance properties. The hybrid membranes were prepared by dissolving the base polymer in DMSO and adding different amounts of the polysiloxane phase previously obtained from polydimethylsiloxane and a cross-linking agent (tetraethyl orthosilicate or phenyltrimetoxysilane). Membranes were characterized using infrared spectroscopy and thermal analysis. Macroscopic properties as water uptake, ion-exchange capacity, and proton conductivity were determined. The methanol permeabilities were in the range of 5.53 × 10−7− 8.36 × 10−7 cm2/s, which is several times lower than that of Nafion® 117 (1.55 × 10−6 cm2/s). The hybrid membranes with both cross-linkers also exhibited higher proton conductivity with respect to Nafion® 117 (40 mS/cm) at 80°C and 90% relative humidity.