Multilayer Membranes Based on Sulfonated Poly(Ether Ether Ketone) and Poly(Vinyl Alcohol) for Direct Methanol Membrane Fuel Cells

Much work has been conducted on the substitutes for Nafion as proton exchange membrane materials. Some researches are focused on the heterogeneous multilayered membranes reported by R. Jiang [J. Electrochem. Soc. 153 (2006) A1554], B. Yang [Electrochem. Commun. 6 (2004) 231] and S. Ren [J. Membr. Sci. 247 (2005) 59]. However, just as the dependence of methanol crossover upon the layer with the lowest permeability, the proton transfer ability is major confined by the layer with the poorest conductivity. Moreover, various swelling ratio and contractibility of sub-layers will make the hidden problems of separation between catalyst layer and proton exchange membrane become more obvious. We present here a multilayered membranes containing five thin layers of sulfonated poly(ether ether ketone)(SPEEK) and five thin layers of poly(vinyl alcohol)(PVA). SPEEK layers and PVA layers were located alternatively in the composite membrane. The swelling behaviors of PVA layer are restrained by both sideward SPEEK layers. Methanol crossover is efficiently alleviated piece by piece without visible proton conductivity loss. The preliminary investigation in DMFC suggests its promising application as resisting methanol and proton exchange membrane.