High methanol resistant polyelectrolyte membrane based on semi-crystalline Poly(ether ketone) with densely sulfonated side chain for direct methanol fuel cell

Different from the widely developed amorphous polyelectrolyte membrane materials, semi-crystalline sulfonated poly(ether ketone) (PEK-SPx) membranes composed of crystalline poly(ether ketone) main chain and densely sulfonated side chain are prepared. Wide-angle X-ray diffraction analysis indicates that these membranes manifest crystalline nature. The dimensional stability and methanol resistance of PEK-SPx membranes are greatly enhanced by introduction of semi-crystalline structure. The dimensional change in pure methanol at 60 °C and methanol permeability of PEK-SP20 membrane is only 25.9% and 36 × 10−8 cm2 s−1, respectively. In addition, coupled with excellent thermal stability, oxidative stability, good mechanical property, satisfactory proton conductivity and distinct micro-phase separation, PEK-SP20 membrane exhibits considerable single cell performance. Overall, semi-crystalline PEK-SPx membranes are a promising new type of proton exchange membranes for application in direct methanol fuel cells.