Preparation And Properties Of Side Chain Proton Exchange Membrane For Fuel Cells Applications

Proton exchange membrane is the key component of proton exchange membrane fuel cell, and play a direct and decisive role in the performance of fuel cell, but its high cost, and produce CO poisoning easily at low temperature work, the water will loss in the membrane and lead to lower proton conductivity at the high-temperature work, these obvious shortage limits the development and application of membrane.Due to its good mechanical properties, high thermal stability, chemical stability and low cost, aromatic sulfonated polymers have been employed widely as PEM materials. In this paper, we change the past design ideas of sulfonic acid groups introduced into the polymer main chain, synthesized the side-chain-style aromatic sulfonated polymers S-SPAEEK.to test the sulfonated polymer by infrared, and test the performance of side-chain proton exchange membrane. The infrared spectra showed that the sulfonic acid groups have been grafted onto the side chain of the polymer. The Td5%loss weight temperature of S-SPAEEK at above200℃, show the good thermal stability. S-SPAEEK has higher water absorption and proton conductivity, The proton conductivity is0.073S/cm of S-SPAEEK with0.8degree of sulfonation at80℃, the methanol permeability is8.9×10-7cm2/s, show the good potential for the usage in high temperature PEMFC.In order to enhance the proton conductivity of S-SPAEEK, the polyvinyl alcohol (PVA) introduced and prepared the S-SPAEEK/PVA composite membrane, and research the performance of the composite membrane. The thermal stability has been improved by introduction of the PVA, and increased with increasing PVA content. The-OH of PVA has a strong water absorption, Improved the water absorption, water-retention capacity and proton conductivity of the composite membranes at high temperatures.S-SPAEEK/PVA cross-linking composite membrane prepared by heating method at high temperature, and infrared characterization the composite membrane of cross-linked structure, compared with non-cross-linked composite membranes showed that the composite membrane has formed a cross-linked structure. The thermal stability of the S-SPAEEK/PVA cross-linked composite membrane is higher than the non-cross-linked composite membrane, but water absorption, swelling ratio, proton conductivity and methanol permeability is reduced with the degree of cross-linking increased, However, the PVA content of15%,20%cross-linked composite membranes have enough water absorption and high proton conductivity at80℃.We synthetic the SPVA with concentrated sulfuric acid by passed sulfonation, composited with S-SPAEEK form S-SPAEEK/SPVA composite membrane.In the infrared Characterization spectra of the SPVA, the O=S=O asymmetric stretching vibration absorption peak indicate that-SO4H has been grafted onto the PVA main chain at1237cm-1.Water absorption and proton conductivity of composite membranes increased as SPVA content increases.