Preparation And Characterization Of QAPPESK-OH And Its Modified Membranes

Alkaline anion exchange membrane fuel cell (AAEMFC) has many advantages, such as improving oxidation rate of anode, reducing permeation of feed fluid, especially methanol, extending catalysts range, simplifying water management and etc, therefore the research of AAEMFC becomes new hotspot. Alkaline anion exchange membrane (AAEM) is the core component of AAEMFC, its properties directly affect the performance of AAEMFC. However, the researches aim at AAEMFC begin too late, recent commercial AAEM can not maintain high ionic conductivity and stability, which make it can not meet the demand of AAEMFC, upon that, many researchers have focused their study on developing better performing AAEM, which can be used in AAEMFC.In this paper, high performance AAEM is expected to be developed. Chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) was the basic material for the preparation of new AAEM, it was synthesized from poly(phthalazinone ether sulfone ketone) (PPESK) using chloromethyl octyl ethers (CMOE) as chloromethylated regent. Afterward, alkaline quaternized poly(phthalazinone ether sulfone ketone) (QAPPESK-OH) was prepared through quternization and basification of CMPPESK, and then different effect factors of degree of quternization, which were confirmed by ion exchange capacity (IEC) were investigated, the optimized quaternization time was 12h and quaternization temperature was 40℃, the concentration of NaOH for basification was O.Olmol/L. The water uptake of QAPPESK-OH membrane increased from 18.9% to 34.6% when the IEC changed from 0.66mmol/g to 1.05mmol/g, at 30℃. At 33℃, the ionic conductivity of QAPPESK-OH membrane with IEC 1.0mmol/g was 2.2×10-2S/cm.In order to increase water uptake and then improve the ionic conductivity of QAPPESK-OH membrane, polyvinyl alcohol (PVA), which had good water absorption, was brought into AAEM, and then QAPPESK-OH/PVA blend membranes were prepared. The effects of PVA content on membrane preparation, water uptake, swelling degree, IEC, thermal stability, ionic conductivity and mechanical strength were all investigated. The results showed that smooth QAPPESK-OH/PVA blend membranes could be prepared when PVA content under 10wt%, thereinto blend membrane with 6wt% PVA displayed better performance, its water uptake reached 53.9% at 30℃, increased 94.6% than QAPPESK-OH membrane (IEC 0.97mmol/g, water uptake 27.7%). The ionic conductivity of QAPPESK-OH/PVA (6wt%) blend membrane was 2.43×10-2S/cm, higher than that of QAPPESK-OH membrane at 30℃.The swelling degree of blend membranes maintained around 15%, which had little change with temperature increasing. Besides, The thermal stability, mechanical strength and oxidation stability were also good enough for demand of AAEMFC.In order to further restrict membrane swelling, QAPPESK-OH/PVA crosslinked membranes which were crosslinked by glutaraldehyde were prepared. Although the swelling degree of QAPPESK-OH/PVA crosslinked membranes decreased a little, their mechanical strength and ionic conductivity were not as good as QAPPESK-OH/PVA blend membranes, which may be caused by heterogeneous reaction between solid membranes and liquid crosslinking solution, farther study should be made to improve the performance of QAPPESK-OH/PVA crosslinked membranes.