Proton-Exchange Sulfonated Poly （ether ether ketone） （SPEEK）/SiOx-S Composite Membranes in Direct Methanol Fuel Cells

• Published in: Chinese journal of chemical engineering no. 2; pp. 207 - 213
• Main Author: 高启君 王宇新 许莉 卫国强 王志涛
• Format: Journal Article
• Language: English
• Published: 2009
• Subjects: SiOx; 复合膜; 甲醇渗透率; 直接甲醇燃料电池; 磺化聚醚醚酮; 质子交换; 质子导电性
• ISSN: 1004-9541; 2210-321X

A sulfonated poly（ether ether ketone） （SPEEK） membrane with a fairly high degree of sulfonation （DS） can swell excessively and even dissolve at high temperature. To solve these problems, insolvable functionalized silica powder with sulfonic acid groups （SiOx-S） was added into the SPEEK matrix （DS = 55.1%） to prepare SPEEK/ SiOx-S composite membranes. The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder. Pure SPEEK membrane swelled 52.6% at 80℃, whereas the SPEEK/SiOx-S （15%, by mass） membrane swelled only 27.3% at the same temperature. From room temperature to 80℃, all SPEEK/SPEEK/SiOx-S composite membranes had methanol permeability of about one order of magnitude lower than that ofNafion115. Compared with pure SPEEK membranes, the addition of the SiOx-S powder not only leads to higher proton conductivity, but also increases the dimensional stability at higher temperatures, and greater proton conductivity can be achieved at higher temperature. The SPEEK/SiO4-S （20%, by mass） membrane could withstand temperature up to 145℃, at which in 100% relative humidity （RH） its proton conductivity exceeded slightly that of Nafion 1 15 membrane and reached 0.17 S·cm^-1, while pure SPEEK membrane dissolved at 90℃. The SPEEK/SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.