燃料电池用新型磺化聚苯并咪唑交联膜的制备与性能

Preparation and Properties of Novel Cross-Linked Sulfonated Polybenzimidazole Membranes for Fuel Cell Applications

将四胺单体4,4′-二(3,4-二氨基苯氧基)联苯(BDAPB)与二酸单体4,4′-二苯醚二甲酸(DCDPE)及四胺单体3,3′-二氨基联苯胺(DAB)在伊顿试剂(Eaton’s reagent,甲磺酸与五氧化二磷的质量比为10∶1)中进行无规共聚,合成了一系列聚苯并咪唑共聚物PBI-x(x为BDAPB在四胺单体中的摩尔分数)。然后通过后磺化和共价交联剂双酚A型环氧处理制得了一系列磺化聚苯并咪唑交联膜S-PBI-x-Cy(y为环氧基与咪唑基的物质的量之比)。采用热重分析、拉伸测试、芬顿试验等,研究了质子交换膜的热稳定性、力学性能、吸水率、溶胀率、质子电导率、抗自由基氧化稳定性能及电池性能。结果表明:所制得的交联膜都显示出良好的力学性能,膜的质子电导率随着BDAPB摩尔分数的增加而显著增大;当BDAPB的摩尔分数达到30%时,其质子电导率高于全氟磺化聚合物膜Nafion 212的质子电导率。交联处理降低了膜的溶胀率,且交联密度越高,溶胀率降低越显著。由S-PBI-30-C15组装成的单电池(H2-O2体系)显示出优异的发电性能,其在90℃和70%相对湿度下的最大输出功率密度达到1.11 W/cm^2,高于相同条件下由Nafion212组装成的单电池的最大输出功率密度(0.95 W/cm^2)。

A tetraamine monomer,4,4′-bis(3,4-diaminophenoxy)biphenyl(BDAPB),was randomly copolymerized with two other monomers of dicarboxylic,4,4′-dicarboxyldiphenyl ether(DCDPE),and tetraamine,3,3′-diaminobenzidine(DAB)in Eaton′s reagent(the mass ratio of methanesulfonic acid to phosphorus pentoxide was 10∶1)yielding a series of polybenzimidazole copolymers(PBI-x,x referred to the molar fraction of BDAPB in the tetraamine monomers).The resulting PBI-x was further post-sulfonated and subsequently covalently cross-linked(cross-linker:bisphenol A epoxy resin)to give a series of covalently cross-linked sulfonated polybenzimidazole copolymer membranes(S-PBI-x-Cy,here,y referred to the molar ratio of epoxy groups to benzimidazole groups).The thermal stability,mechanical properties,water uptake,swelling ratio,proton conductivity,radical stability and single cell performance of the exchange proton membranes were investigated.The prepared cross-linked membranes exhibited good mechanical properties.With an increase in molar fraction of BDAPB moiety,the proton conductivities of the membranes was increased remarkably.As the molar fraction of BDAPB reached 30%,its proton conductivity was higher than that of Nafion 212.The covalent cross-linking treatment led to reduction in membrane swelling ratio,and the higher cross-linking density,the more significant reduction in swelling ratio.The single cell assembled with the S-PBI-30-C15 exhibited excellent performance(H2-O2),and its maximum output power density reached 1.11 W/cm^2 at 90°C and 70%relative humidity,which was higher than that of Nafion 212(0.95 W/cm^2)under the same conditions.