SPES/PWA/SiO_2复合质子交换膜的性能

以磺化聚醚砜(SPES)为基体,以不同比例的SiO2溶胶与磷钨酸(PWA)为掺杂物,制备了一种有望用于直接甲醇燃料电池(DMFC)的新型SPES/PWA/SiO2有机-无机复合膜,并经热失重分析(TGA)、差示扫描量热仪(DSC)、扫描电镜(SEM)-X射线能谱分析(EDX)等对膜的结构和性能进行了表征,探讨了复合膜用作质子交换膜的可能性.结果表明:复合膜较纯SPES膜具有更高的热稳定性、玻璃化转变温度和吸水率;虽然在室温和电池操作温度(80℃)下,复合膜的拉伸强度均低于纯SPES膜,但即使当SiO2含量高达20%(w)时,复合膜的拉伸强度仍高于Nafion112膜的;SEM图片显示SiO2和PWA在膜中分布均匀,这将有利于连续质子传输通道的形成.对于SiO2含量为15%(w),PWA含量为6%(w)的复合膜,其室温质子传导率达到了0.034S·cm-1,与Nafion112膜的相当,但其甲醇渗透率明显降低,仅为商用Nafion112膜的七分之一左右,这表明该复合膜在直接甲醇燃料电池中具有良好的应用前景.

Properties of SPES/PWA/SiO2 Composite Proton Exchange Membranes

Novel sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica organic-inorganic composite membranes for application in direct methanol fuel cells (DMFCs) were prepared by doping SiO₂ sol and PWA into SPES matrix. The structure and performance of the obtained membranes were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), etc. Compared with the pure SPES membrane, SiO₂ and PWA doping led to higher thermal stabilities, a higher glass transition temperature (T_g), and higher water uptake. At 20℃ and a fuel cell operating temperature of 80℃, the tensile strength of all the composite membranes was lower than that of the SPES membrane. However, even when the content of SiO₂ was as high as 20% (w), the composite membrane still possessed a higher strength than a Nafion 112 membrane. The morphology of the composite membranes indicated that SiO₂ and PWA were uniformly distributed throughout the SPES matrix, which may facilitate proton transport. The proton conductivity of the composite membrane (SPES-P-S 15%: 15% (w) SiO₂ and 6% (w) PWA) reached 0.034 S·cm^-1, which was similar to that of the Nafion 112 membrane at room temperature. However, methanol permeation through the SPES-P-S 15% composite membrane decreased dramatically and was only one-seventh that of the Nafion 112 membrane. This excellent selectivity of the SPES/PWA/SiO₂ composite membrane points to its potential use as a promising electrolyte for DMFCs.