【作者】 邓会宁；

【导师】 王宇新；

【作者基本信息】 天津大学 ， 化学工程， 2004， 博士

【摘要】 直接甲醇燃料电池（DMFC）以其高效、高能量密度、低排放和燃料储运及补充方便等特点被认为是适应未来能源和环境要求的理想动力源之一。目前,DMFC主要面临两大难题:一是通常使用的质子交换膜的阻醇性能较差;二是阳极催化剂对甲醇反应的催化活性较低。研制耐高温和高导电性的质子交换膜,使电池的工作温度提高,可以提高催化剂的催化活性,同时简化系统的热管理。因此,本论文在新型阻醇质子交换膜和耐高温的质子交换膜方面进行了新的尝试。含二氮杂萘酮结构聚醚酮（PPEK）、聚醚砜（PPES）和聚醚砜酮（PPESK）系列聚合物具有热稳定性高和机械强度好等优异特性。作为一种碳氢主链聚合物,该系列聚合物相对全氟磺酸聚合物而言价格低廉。以含杂萘联苯结构的系列聚合物为基材我们制得了一系列不同磺化度的磺化杂萘联苯聚醚酮（SPPEK）、磺化杂萘联苯聚醚砜（SPPES）和磺化杂萘联苯聚醚砜酮（SPPESK）膜,首次考察了这类膜用于DMFC的可行性。实验发现,磺化度为50%的SPPEK膜和磺化度为49%的SPPES膜在高温下的电导率在10-2S·cm-1,磺化度为131%的SPPESK膜在高温下的电导率接近Nafion膜。同时这三种膜的阻醇性能均优于Nafion膜。三种膜在不同温度下的电导率和甲醇透过系数的综合性能评价指标均高于Nafion115膜。杂多酸具有较高的电导率和良好的热稳定性,是一类高性能的质子导体。但是由于其易溶于水、无法成膜等缺点导致其不能作为固体电解质在燃料电池中使单独用。PPEK具有较高的热稳定性和良好的成膜性,但本身不具有质子导电性。因此我们考察了一系列PPEK为基体的杂多酸掺杂膜的性能。实验发现,在磷钨酸（PWA）和硅钨酸（SiWA）掺杂PPEK膜中,杂多酸团聚成颗粒分散在PPEK相中,膜的导电性较差。在PPEK中加入亲水性的聚乙烯基吡咯烷酮（PVP）共混,并进行杂多酸的掺杂,得到的复合膜的电导率比共混前显著提高。但PPEK与PVP间存在相分离,杂多酸主要存在于PVP相中。通过磺化对PPEK进行了亲水改性,PWA在SPPEK中的分散均匀。在以DS为58%的SPPEK为基膜的复合膜测试四天,PWA在水中的溶出不超过2%。PWA掺杂量为60%的SPPEK（DS=58%）膜在150℃下的电导率达到10-1 S·cm-1。而SiWA在SiWA/SPPEK膜中团聚成颗粒,在水中的溶出严重。因此将SiWA负载在SiO₂上,通过SiO₂的分散将SiWA均匀地分散到SPPEK膜中,SiWA在膜中的溶出显著下降。更多还原

【Abstract】 Direct methanol fuel cells (DMFC) have attracted considerable attentions as analternative to the present power sources, since they offer numerous benefits, includinghigh efficiency, high power density, low or zero emissions and easy fuel carriage.However, at present, two major technology problems in DMFC still restrict theirperformance and applications. One problem is methanol crossover from anode tocathode and the other is slow kinetics of methanol oxidation. If DMFC can beoperated at higher temperature, the activity of catalyst can be improved and heatmanagement simplified. This will require new membranes that are more heat-tolerantthan presently used Nafion membrane. In this study, development of methanol barrierconducting membranes with high thermal stability was attempted.Poly(phthalazinones) (PPs) including poly(phthazinone ether ketone) (PPEK),poly(phthalazinone ether sulfone) (PPES) and poly(phthalazinone ether solfoneketone) (PPESK) are polymers with high thermal stability and excellent mechanicalstrength. Moreover, those aromatic hydrocarbons are much cheaper compared withthe perfluorosulfonic acid (PFSA) polymer of present fuel cell membranes.SPPEK, SPPES and SPPESK membranes with various degree of sulfonation (DS)were prepared and the feasibility of applying these membranes in DMFC was studied.The proton conductivity of SPPEK (DS=50%), SPPES (DS=49%) membranes isabout 10-2S·cm-1 at temperatures above 100℃, and the conductivity of SPPESK(DS=131%) membrane is closed to that of Nafion membrane. Methanol permeabilityof the three membranes is lower than that of Nafion membrane. If the ratio ( σ /P) isused to characterize the performance of a membrane for DMFC, the ratio of thesethree membranes are better than Nafion115 membrane at the temperatures tested.Heteropoly acids (HPAs) are inorganic solid electrolytes with high protonconductivity and thermal stability. But HPAs cannot be made to a self-supportingmembrane. On the other hand, PPEK has good film-forming property and highthermal stability but cannot conduct proton. To combine the advantages of the two, aserial of HPAs doped PPEK membranes are prepared. The proton conductivity of thePWA/PPEK and SiWA/PPEK membrane is low due to poor dispersion of HPAs inPPEK. With the hydrophilic polymer of PVP added, the conductivity of the compositemembranes was improved. But phase separation of the two polymers was observedand the HPAs mainly disperse in PVP. PPEK becomes more hydrophilic whenmodified by sulfonation. A homogeneous membrane can be gotten with PWA dopedSPPEK. When immersed in water, less than 2% PWA was found lost in the PWAdoped SPPEK(DS=58%) membranes. But the dispersion of SiWA in SPPEKmembrane is poor and the lost of SiWA is much higher. So SiWA/SiO2 was derivedand SiWA was found well dispersed in the SiWA/SiO2 doped SPPEK membrane andthe lost of SiWA decrease when immersed in water.更多还原