【作者】 何瑶；

【导师】 吕长利；

【作者基本信息】 东北师范大学 ， 高分子化学与物理， 2014， 博士

【摘要】 质子交换膜(PEM)作为质子交换膜燃料电池(PEMFC)的核心部件在很大程度上决定了PEMFC性能的好坏。现在广泛应用于PEMFC的PEM是杜邦公司生产的Nafion膜。虽然Nafion膜具有高质子传导、化学稳定性好等优点，但它的质子传导强烈依赖膜内的水含量，高温时膜性能急剧下降，在作为直接甲醇燃料电池(DMFC)的PEM时燃料渗透严重，并且Nafion的生产过程复杂，造价昂贵。这些问题都是影响Nafion广泛应用的重要原因。磺化的芳香族聚电解质由于具有良好的机械性能，化学稳定性和热稳定性，尤其是低于Nafion的甲醇渗透和生产成本，使其在近年的PEM研究中备受科研和能源开发机构的青睐。我们知道，在PEM中质子的传导主要是在膜的亲水区域内，亲水区的连续性越好越有利于质子传导。在磺化的无规共聚物膜中，磺酸基会聚集形成大的离子簇，亲水区之间的相对间距很大，因此质子不能在这种结构中快速的传导。为了获得综合性能好，并且具有连续质子传输通道的PEM，很多方法被用于制备改性PEM。在本论文中，我们以磺化芳香聚电解质作为基体，用不同的方法构筑了一系列综合性能好，具有连续离子簇网络和长程质子传输通道的复合质子交换膜材料。具体工作分为四个部分：在第一部分工作中，我们利用原位聚合的方法将具有大量酰胺键的聚异丙基丙烯酰胺(PNIPAm)引入到无规共聚合SPI基体中，制备了一系列具有不同PNIPAm含量的SPI-cPNIPAm半互穿网络PEM。PNIPAm中的酰胺键与SPI中的磺酸基之间形成的氢键相作用以及半互穿的三维网络结构能够调节复合膜的微观结构和性能。当磺酸基和酰胺键摩尔比为1:1时，SPI-20%-cPNIPAm膜样品中离子簇尺寸最小，分布均匀且连续，形成了利于质子传导的通道。25oC时，该样品膜的质子传导是纯SPI膜的2倍，电池能量密度由纯膜的44mW cm2提高到72mW cm2。同时复合膜也具有良好的机械性能和热稳定性。在第二部分工作中，我们从不同尺寸石墨出发，制备了三种具有不同尺寸的氧化石墨烯(GO)。将不同尺寸的GO与SPI复合，用于考察GO的尺寸效应对SPI/GO复合膜微观结构和性能的影响。研究发现，在相同的含量下，尺寸最小的GO对SPI基体的微观结构和性能影响最大。在最小GO掺杂为0.5wt%的PEM中离子簇从纯SPI膜中的25nm缩小到6nm，分布均匀且连续，形成了有利于质子传导的微观结构。同时25oC下，这个样品膜的质子传导高于纯SPI膜4倍。复合膜的机械性能、抗氧化稳定性、尺寸稳定性和阻醇性能也都有不同程度上的提高。实验结果说明，GO的引入能够调节PEM的微观结构，优化PEM的综合性能。在第三部分工作中，我们通过8-羟基喹啉-5-磺酸盐中的羟基与3-异氰酸酯基丙基三乙氧基硅烷中的异氰酸酯的反应，得到了含有氮杂环和磺酸基的有机硅氧烷偶联剂(SiSQ)。在表面活性剂(模板剂)的存在下，采用溶胶-凝胶的方法将SiSQ引入到SPI基体中，得到了一系列含有不同介孔有硅氧烷(MsiSQ)掺杂量的SPI-MSiSQ复合膜。研究发现MSiSQ相与SPI基体之间有更好的相容性，磺酸基的引入减少了掺杂组分对SPI膜中磺酸基浓度的稀释作用。复合膜的质子传导和阻醇性随着MSiSQ含量的增加而增加。当MSiSQ含量为40wt%时，在25oC下，复合膜的质子传导为0.23S cm-1，甲醇渗为1.8×10-8cm2/S，选择性为12.8×106Sscm-3，这与纯膜相比分别提高了3、6、23倍。这主要归因于：一方面是MSiSQ中的喹啉氮原子与SPI中的磺酸基之间的相互作用促使SPI中的大尺寸离子簇分散成尺寸更小的离子簇，在膜中形成了均一连续的质子传输通道；另一方面则是磺化有机硅氧烷中的磺酸基与表面活性剂作用，去除表面活性剂后磺酸基聚集在介孔内，为质子的传导提供了长程的质子传导通道。此外，复合膜的电池性能、机械性能、热稳定性和抗氧化性都有很大程度的提高，有望用于DMFC。在第四部分工作中，我们以聚酯纤维为基底，利用GO与SPES之间的氢键相互作用，使两者通过层层组装的方式在聚酯纤维的表面形成GO与SPES组装的多层结构，每一层中磺酸基都沿纤维轴向排列，这为质子的传导提供了长程的质子传导通道，促进质子的快速传导。将SPES与多层组装聚酯纤维复合，并对复合膜的结构和性质进行了表征。结果表明：随着组装层的增加复合膜中的质子传导率逐渐升高。同时复合膜的机械性能和阻醇性也比纯SPES膜有明显的提高。实验证明层层结构修饰的纤维能构筑更多长程质子传输通道。更多还原

【Abstract】 Proton exchange membrane (PEM), a core component of Proton exchangemembrane fuel cell (PEMFC), determines the performances of PEMFC to a greatextent. Today, Nafion membrane produced by DuPont is still widely used in PMFC asPEM. Although the Nafion membrane has high proton conductivity, good chemicalstability and other advantages, it also has many disadvantages, such as protonconductivity strongly depends on the water content in membrane, high fuelpenetrability, performances rapidly decline in high temperature, complex productionprocess, high cost etc. These problems are important reasons for limiting the wideapplication of Nafion. Sulfonated aromatic polymer electrolytes are promisingmaterial for PEM due to its good mechanical properties, chemical and thermalstability. Especially, the low methanol permeability and production cost comparedwith Nafion. Therefore sulfonated aromatic polymer electrolytes are widelyconcerned by scientific and energy institutions. As we know, the proton conduction ismainly occurred in the hydrophilic region of PEM, continuous hydrophilic region isadvantageous to the proton conduction. In the sulfonated random copolymermembrane, sulfonic acid groups will aggregate to large clusters and form hydrophilicregions, and the distance between the hydrophilic regions is correspondingly big, sothe proton can not fast conducting in this structure. In order to obtain PEMs withexcellent comprehensive performances and continuous proton transmission channel,many methods have been used for modifying PEM.In this paper, base on sulfonated aromatic polymer electrolyte, we have constructeda serie of PEM with outstanding comprehensive performances, continuous ioniccluster network or long-range proton transmission channel by different approaches.The specific work is divided into four parts:In the first part, we introduced the poly N-isopropylacrylamide (PNIPAm) with alot of amido bonds into SPI via in situ polymerization reaction, and prepared a seriesof semi-interpenetrating polymer networks (semi-IPNs) with different content ofPNIPAm. The hydrogen bond interaction between sulfonic acid groups of SPI andamido bonds of cPNIPAm and the semi-IPNs structure could regulate themicrostructure and properties of composite membranes. When the molar ratio ofsulfonic acid groups and amido bonds is1:1, the SPI-20%-cPNIPAm membrane hassmall size ionic clusters (>6nm) with uniform and continuous distribution which isbeneficial to the proton conduction. At25oC, the proton conductivity ofSPI-20%-cPNIPAm membrane is one time higher than that of the pure SPI membrane, the power density is improved from44mW cm2of SPI to72mW cm2. The resultsshow that the proton transmission channels beneficial to the proton are formed. At thesame time, the semi-IPNs PEMs also have good mechanical properties and thermalstability.In the second part, we synthesized three kinds of GO with different sizes fromvarious sizes of graphite. Different sizes of GO were incorporated into SPI toinvestigate the size effect on the microstructure and performance of SPI/GOcomposite membranes. The study found that in the three kinds of GO, the small sizeGO has the biggest influence on the microstructure and performance of compositePEM at the same content. In the composite PEM with0.5wt%small GO, the ionicclusters are shrinked from25nm of SPI to6nm and dispersed uniformly, resulting inan advantageous microstructure for proton conduction. At25oC, the protonconductivity of this composite PEM is four times higher than that of pure SPI. Themechanical properties, oxidative stability, dimensional stability and methanol--resistance of composite membranes are also improved. This experimental resultsshow that the incorporation of GO can control the microstructure and optimize theperformances of composite PEM.In the third part, we synthesized a kind of organic silane coupling agent（SiSQ）with sulfonic group and N-heterocycle through the reaction between8-hydroxyquinoline-5-sulfonate and3-isocyanatepropyltriethoxysilane. In thepresence of surfactant (template), SiSQ was introduced into SPI matrix using sol-gelmethod, and obtained a series of SPI-MSiSQ composite membranes with differentMSiSQ content. The study found that a better compatibility is formed betweenMSiSQ phase and SPI matrix. The introduction of sulfonic group has diminished thedilution effect of the inorganic component to the concentration of sulfonic acid groupin SPI. The proton conductivities and methanol-resistances of composite membranesare increased with the increasing of MSiSQ content. At25oC, the composite PEMwith40wt%MSiSQ has the best result, high proton conductivity (0.23S cm-1), lowmethanol permeability (1.8×10-8cm2S-1), optimal selectivity (12.8×106Ss cm-3),which is3,6and23times higher than that of pure SPI respectively. The excellentperformances of the composite membranes can be summed up in two points: One isthe interaction between the nitrogen atoms of quinoline in MSiSQ and sulfonic acidgroups in SPI reduced the large size ionic clusters in SPI into smaller one, andforming a uniform and continuous proton transmission channel. Another is theinteraction between sulfonic acid groups of sulfonated organic siloxane and surfactant.When removing the surfactant, the sulfonic acid groups will gather within themesopores, which also provides a long-range proton transmission channel to proton.Cell performance of composite membranes and other properties are all improvedlargely, which is expected to be used in DMFC. In the fourth part, base on the polyester fibers, using the hydrogen-bondinginteraction between GO and sulfonated polyethersulfone (SPES), we layer-by-layerassembled GO and SPES on the surface of polyester fibers, then multilayer structureis formed on the surface of polyester fiber. In each layer, sulfonic acid groups arearranged along the axis of fiber, which provide long-range proton transmissionchannels, promoting rapidly proton conduction. The performances of compositemembranes base on SPES and multilayer assembled polyester fiber were tested. Theexperimental results show that, the proton conductivity of composite membrane isincreased by increasing the assembly layers. At the same time, the mechanicalproperties and methanol-resistances of the composite membranes are obviouslyincreased.更多还原