超支化高选择性质子交换膜中多级自组装质子传输通道原位构建及优化研究

发布时间：2018-11-08 19:42

【摘要】：质子交换膜广泛应用于电化学能量转化装置,包括质子交换膜燃料电池(含直接甲醇燃料电池)、SPE水电解及钒氧液流电池中。由于具有良好的质子传导性、强的机械性能、抗氧化性和热稳定性,Nafion膜成为目前应用最广泛的质子交换膜。但是,Nafion膜存在选择透过性差的问题影响了其在直接甲醇燃料电池和钒氧液流电池中的大规模应用。Nafion膜选择透过性差在直接甲醇燃料电池应用中将导致严重的甲醇燃料渗透。直接甲醇燃料电池在工作过程中,由于Nafion膜的阻醇性能不好,甲醇分子很容易从阳极穿透膜到达阴极,不仅造成甲醇燃料的浪费,同时严重抑制了阴极的氧还原反应,从而导致电池工作电压和电池效率下降。因此,可以说高选择性质子交换膜的缺乏是影响直接甲醇燃料电池发展的绊脚石。而开发选择性好,价格低廉的新型质子交换膜是直接甲醇燃料电池发展的关键。同样,Nafion膜的选择性也影响了钒氧液流电池的发展进程。虽然Nafion膜极好的化学稳定性使其成为当前钒氧液流电池应用中主流膜。然而,Nafion膜存在的高的钒离子渗透性使得由Nafion膜组装的钒氧液流电池的电压效率、库仑效率和能量效率都较低。总的来说,设计和开发高选择性质子交换膜是当前直接甲醇燃料电池和钒氧液流电池领域的主要研究课题。高度有序的质子传输通道是保证质子高效传导,提高质子交换膜选择性的重要前提。所以,构筑高选择性质子传输通道是质子交换膜方向的最重要的研究课题。本论文通过调节质子传输功能聚合物微观结构实现质子传输通道在质子交换膜中的自组装,并通过优化质子交换膜中多级质子传输通道微观结构来实现质子交换膜选择性的进一步提升。具体研究内容如下所述:1、研究证实超支化聚酰胺质子交换膜可以有效地降低燃料渗透,同时提高质子传导性。此质子交换膜表现出比Nafion117高出至少15倍的阻醇性。在此基础上,本论文首次提出了一个新的概念——多级质子传输通道(HPCCs)。在这些HPCCs中,超支化聚酰胺分子内部高密度磺酸基团组成的质子传输通道称为一级质子传输通道(FOPCC)。另外,超支化聚酰胺分子封端功能基团与活化水分子间形成丰富的氢键网络被称为二级质子传输通道(SOPCC)。由于一级与二级质子传输通道之间的协同作用,超支化聚酰胺质子交换膜表现出高效的质子传输性能(0.282S/cm,80 oC)。通过调节合成超支化聚酰胺分子单体的纳米结构,实现对多级质子传输通道的优化,从而降低了质子交换膜的甲醇渗透性,同时其选择性提高了1倍多。2、在多级质子传输通道概念的基础上,本论文通过调节一级质子传输通道微观结构来进一步增强膜的阻醇性。首先合成了两种磺酸根密度不同的都以-COOH封端的聚酰胺大分子,通过将不同质量比例的两种聚合物用溶液浇铸法制备了一系列共混膜。由于两种聚酰胺大分子中的磺酸基团-SO3H密度不同,所以通过调节共混膜中两种分子比例可以实现质子交换膜中一级质子传输通道的调节,从而实现质子交换膜阻醇及选择性能的优化。3、使用类似想法,论文对多级质子传输通道中的二级质子传输通道的微观结构进行调节优化,通过温和的方法改变二级质子传输通道的氢键强度及保水性,以此来优化质子交换膜的整体性能。首先,设计并合成了以不同功能基团(-COOH和-NH2)封端,大小相似的超支化聚酰胺大分子;将这两种聚合物大分子按照不同的比例制备成复合膜。通过调整两种聚酰胺大分子的比例来调节共混膜中的二级质子传输通道的微观结构,质子交换膜的选择性比Nafion117高出1.7倍。4、基于前期设计合成的高选择性超支化聚酰胺质子交换膜,将其应用领域从直接甲醇燃料电池拓展至同样对选择性要求极高的钒氧液流电池中。超支化聚酰胺中多级质子传输通道形成的致密结构有效阻止了钒离子穿透。与Nafion117膜相比,超支化聚酰胺质子交换膜表现出良好的的质子/钒离子选择性,高达14.4×104S.s/cm3,比Nafion117膜高出3倍。5、由于聚酰亚胺良好的化学稳定性,设计并合成了超支化聚酰亚胺用于高选择性多级质子传输通道的构筑。聚酰亚胺质子交换膜机械性能比聚酰胺高出25%。透过该共混膜的甲醇渗透性很低以至于无法用仪器检测到。综上所述,通过大分子微观结构设计来构筑高效多级自组装质子传输通道,以此获得高选择性的质子交换膜,同时这些质子交换膜表现出良好的机械性能。本论文为应用于直接甲醇燃料电池及钒氧液流电池的新型质子交换膜的开发研究提供了一定参考。
[Abstract]:The proton exchange membrane is widely used in electrochemical energy conversion devices, including proton exchange membrane fuel cells (including direct methanol fuel cells), SPE water electrolysis and oxygen-enriched liquid flow cells. The Nafion membrane is the most widely used proton exchange membrane due to its good proton conductivity, strong mechanical properties, oxidation resistance and thermal stability. However, the problem of selective permeability of the Nafion membrane has an influence on the large-scale application of the Nafion membrane in the direct methanol fuel cell and the oxygen-enriched liquid flow cell. the poor selectivity of the nafion membrane will result in severe methanol fuel penetration in the direct methanol fuel cell application. in the process of operation, the methanol molecule can easily penetrate the membrane to the cathode from the anode through the membrane due to the bad alcohol resistance of the Nafion membrane, not only the waste of the methanol fuel is caused, but also the oxygen reduction reaction of the cathode is seriously inhibited, resulting in a decrease in the operating voltage of the battery and the efficiency of the battery. Therefore, it can be said that the lack of a high-selectivity proton exchange membrane is a stumbling block to the development of direct methanol fuel cells. The new type of proton exchange membrane with good selectivity and low price is the key to the development of direct methanol fuel cell. Similarly, the selectivity of the Nafion membrane also affects the development process of the oxygen-enriched liquid flow cell. Although the Nafion membrane has excellent chemical stability, it becomes the main membrane in the application of the present oxygen-enriched liquid-flow battery. However, the high ionic permeability of the Nafion membrane is such that the voltage efficiency, coulombic efficiency and energy efficiency of the oxygen-oxygen flow cell assembled by the Nafion membrane are low. In general, the design and development of a highly selective proton exchange membrane is a major subject in the field of direct methanol fuel cells and oxygen-enriched liquid-flow cells. The highly ordered proton transfer channel is an important prerequisite for ensuring the efficient conduction of protons and improving the selectivity of the proton exchange membrane. Therefore, the construction of the high-selective proton transfer channel is the most important research topic in the direction of the proton exchange membrane. The self-assembly of the proton transfer channel in the proton exchange membrane is realized by adjusting the microstructure of the proton transfer function polymer, and the selectivity of the proton exchange membrane can be further improved by optimizing the microstructure of the multi-stage proton transfer channel in the proton exchange membrane. The specific content of the study is as follows: 1. The research confirms that the hyperbranched polyetheramine proton exchange membrane can effectively reduce the fuel penetration and improve the proton conductivity. the proton exchange membrane exhibits a resistance to alcohol that is at least 15 times higher than nafion 117. On this basis, a new concept _ multi-stage proton transfer channel (HPCCs) is proposed for the first time. In these HPCCs, the proton transfer channel consisting of the high-density sulfonic acid groups inside the hyperbranched polyetheramine molecule is referred to as a primary proton transfer channel (FOPCC). In addition, the formation of a rich hydrogen bond network between the functional groups of the hyperbranched polyylamine molecules and the activated water molecules is referred to as a secondary proton transfer channel (SOPCC). The highly effective proton transfer performance (0.282S/ cm, 80oC) is demonstrated by the synergistic effect of the primary and secondary proton transfer channels. the invention realizes the optimization of the multi-stage proton transfer channel by adjusting the nano-structure of the synthetic hyperbranched polyetheramine molecular monomer, thereby reducing the methanol permeability of the proton exchange membrane, and simultaneously improving the selectivity of the proton exchange membrane by more than 1. This paper further enhances the resistance of the membrane by adjusting the microstructure of the first-order proton transfer channel. A series of co-mixed membranes were prepared by casting two kinds of polymers with different mass ratios with the solution casting method. because the density of the sulfonic acid groups-SO3H in the two polyetheramine macromolecules is different, the regulation of the primary proton transfer channel in the proton exchange membrane can be realized by adjusting the proportion of the two molecules in the blending membrane, so as to realize the optimization of the proton exchange membrane resistance alcohol and the selection performance. In this paper, the micro-structure of the two-stage proton transfer channel in the multi-stage proton transfer channel is optimized, and the hydrogen bond strength and water-retaining property of the second-stage proton transfer channel are changed by a gentle method, thus the overall performance of the proton exchange membrane is optimized. First, the hyperbranched polyetheramine macromolecules with different functional groups (-COOH and-NH2) and similar in size are designed and synthesized, and the two polymer macromolecules are prepared into the composite membrane according to different proportions. the micro-structure of the two-stage proton transfer channel in the blending film is adjusted by adjusting the proportion of the two polyetheramine macromolecules, the selectivity of the proton exchange membrane is 1 to 7 times higher than that of the Nafion 117, the application field is extended from a direct methanol fuel cell to an oxygen-oxygen flow cell that is also highly selective to a very high selectivity. The dense structure of the multi-stage proton transfer channel in the hyperbranched polyetheramine effectively prevents the penetration of the oxygen ions. Compared with the Nafion 117 membrane, the hyperbranched polyetheramine proton exchange membrane exhibits good proton/ polar ion selectivity, a high of 14. 4-104S. s/ cm3, 3-fold higher than that of the Nafion 117 membrane, and 5, due to the good chemical stability of the polycarbodiimide, In this paper, a hyperbranched polycarbodiimide is designed and synthesized for the construction of high-selectivity multi-stage proton transfer channels. The mechanical properties of the polycarbodiimide proton exchange membrane were 25% higher than that of polyalicyclic amine. the methanol permeability through the blend membrane was so low that the instrument could not be detected with the instrument. To sum up, a high-selectivity proton exchange membrane is obtained by a macromolecular microstructure design to obtain a high-selectivity proton exchange membrane, and at the same time, the proton exchange membranes exhibit good mechanical properties. This paper provides a reference for the development and research of a new type of proton exchange membrane for direct methanol fuel cell and oxygen-oxygen flow cell.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM911.4

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