聚醚砜基改性阴离子交换膜的制备及性能研究

发布时间：2018-03-19 22:33

本文选题：燃料电池　切入点：复合膜　出处：《东北师范大学》2017年博士论文　论文类型：学位论文

【摘要】：燃料电池是一种高效、环保的新型能源转化装置,能够将化学能直接转化为电能且不受热机卡诺循环机理的限制,相比传统化石能源的使用具有更高的能源利用率。聚合物电解质膜作为燃料电池的核心部件,能够起到阻隔燃料、负载催化剂以及传导离子的作用,因此其性能的好坏直接决定了燃料电池的使用效果。通常按照所传导离子的种类将聚合物电解质膜分为质子交换膜(PEMs)和碱性阴离子交换膜(AEMs),其中PEMs由于其组成电池具有功率密度高、响应速度快等优点,因此在近几年的发展较为迅速。美国杜邦公司生产的全氟磺酸膜(Nafion)作为商业化的质子交换膜产品,具有较高的电导率和化学稳定性,但其离子传导性能严重依赖膜的吸水率,在高温、低湿环境下性能较差且造价昂贵,因此需要进一步改进。基于以上问题,近期人们开始关注并开发AEMs,由于其具有电极氧化还原反应速率高、低燃料渗透以及避免使用贵金属催化剂等优势,因此相对PEMs具有更大的发展潜力。但AEMs所传递离子的扩散系数普遍低于质子,导致了AEMs的离子传导率较低,目前很少有综合性能超过Nafion膜的阴离子交换膜产品。此外,AEMs中的季铵盐基团在碱性环境下容易发生降解从而影响使用性能,因此对AEMs进行改性研究并弥补上述缺点具有重要的科学意义。在本论文的研究工作中,选择以聚醚砜类聚合物材料作为AEMs的基质,分别利用不同的方法对AEMs进行改性,力求使改性阴离子交换膜具有较高的离子传导能力和良好的化学稳定性。具体的工作主要分为以下四个部分:1.合成了含芴结构的聚醚砜类聚合物基质(PFSU),通过使用NBS溴代、季铵盐化等方法对其聚合物侧链进行改性,从而得到了含有叠氮基团的季铵盐化聚醚砜(AMPFSU)。其次,以设计合成的不同结构和长度的双官能度炔烃为交联剂,通过点击化学反应对AMPFSU膜进行交联改性得到一系列交联型阴离子交换膜。结果证明,交联能够促进聚合物膜内部紧密堆积从而改善膜的机械性质,随着交联剂极性的增加,交联膜的吸水率与溶胀率等性质都会得到提高;AEMs的阻醇性和化学稳定性同时随交联而得到增强;对于离子传导率而言,多数交联膜的电导率相比交联前有很大的降低,但d-CPFSU-1膜由于内部形成了均匀的纳米微相分离结构,因此其在80oC的OH-电导率反而提高到193.95mS cm-1,说明交联剂的结构对AEMs的微观相区结构和性能具有重要影响。2.利用Hummers法合成了氧化石墨烯(GO),并通过水热还原反应等方法对GO进行表面改性,利用可逆加成断裂链转移活性自由基聚合(RAFT)法将苄基氯苯乙烯单体接枝聚合在还原石墨烯上,从而得到了聚合物刷修饰的还原石墨烯(QPbGs)。将不同含量的QPbGs以直接共混的方式引入到氯甲基化聚醚砜(CMPSU)中,所得到的聚合物膜经过季铵盐化和阴离子置换等步骤最终制得了一系列改性复合阴离子交换膜。研究结果发现QPbGs的引入不但可以提高复合膜的IEC值、吸水率、溶胀率、阻醇性以及机械强度等性质,在改变膜的内部微观相结构的同时还能够改善复合膜的离子传导性能,其在80oC下的OH-电导率最高可达到91.6m S cm-1。当QPbGs引入过量时,会伴随着无机掺杂相的团聚效应,结果降低了复合膜的机械性质与离子传导率。3.合成了侧链含有叠氮基团的季铵盐化聚醚砜(AMPSU)和还原石墨烯(rGO),然后将二者直接共混制备出一系列交联型复合阴离子交换膜,在不额外使用交联剂和牺牲离子传导基团的情况下,通过直接加热的方法使聚合物通过侧链上叠氮基团和rGO结构中的不饱和双键之间进行氮烯加成反应从而构筑交联网络结构。结果发现膜的性质如吸水率、溶胀率都随交联而显著降低,从而导致了膜的离子电导率下降。然而发现当只有少量rGO(0.5wt%)被掺杂到膜中引发交联便可以使所得交联膜的甲醇渗透率降低两个数量级,同时增强膜的机械强度和热稳定性。此外,交联膜在芬顿试剂中能够保持稳定存在,在60oC 1 M KOH溶液中能够保持稳定500小时。因此,我们制备的交联型rGO复合膜在阴离子交换膜燃料电池中具有很大的发展潜力。4.通过无水柠檬酸和乙二胺的水热反应制备出表面具有胺基官能团的碳点(CDs),再利用氯化缩水甘油基三甲基铵(GDTMAC)对其表面进行功能化从而得到季铵盐化的碳点(QCDs)。最后将不同含量的QCDs引入到咪唑化聚醚砜基质(Im-PSU)中制备了一系列新型复合阴离子交换膜。初步的研究结果表明:所制备的QCDs具有小尺寸的纳米结构(3-4 nm),将其添加到咪唑化聚醚砜基质中能够有效地提高复合膜的IEC、吸水率、溶胀率、OH-电导率以及氧化稳定性。进一步的研究工作仍在进行中。
[Abstract]:Fuel cell is a highly efficient, environmentally friendly new energy conversion device, can convert chemical energy directly into electrical energy and is not affected by the mechanism of the Kano cycle limit, compared with the traditional fossil energy has higher energy efficiency. As a core component of polymer electrolyte membrane fuel cell, to obstruct fuel load effect of catalyst and ion conductivity, so its performance directly determines the quality of the fuel cell performance. Usually according to the kind ion conductive polymer electrolyte membrane will be divided into the proton exchange membrane (PEMs) and alkali anion exchange membrane (AEMs), which PEMs because of its battery with high power density, high response speed fast, so in recent years the development of more quickly. The perfluoro sulfonic acid membrane America produced by DuPont Co (Nafion) as the commercialization of the proton exchange membrane products with high conductivity The rate of water absorption and chemical stability, but its performance is heavily dependent on membrane ionic conduction rate in high temperature, low humidity environment of poor performance and high cost, so it needs further improvement. Based on the above problems, recently people began to pay attention to and the development of AEMs, because of its electrode redox reaction rate is high, low permeability and avoid the use of expensive fuel metal catalyst and other advantages, so PEMs has greater development potential. The diffusion coefficient of AEMs ion transfer but is generally lower than the proton, lead ion conduction AEMs rate is low, there is little comprehensive performance than Nafion membrane anion exchange membrane products. In addition, quaternary ammonium groups in AEMs easily in the alkaline environment the degradation of thus affecting the performance, so the modification of AEMs research and has important scientific significance to make up for the disadvantages. In this paper, choose from polyether Sulfone polymer material as the substrate of AEMs, respectively, using different methods to modify AEMs, ionic conductivity makes the modified anion exchange membrane has high and good chemical stability. The specific work is divided into the following four parts: 1. synthesis of polyether sulfone polymer matrix containing fluorene structure (PFSU), through the use of NBS bromide, the modification of polymer side chain quaternary ammonium salt method, obtained containing azide group of quaternary ammonium salt of polyethersulfone (AMPFSU). Secondly, two different structure and length of officer in the synthesis to alkynes as crosslinking agent for AMPFSU film crosslinking modification to obtain a series of cross-linked anion exchange membrane by click chemistry. The results prove that the crosslinked polymer membrane can promote internal close packing so as to improve the mechanical properties of the film, with the increase of the polarity of the crosslinking agent, water absorbent crosslinked membrane The rate and swelling properties will be improved; AEMs alcohol resistance and chemical stability as the crosslinking is enhanced; the ionic conductivity, conductivity of most crosslinked films compared before the crosslinking has been greatly reduced, but the d-CPFSU-1 film due to internal formation of nano uniform micro phase separation structure, so the 80oC OH- 193.95mS cm-1 to improve the conductivity but, illustrate the structure and performance of micro structure of crosslinking agent on AEMs phase plays an important role in.2. by the method of Hummers graphene oxide (GO) was synthesized by hydrothermal reduction reaction, and methods of surface modification of GO, addition fragmentation chain transfer radical polymerization the use of reversible (RAFT) method of polymerization of ethylene monomer grafted benzyl chlorobenzene in the reduction of graphene, resulting in reduced graphene modified polymer brushes (QPbGs). The different contents of QPbGs were mixed by direct approach The chloromethylation of polyethersulfone (CMPSU), the polymer film obtained by quaternary ammonium salt and the anion exchange step finally made a series of modified composite anion exchange membrane. Results showed that the introduction of QPbGs can not only improve the composite film IEC value, water absorption rate, swelling rate, resistance to alcohol and the mechanical properties such as strength, in the internal change of membrane ionic conductivity of the micro phase structure also can improve the composite membrane, the 80oC under the highest conductivity of the OH- when QPbGs introduced 91.6m S cm-1. excessive, will be accompanied by the agglomeration effect of inorganic doped phase, resulting in reduced side chain containing azide group the synthesis of Quaternary ammonium salt of polyethersulfone membrane mechanical properties and ionic conductivity of.3. (AMPSU) and reduced graphene (rGO), and two were directly prepared by blending a series of crosslinked composite anion exchange membrane, without additional use The crosslinking agent and sacrifice ion conduction group, by directly heating the polymer through the side chain of the azide group and rGO in the structure of unsaturated double bond nitrene addition reaction to construct cross-linked network structure. The results showed that the membrane properties such as water absorption and swelling rate were significantly decreased with increasing of crosslinking, which leads to the ionic conductivity of membrane decreased. However, when only a small amount of rGO (0.5wt%) was doped into membrane cross-linking can make the methanol permeability of the cross-linked membranes decreased by two orders of magnitude, while enhancing the mechanical strength and thermal stability of the film. In addition, the crosslinked films can keep stable in the presence of Fenton reagent. Can keep stable for 500 hours in the 60oC 1 M KOH solution. Therefore, we prepared crosslinked rGO composite membrane preparation membrane fuel cell.4. has great potential for development by anhydrous citric acid on anion exchange The hydrothermal method and ethylenediamine prepared with amine groups on the surface of carbon (CDs), using three methyl ammonium chloride glycidyl (GDTMAC) functionalized on the surface so as to obtain the quaternary ammonium salt of carbon (QCDs). The different content of QCDs into the matrix of imidazole polyether sulfone (Im-PSU) in the preparation of a series of new composite anion exchange membrane. The preliminary results show that the as prepared QCDs nanostructures with a small size (3-4 nm), will be added to the PES of imidazole matrix can effectively improve the composite membrane IEC, water absorption rate, swelling rate, OH- the electrical conductivity and oxidation stability. Further research work is still in progress.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ425.236;TM911.4

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