【作者】 张飞；

【导师】 Andrew Baker；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2016， 硕士

【摘要】 直接甲醇燃料电池是燃料电池的一种,由于其具有能量密度高,成本低,组装简单,燃料可再生,电源移动方便等优点,因此可广泛应用于日常生活中。例如它可作为便携式电源,新能源汽车/船只,供电站等,因此对它的研究也正日渐加深。直接甲醇燃料电池的核心部件为电池内部的质子交换膜。目前主要材料为美国杜邦公司生产的Nafion质子交换膜,但是这种质子交换膜因存在甲醇渗透率过高以及在高温/含水量低的情况下质子交换膜质子导电率低的问题,所以对其进行改性便显得很有必要。本文中我们以先前对Na-X型沸石和NH₄-X型沸石研究为基础,深入研究亚微米尺寸H-X型沸石对复合质子交换膜的各项性能影响。用来作为掺杂材料以提高复合质子交换膜的选择性。我们用水热法合成制备出尺寸为30-50 nm,500-700 nm,1-1.5μm的Na-X型沸石,先将其转化为NH₄-X型沸石,然后再转化为H-X型沸石。掺杂不同种类的沸石,通过溶液重铸法制备出相应的Nafion复合质子交换膜。对制备出的沸石材料以及复合质子交换膜进行XRD,SEM/EDS,FT-IR,TGA/DSC等分析方法对其表征和分析。同时对复合质子交换膜的吸水性,离子交换量进行测试,我们也要完成对质子交换膜的甲醇渗透性以及质子导电性的测试,最后对质子交换膜组装成单电池用2mol/L的甲醇进行测试。测试结果表明掺杂沸石后的质子交换膜的吸水能力、离子交换容量、甲醇渗透率、质子导电率在与纯Nafion质子交换膜的这些性能相比都有了不同程度的提升。NH₄-X/Nafion复合质子交换膜的吸水能力、甲醇渗透率整体上要比H-X/Nafion的复合质子交换膜要好,但是离子交换容量和质子导电率方面较弱。当沸石的加入量为2.5wt%时其复合质子交换膜的选择性整体上比含量为5wt%的要高,相比于未经改性的质子交换膜,复合质子交换膜的甲醇渗透率下降了一半以上,而且复合质子交换膜的选择性也提高到了8倍左右。在沸石含量为2.5wt%的NH₄-X/Nafion复合质子交换膜和H-X/Nafion的复合质子交换膜组成的单电池的性能在80℃时是纯Nafion质子交换膜的两倍以上,表明了沸石的加入确实提高了DMFC的性能表现。对整体的实验进行总结我们得知,选择性方面在含量为2.5wt%的亚微米尺寸的NH₄-X和H-X两种沸石要优于其他几种沸石,通过测试发现所获得的单电池性能是最好的,其能量密度分别达到了127 mW/cm2和114 mW/cm2。这些结果表明在单电池测试中复合质子交换膜的性能和纯Nafion质子交换膜相比得到了提升。更多还原

【Abstract】 A direct methanol fuel cell（DMFC） has the advantages of high energy density, low cost, simple assembly, and as a renewable power source it can be widely used in daily life, e.g. a portable power source, vehicles（cars and boats）, and even power plants. The proton exchange membrane is the core part of direct methanol fuel cell and, at present, Du Pont`s Nafion is the main material used for a DMFC membrane. There are some problems with Nafion such as high methanol permeability and the proton conductivity is too low at high temperature and or low water content so it is necessary to modify it.This report is an extension of previous work that used different sized particles of Na-X and NH<sub>4</sub>-X type zeolites as a filler in Nafion. A hydrothermal method was used to make three size ranges; 30-50nm（nano）, 500-700nm（sub-micron）, and 1-1.5μm（micron） of Na-X zeolite which were then converted into NH<sub>4</sub>-X and H-X zeolite. After converting to NH<sub>4</sub>-X and H-X these were dispersed into Nafion solution at 2.5wt%, 5wt% loadings and then solution cast to make composite membranes. The zeolites were characterized by XRD, TGA/DSC, SEM/EDS, FTIR, and the composite membranes were characterized by FTIR, SEM, TGA, and water uptake, IEC, conductivity, permeability, and then assembled into a single cell to test the membranes’ performance in a DMFC using 2mol/L methanol.The test results show that NH<sub>4</sub>-X/Nafion composite membranes` have higher water uptake and lower permeability than H-X/Nafion composite membranes` but the ion exchange capacity and proton conductivity are higher for H-X/Nafion. Compared with pure Nafion membranes, the permeability of the composite membranes is decreased by over 50%, and the selectivity has improved eight times more than that of pure Nafion membranes. The results from DMFC single cell tests show that 2.5wt% loading tends to give better results than 5wt% loading. The single cell DMFC test results show the maximum value of power density for pure Nafion occurs at 80 ℃ but for 2.5wt% NH₄-X/Nafion and 2.5wt% H-X/Nafion composite membranes the maximum power density values occur at 80℃（the maximum temperature available） and are more than twice that of pure Nafion at 80℃.The results obtained here show the optimum zeolite size is submicron（500-700nm） and when loaded at 2.5wt%; NH₄-X/Nafion and H-X/Nafion composite membranes have the best single cell performance with a power density of 127 m W/cm2 and 114 m W/cm2 respectively. These results confirm an enhanced performance of the proton exchange membrane in a DMFC single cell when compared to pure Nafion.更多还原