质子交换膜燃料电池膜电极及催化剂的研究

发布时间：2018-01-13 04:37

本文关键词：质子交换膜燃料电池膜电极及催化剂的研究　出处：《天津大学》2014年博士论文　论文类型：学位论文

【摘要】：质子交换膜燃料电池（PEMFC）具有清洁、高效、功率密度高、启动快等优点，在电动汽车、便携式和分布式电源设备等领域具有广阔的应用前景。但PEMFC膜电极的高成本和低稳定性严重地制约了其大规模商业化应用。本文从膜电极的制备、催化层的结构取向优化、高催化活性和高稳定性Pt催化剂的制备等方面对PEMFC进行了研究。提出了一种新的膜电极制备方法：使稀催化剂“墨水”直接在气体扩散层上干燥制备出气体扩散电极，然后再与膜热压制得膜电极。该方法制备过程简单，不需要特殊的仪器设备，催化层中的Pt载量能够较为精确地控制，具有相同制备参数的膜电极，其放电电流-电压曲线和功率密度曲线基本重合，实验具有很好的重复性。催化层中的Nafion含量为30-40wt%时，电池的最大功率密度可达900mW/cm2。利用电场的作用制备了结构取向的Pt/CNTs（Pt/碳纳米管）催化层。在Pt/CNTs催化剂“墨水”干燥过程中施加垂直向外电场，使CNTs载体沿着电场的方向定向排列，有利于提高催化层中Pt的利用效率、降低膜电极的内阻、促进反应气体的扩散和反应生成的液态水的及时排出。与无取向结构的Pt/CNTs催化层相比，CNTs载体定向排列的催化层具有高出约30%的电池峰功率密度。以耐腐蚀、导电性好、比表面积高、廉价易得的石墨纳米片（GNPs）为载体制备了Pt/GNPs催化剂。针对GNPs表面的化学惰性，利用芳香环π-π堆积的原理使1-芘甲酸吸附在GNPs的表面并为Pt提供成核点，，可以使沉积在GNPs表面的Pt纳米颗粒具有约2-3nm的均一尺寸，且空间分布均匀。通过1-芘甲酸对GNPs进行非共价修饰，所制备的Pt/GNPs催化剂具有较高的电化学比表面积和较好的电化学稳定性。使用一系列含不同苯环数和不同官能团的修饰物研究了修饰物与GNPs的π-π堆积作用力和其官能团对Pt在GNPs表面沉积的影响，并通过改变催化剂的制备条件研究了修饰物在Pt沉积过程中的作用机理。结果显示：修饰物与GNPs的π-π作用力较强且其官能团能够电离时才对Pt的沉积具有明显的辅助作用，另外，修饰物的不同不影响Pt纳米颗粒的晶体结构和催化剂的电化学稳定性。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) has the advantages of cleanness, high efficiency, high power density, fast start and so on, in electric vehicles. Portable and distributed power generation devices and other fields have broad application prospects, but the high cost and low stability of PEMFC membrane electrode seriously restrict its large-scale commercial application. The structure and orientation of the catalyst layer, the preparation of Pt catalyst with high catalytic activity and high stability were studied in this paper. A new preparation method of membrane electrode is proposed: the thin catalyst "ink" is used to prepare the gas diffusion electrode directly on the gas diffusion layer, and then the membrane electrode is prepared by hot pressing with the membrane. The preparation process is simple. The Pt load in the catalyst layer can be controlled accurately without special equipment. The discharge current-voltage curve and the power density curve of the membrane electrode with the same preparation parameters basically coincide. When the Nafion content in the catalyst layer is 30-40 wt%, the maximum power density of the cell can reach 900mW / cm ~ 2. The structure oriented Pt / CNT / carbon nanotube (CNT / CNT / CNT nanotube) catalyst layer was prepared by the electric field. The vertical electric field was applied during the drying process of the Pt/CNTs catalyst "ink". The orientation of CNTs carriers along the direction of electric field can improve the utilization efficiency of Pt in the catalyst layer and reduce the internal resistance of the membrane electrode. Promote the diffusion of the reaction gas and the timely discharge of the liquid water produced by the reaction, compared with the non-oriented structure of the Pt/CNTs catalytic layer. The CNTs carrier oriented catalytic layer has a peak power density of about 30%. The Pt/GNPs catalyst was prepared on the basis of high corrosion resistance, good electrical conductivity, high specific surface area and cheap and easy to obtain graphite nanoparticles. Based on the principle of aromatic ring 蟺-蟺 stacking, 1-pyrene formic acid is adsorbed on the surface of GNPs and provides nucleation point for Pt. The Pt nanoparticles deposited on the surface of GNPs have a uniform size of about 2-3 nm and uniform spatial distribution. GNPs was modified by 1-pyrene formic acid. The prepared Pt/GNPs catalyst has high electrochemical specific surface area and good electrochemical stability. The 蟺-蟺 stacking force of GNPs and the effect of functional groups on Pt deposition on the surface of GNPs were studied by using a series of modifiers containing different benzene rings and different functional groups. The mechanism of the modification in Pt deposition was studied by changing the preparation conditions of the catalyst. The results showed that:. When the 蟺-蟺 interaction force between the modifier and the GNPs is strong and its functional group can ionize, it has obvious auxiliary effect on Pt deposition. In addition, the crystal structure of Pt nanoparticles and the electrochemical stability of the catalyst were not affected by the modification.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM911.4;O643.36

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