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首页> 外文学位 >Development of Pt/CNT catalyst and transport-kinetic characterization of PEMFC catalyst layer.
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Development of Pt/CNT catalyst and transport-kinetic characterization of PEMFC catalyst layer.

机译：Pt / CNT催化剂的开发和PEMFC催化剂层的传输动力学表征。

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The electrochemical performance of a polymer electrolyte membrane fuel cell is known to be dominated by the cathode processes comprising the various reaction and transport steps in the overall oxygen electro-reduction to water occurring in the catalyst layer (CL). This thesis is concerned with one such transport process---oxygen transport in ionomer phase of the CL---and the synthesis/characterization of platinum catalyst on an alternative support---carbon nanotubes (CNT). Specifically, the objectives of the thesis are: (i) exploration of methods for determining the effective permeability of oxygen in the ionomer phase of the carbon-ionomer composite representing the PEMFC catalyst layer (ii) synthesis of Pt/CNT catalysts and characterization thereof.;An electrochemical method for determination of oxygen permeability in Nafion and Nafion-carbon composite films was explored. Since the method is suitable for dense films, mathematical model for data analysis had to be modified to allow treatment of porous films. Applying the modified model to the porous Nafion film, the oxygen permeation in the Nafion phase was found to agree with the literature data for oxygen permeation in Nafion membranes. However, no relationship between the effective permeability and ionomer content was found.;Two methods for synthesis of Pt/CNT catalysts were studied---the precipitation method and the colloidal/ethylene glycol method. Functionalization of CNTs was found to be critical to obtaining any significant amount of Pt deposition on CNT. The precipitation method did not yield reproducible results. Pt/CNT catalysts of desired properties were synthesized via the colloidal/EG method. It was found that a high pH of 8.5 to 10.5 resulted in smallest Pt particle size. The Pt particles size was determined to range 2-4 nm. The synthesized Pt/CNT catalysts were also tested in a fuel cell environment. Steady-state polarization curves in humidified H2/Air system were obtained that demonstrated performance comparable to commercial electrodes in that cell potential of greater than 0.6 V at current density of 800 mA/cm2 electrode area and a limiting current density of 1200 mA/cm2 electrode area were observed.
机译：已知聚合物电解质膜燃料电池的电化学性能主要由阴极工艺控制，该阴极工艺包括在将氧气整体还原成催化剂层（CL）中的水时进行的各种反应和运输步骤。本论文涉及一种这样的传输过程-CL的离聚物相中的氧气传输-以及在另一种载体上的铂催化剂的合成/表征-碳纳米管（CNT）。具体而言，本论文的目的是：（i）探索确定代表PEMFC催化剂层的碳-离聚物复合物的离聚物相中氧的有效渗透率的方法（ii）Pt / CNT催化剂的合成及其表征。 ；探索了一种电化学方法测定Nafion和Nafion-碳复合薄膜的透氧性。由于该方法适用于致密膜，因此必须修改数据分析的数学模型以允许处理多孔膜。将改进的模型应用于多孔Nafion膜，发现Nafion相中的氧渗透与Nafion膜中氧渗透的文献数据一致。然而，没有发现有效渗透率与离聚物含量之间的关系。；研究了两种合成Pt / CNT催化剂的方法-沉淀法和胶体/乙二醇法。发现CNT的功能化对于在CNT上获得任何大量的Pt沉积至关重要。沉淀法未得到可再现的结果。通过胶体/ EG法合成了具有所需性能的Pt / CNT催化剂。发现8.5至10.5的高pH导致最小的Pt粒度。 Pt粒径确定为2-4 nm。还在燃料电池环境中测试了合成的Pt / CNT催化剂。在加湿的H2 / Air系统中获得的稳态极化曲线显示出与商用电极相当的性能，在800 mA / cm2电极面积的电流密度和1200 mA / cm2电极的极限电流密度下，电池电位大于0.6 V观察区域。

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