碳载铂基直接甲醇燃料电池阳极电催化剂的制备和应用

发布时间：2018-03-04 08:20

  本文选题：直接甲醇燃料电池　切入点：阳极催化剂　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：直接甲醇燃料电池,是基于质子交换膜燃料电池技术的低温电池。甲醇直接进入燃料电池,不需要经过重整转换成氢的中间步骤。近来,由于直接甲醇燃料电池技术相对较为成熟且燃料来源丰富、储存安全,直接甲醇燃料电池研发引起了广泛关注。但真正实现商业化还是有较多的困难,催化剂技术即是其核心问题之一。本文以高活性、高稳定性低温燃料电池催化剂为目标,首先探索更优化的金属纳米粒子制备方法,再制备出性能优异的复合载体,之后利用所制备复合载体及Pt NPs制备40wt.%载量的催化剂,并对此过程进行深入研究。(1)当不使用高分子保护性试剂时,由于Oswald熟化作用,Pt纳米粒子(3nm)很容易发生聚结。但使用包覆性试剂时,又会遮挡Pt NPs的活性位,导致燃料电池催化剂活性不高。在本文中,我们开发了一种无机盐辅助柠檬酸还原法制备高分散和高稳定性Pt溶胶(2nm)的方法。添加无机盐后(在Pt NPs周围形成厚的双电层,稳定Pt溶胶)可显著减少柠檬酸的使用量(Cyt3-/Pt4+=1:1),因此不再需要后续加热去除碳载铂催化剂表面过量柠檬酸的操作。本文中借助Zeta电位、TEM测试和开路电位来表征Pt溶胶稳定性实属先例。所制得的Pt/C催化剂相比商业Pt/C催化剂有更高的甲醇氧化(以此反应作比照反应)活性。单独制备带正电的Ru纳米粒子和带负电的Pt纳米粒子,在室温下混合后,通过静电自组装成结构规整的PtxRuy纳米粒子。在所得催化剂PtxRuy/C中,CO溶出伏安的起始氧化电位和峰电位与Pt/Ru比值密切关联,这可能是Pt和Ru间不同的组装模式造成了不同的Pt、Ru粒子间距。Pt3Ru1/C的甲醇氧化质量比活性比商业Pt Ru/C催化剂的高112%。(2)为了改善电催化剂载体稳定性的问题,将纳米级Ti O2、乙酸钴和碳粉浸渍混合,在900℃还原性气氛中处理,当混合物中的乙酸钴高温分解后即生成复合载体,经XRD衍射分析得知组分为Ti O2-Co3O4-C(标记为CS)。通过计时电流测试,这种复合载体相比普通的炭黑在酸性条件下显示出了更强的抗腐蚀性或稳定性。利用该复合载体制备40.3wt.%的Pt/CS质子交换膜燃料电池催化剂,在0.5M硫酸溶液中进行的加速稳定性测试(AST)中显示,Pt/CS的ECSA在测试完后剩27.9%,而Pt/XC-72(39.5wt.%)的ECSA剩8.4%。另外经AST后TEM照片也可进一步证实Pt/CS有更强的抗Pt纳米粒子聚结的能力。在0.5M CH3OH和0.5M H2SO4溶液中测试甲醇氧化性能显示,相比于Pt/C,Pt/CS有更高的质量比活性和更慢的活性衰减速率。
[Abstract]:Direct methanol fuel cells are cryogenic cells based on proton exchange membrane fuel cell technology. Methanol enters the fuel cell directly without the intermediate steps of reforming to hydrogen. Because the technology of direct methanol fuel cell is relatively mature, the fuel source is abundant and the storage is safe, the research and development of direct methanol fuel cell has attracted wide attention. However, there are still many difficulties to realize the commercialization of direct methanol fuel cell. The catalyst technology is one of its core problems. In this paper, the high activity, high stability and low temperature fuel cell catalyst is taken as the target. Firstly, the more optimized preparation method of metal nanoparticles is explored, and then the excellent composite support is prepared. After that, the catalyst with 40wt.% loading was prepared by using the prepared composite support and Pt NPs, and the process was studied deeply when the polymer protective reagent was not used. Due to the maturation of Oswald, Pt nanoparticles can easily coalesce. However, the active sites of Pt NPs will be blocked when the coated reagent is used, which leads to the low activity of the fuel cell catalyst. We have developed an inorganic salt-assisted citric acid reduction method for the preparation of highly dispersed and highly stable Pt sols (2nm). Stabilization of Pt sol can significantly reduce the amount of citric acid used by Cyt _ 3-P _ t _ 4 / 1: 1, so the operation of removing excess citric acid on the surface of carbon-supported platinum catalyst is no longer needed. In this paper, Zeta potential Tem and open-circuit potential are used to characterize Pt dissolution. The stability of the colloid is a precedent. The prepared Pt/C catalyst has higher methanol oxidation activity than commercial Pt/C catalyst (the reaction is compared to the reaction). The Ru nanoparticles with positive charge and Pt nanoparticles with negative charge are prepared separately. After mixing at room temperature, the structured PtxRuy nanoparticles were self-assembled by electrostatic self-assembly. The initial oxidation potential and peak potential of CO stripping voltammetry in the obtained catalyst PtxRuy/C were closely related to the Pt/Ru ratio. It is possible that the different assembly modes between Pt and Ru result in the difference of PtN Ru particle spacing. Pt3Ru1C has higher methanol oxidation mass activity than commercial Pt Ru/C catalyst.) in order to improve the stability of electrocatalyst support, The nano-TiO _ 2, cobalt acetate and carbon powder were impregnated and treated in a reductive atmosphere at 900 鈩，

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