纳米多孔核—壳结构氧还原电催化剂的制备、表征与性能研究

发布时间：2018-02-24 23:05

本文关键词： 燃料电池氧还原薄膜电催化剂铂单原子层　出处：《天津理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：在各种绿色能源技术中,质子交换膜燃料电池(proton exchange membrane fuel cells,PEMFCs)可以高效地将化学能转换为电能。由于燃料电池具有低碳或零碳排放的特点,因此在过去十年内受到了科研工作者的广泛关注。但是燃料电池的大规模商业化应用却受到高Pt催化剂需求量的影响而受到了严重的阻碍,因为Pt催化剂不仅价格昂贵,且资源有限。脱合金纳米多孔金属由于具有特殊的结构和电化学性能而在燃料电池的开发应用上具有潜在价值。通过在适宜的电解液中腐蚀商业化的合金薄膜得到的纳米多孔金(nanoporous gold,NPG),这种材料本身就可以作为一些电极反应的催化材料,进一步对其表面功能化,所得到的纳米多孔金基催化剂对燃料电池而言更加具有独特的结构优势,例如高比表面积,高电子传导率,高稳定性和高的贵金属利用率。因此,本论文以纳米多孔金为基底,通过不同方法制备原子层级Pt壳催化剂,并探究它们的形貌与性能,以及在电催化和燃料电池领域的应用。具体研究内容如下:(1)通过Cu欠电位沉积-原位置换的方法,构建了一种自支撑的纳米多孔金属电催化剂,它有着亚纳米厚的PtPd壳,开始的ORR质量活性在0.9V(vs RHE)时达到了1.140 A mgPt~(-1)。在30000个电势循环后质量活性达到了1.471 A mgPt~(-1),并且稳定至100000个电势循环。利用一氧化碳扫除和甲酸电氧化实验推测出活性改变的起源------表面结构演化。从开始的PtPd合金壳到表面富铂的三元合金表面结构,再到最后的统一稳定的PtPdAu三元合金结构。(2)通过化学还原沉积的方法,在纳米多孔金表面修饰原子层级的Pt壳层,成功制备了NPG-Pt氧还原电催化剂。该催化剂在酸性电解质中对于氧还原反应有着优秀的催化活性,与商业Pt/C催化剂相比,该催化剂可以在0.9 V(vs RHE)实现0.44 A mgPt~(-1)的质量活性,相比商业催化剂,催化活性增强近2.8倍。此外,该催化剂材料显示出卓越的稳定性。经过30000个电势循环扫描后,仅有17 mV半波电位负移。最后,将NPG-Pt催化剂材料应用于直接甲醇燃料电池和氢氧燃料电池中,结果显示该类型催化剂在提高Pt的利用率,降低Pt载量方面具有显著优势,归一到单位Pt质量的电池最大功率密度相对于商业催化剂分别具有20倍和1.7倍的提高。
[Abstract]:Among various green energy technologies, proton exchange membrane fuel cells can efficiently convert chemical energy into electric energy. However, the large-scale commercial use of fuel cells has been seriously hampered by the demand for high Pt catalysts, because Pt catalysts are not only expensive. Due to its special structure and electrochemical properties, dealloyed nano-porous metal has potential application in fuel cell development and application. To the nanometer porous gold, the material itself can be used as a catalytic material for some electrode reactions. For further surface functionalization, the resulting nano-porous gold-based catalysts have unique structural advantages for fuel cells, such as high specific surface area, high electron conductivity, high stability and high noble metal utilization. In this paper, nano-porous gold was used as the substrate to prepare Pt shell catalysts at atomic level by different methods, and their morphology and properties were investigated. And its application in the field of electrocatalysis and fuel cell. The specific research contents are as follows: (1) A self-supporting nano-porous metal electrocatalyst was constructed by Cu under-potential depositation-in-situ displacement method, which has a subnanometer-thick PtPd shell. The initial mass activity of ORR reached 1.140A mgPtttl after 30000 potential cycles, and stabilized to 100000 potential cycles. The activity was estimated by carbon monoxide cleaning and formic acid electrooxidation experiments. Evolution of surface structure from the beginning of the PtPd alloy shell to the surface structure of the platinum-rich ternary alloy, Finally, the uniform and stable structure of PtPdAu ternary alloy. 2) by chemical reduction deposition, the Pt shell at atomic level is modified on the surface of nano-porous gold. NPG-Pt oxygen reduction electrocatalyst was successfully prepared. The catalyst has excellent catalytic activity for oxygen reduction in acidic electrolytes. Compared with commercial Pt/C catalyst, the catalyst can achieve 0.44 A mg PtT-1) mass activity in comparison with commercial Pt/C catalyst. The catalytic activity of the catalyst is nearly 2.8 times higher than that of the commercial catalyst. In addition, the catalyst material shows excellent stability. After 30000 potential cycles, only 17 MV half-wave potential is negatively shifted. The application of NPG-Pt catalyst material in direct methanol fuel cell and hydrogen oxygen fuel cell shows that this type of catalyst has significant advantages in increasing Pt utilization and reducing Pt load. The maximum power density of the cells normalized to Pt mass was increased by 20 times and 1.7 times than that of commercial catalysts, respectively.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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