高性能Pd催化剂的制备及其甲酸氧化催化行为研究

发布时间：2018-05-18 04:43

本文选题：燃料电池 + 直接甲酸燃料电池　；参考：《西南大学》2017年硕士论文

【摘要】：直接甲酸燃料电池(Direct formic acid fuel cells,DFAFCs)具有能量转换效率高,安全无毒而且环境友好等优点,在汽车动力以及便携式电源等方面具有广泛的应用前景。然而,DFAFCs常用的阳极Pd/C催化剂活性和稳定性不够优良,成为限制其商业化发展的重要因素。纳米科技的进步和深入,发展了在相关尺度范围内设计和制备高性能催化剂的有效方法。均匀分散的小粒径Pd纳米颗粒在提高材料利用率的同时展现出更高的电化学活性比表面积,而特殊纳米结构Pd催化剂粗糙的表面和多孔的结构通常存在大量的缺陷——提供丰富的扭结原子作为催化活性位点,从而有利于甲酸氧化过程中电极过程动力学的提升。然而,合成高性能特殊纳米结构的Pd催化剂仍然在基础研究和技术方面面临着很大挑战。本论文从调控催化剂形貌、尺寸等方面入手,设计并制备了具有高性能的均匀超细Pd纳米催化剂以提升催化性能。借助透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线能谱仪(EDS)等对所制备的催化剂的结构、形貌进行表征,通过循环伏安法(CV)和计时-电流法(i-t)等测试技术对其电化学行为和性能进行了详细的对比和分析。实验结果表明,聚二烯丙基二甲基氯化铵(PDDA)协助CO还原法制备均匀超小Pd纳米晶/石墨烯催化剂,由于其多孔结构载体石墨烯与表面洁净、超小且均匀分散的Pd纳米晶协同催化作用,对甲酸氧化展现出比商业化Pd/C催化剂更优良催化性能。而多枝化Pd纳米枝晶因其高度枝化且粗糙的表面,提供了丰富的扭结和台阶原子作为活性位点,以及它具有独特的多孔结构和高的可接触表面积促进了电化学动力学过程,在展现出比Pd/C催化剂更优异甲酸氧化行为催化性能的同时,为甲酸氧化催化过程提出了一些科学性见解。本论文内容共分以下五章:第一章综述简要概括了燃料电池的发展历程、原理、分类、性能和优势等,对DFAFCs的工作原理以及相应催化剂分别进行了介绍,同时也概述了一些常见催化剂的制备方法。最后对本论文的研究意义和主要内容进行了论述。第二章实验设计、材料表征及电化学测试技术本章归纳了实验过程中常用的实验仪器设备和主要实验试剂,介绍了研究和分析DFAFCs催化剂所使用的主要物理表征手段和电化学测试技术,描述了工作电极的制备过程。第三章PDDA协同下的CO还原法制备超小Pd纳米晶/石墨烯催化剂及其甲酸氧化催化行为的研究石墨烯(Graphene)具有较高比表面积、导电性优良和电化学稳定的特点。本章采用PDDA修饰Graphene,并利用CO作为还原剂在其表面均匀沉积了平均粒径为3.4 nm的Pd纳米晶——Pd@PDDA-G催化剂。结合催化剂物理表征以及电化学测试技术分析,与商业化的Pd/C催化剂相比,Pd@PDDA-G催化剂展示出更高的电化学活性比表面积和标准交换电流密度、更低的电荷转移电阻(Rct)以及更好的稳定性,从而在作为DFAFCs阳极催化剂方面具有更广阔的应用前景。我们认为,高导电性能的多孔结构载体Graphene与表面洁净、超小且均匀分散的Pd纳米晶协同催化作用是Pd@PDDA-G催化剂体现出优良催化性能的重要原因,同时本章研究为电极表面纳米结构催化剂的甲酸氧化催化反应提供了一些科学性见解。第四章多枝化Pd纳米枝晶合成及其甲酸氧化催化行为研究采用一种简易的方法制备了均匀分散且高度枝化的Pd纳米枝晶(Pd-NDs)——独特的多孔结构和粗糙的表面,并对该催化剂的甲酸氧化催化行为进行了研究。研究发现:苯甲醇和甲酸的体积比在制备独特纳米结构的Pd-NDs催化剂中扮演者重要的角色,而聚乙烯吡咯烷酮(PVP)浓度则是调控Pd-NDs粒径大小并实现催化剂尺寸可控的重要因素。通过电化学测试发现,Pd-NDs/C催化剂展现出比Pd/C催化剂更高的峰电流密度、催化活性以及更好的稳定性。本章工作中多枝化Pd纳米枝晶合成条件温和,操作简单,重复性强,因此有利于大规模范围的应用,同时该合成方法低毒环保,可以用于制备其它金属催化剂。第五章结论和工作展望本章对论文进行了总结,并对未来研究的方向做了进一步的展望。
[Abstract]:The direct formic acid fuel cell (Direct formic acid fuel cells, DFAFCs) has the advantages of high energy conversion efficiency, safety and innocuity and environment friendly and so on. It has extensive application prospects in automobile power and portable power supply. However, the activity and stability of the anode Pd/C catalyst commonly used in DFAFCs are not good enough to restrict its commercialization. An important factor in development. The progress and depth of nanotechnology has developed an effective method for the design and preparation of high performance catalysts in the related scale. The homogeneous dispersed small particle size Pd nanoparticles exhibit higher electrochemical activity specific surface area while increasing the material utilization, while the special nano structure Pd catalyst has a rough surface. The porous structure usually has a large number of defects - providing a rich kink atom as a catalytic active site, which is conducive to the improvement of the kinetics of the electrode process during the oxidation of formic acid. However, the synthesis of Pd catalysts for high performance special nanostructures is still facing great challenges in basic research and techniques. The structure and morphology of the prepared catalysts were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X ray diffractometer (XRD), X ray spectrometer (EDS), etc. by means of transmission electron microscope (TEM), and the structure and morphology of the prepared catalysts were characterized by means of circulation. The electrochemical behavior and properties were compared and analyzed by voltammetry (CV) and timing current method (I-T). The results showed that polydiallyl two methyl ammonium chloride (PDDA) assisted CO reduction in the preparation of homogeneous super small Pd nanocrystalline / graphene catalyst, because the porous structure carrier graphene was clean and ultra small. The uniformly dispersed Pd nanocrystals co catalyzed the oxidation of formic acid better than commercialized Pd/C catalysts. The polycrystalline Pd dendrites provided rich kinks and step atoms as active sites because of their highly branched and rough surfaces, and it had a unique porous structure and a high contact table. The area promotes the electrochemical kinetic process and presents some scientific views for the oxidation of formic acid at the same time that the oxidation behavior of formic acid is more excellent than the Pd/C catalyst. The content of this paper is divided into five chapters: the first chapter briefly summarizes the development process, principle, classification, performance and advantages of the fuel cell. The working principle of DFAFCs and the corresponding catalyst are introduced, and the preparation methods of some common catalysts are also outlined. Finally, the significance and main contents of this paper are discussed. The second chapter of the experiment design, material characterization and electrochemical testing technology summarizes the experimental instruments used in the experimental process. Preparation and main experimental reagents, the main physical characterization means and electrochemical testing techniques used for DFAFCs catalysts are introduced and analyzed. The preparation process of working electrodes is described. The preparation of ultra-small Pd nanocrystalline / graphene catalysts by the CO reduction method under the synergy of third chapter PDDA and the study of methenoic acid oxidation catalytic behavior of graphene (Graphene) It has high specific surface area, excellent electrical conductivity and electrochemical stability. This chapter uses PDDA to modify Graphene, and uses CO as a reducing agent to evenly deposit the Pd nanocrystalline - Pd@PDDA-G catalyst with an average particle size of 3.4 nm on its surface. It combines the physical characterization of the catalyst as well as the electrochemical test technology analysis, and the commercial Pd/C catalysis. The Pd@PDDA-G catalyst shows a higher electrochemical activity than the surface area and the standard exchange current density, lower charge transfer resistance (Rct) and better stability. Thus, it has a wider application prospect as a DFAFCs anode catalyst. We think that the porous structure carrier of high conductivity is Graphene and the surface. Clean, ultra-small and uniformly dispersed Pd nanocrystalline synergistic catalysis is an important reason for the excellent catalytic performance of Pd@PDDA-G catalyst. At the same time, this chapter provides some scientific opinions for the oxidation of formic acid on the surface of nano structure catalyst on the electrode surface. Fourth chapter the synthesis of polycrystalline Pd dendrites and the oxidation catalysis of formic acid A simple method was used to prepare a uniformly dispersed and highly branched Pd dendrite (Pd-NDs) - a unique porous structure and a rough surface, and the catalytic behavior of the formic acid in the catalyst was studied. The volume ratio of benzyl alcohol and formic acid was found in the Pd-NDs catalyst for the preparation of the unique nanostructure. The concentration of polyvinylpyrrolidone (PVP) is an important factor in regulating the size of Pd-NDs particles and realizing the controllable size of the catalyst. The electrochemical test shows that the Pd-NDs/C catalyst exhibits higher peak current density, catalytic activity and better stability than the Pd/C catalyst. In this chapter, the multi branched Pd Na The synthesis of rice dendrites is mild, simple in operation and strong in repeatability. Therefore, it is beneficial to large-scale application. At the same time, the synthetic method is low toxic and environmentally friendly and can be used in the preparation of other metal catalysts. The fifth chapter and the work prospect are summarized in this chapter, and the direction of future research is further prospected.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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