Ni@Pt核壳结构燃料电池催化剂的制备及催化性能研究

发布时间：2018-04-02 04:40

  本文选题：PtNi纳米粒子　切入点：核壳结构　出处：《昆明理工大学》2017年硕士论文

【摘要】：质子交换膜燃料电池是最有可能广泛应用的低污染高效率能源转换装置。该装置的成本主要在催化剂上,由于催化剂Pt价格昂贵而且资源稀少,燃料电池的研究发展依赖于获得低铂高活性的催化剂。贵金属及合金催化剂的活性与其形貌、晶体结构、表面状态、颗粒尺寸、负载分散性等因素有关。目前已有大量研究对铂进行合金化处理降低Pt在催化剂中的用量,但这仍不足以将燃料电池的成本降低到期望水平。研究显示对纳米颗粒的形貌调控可以有效提高催化剂的表面积和高指数晶面,从而提高电化学活性。另外,由于催化剂在使用时主要是在表面发生催化反应,颗粒内部的贵金属处于无用状态,核壳结构正是针对这一特点设计的,可以有效降低铂的使用量。本研究采用PtNi系列合金作为研究对象来调控获得到得高活性的催化剂。研究采用两步法调控得到多种形貌PtNi纳米颗粒。研究了 Pt/Ni的摩尔比对形貌的影响。研究发现:只在Pt/Ni合金摩尔比为1:1的时候,才会倾向于多枝状结构的生成;枝状组织是特定晶体方向生长,只含有铂元素;加入CTAB和二苯醚都促进得到核壳型结构纳米粒子,壳层较为均匀;Pt/Ni为1:3时核壳结构的表层铂的层厚度在6nM左右。本论文还研究了热处理温度、时间、气氛对PtNi/C催化剂电化学活性影响。在N2/H2气氛下400℃/4h热处理后PtNi获得最佳的氧还原反应活性,半波电位为0.74V,电流密度为4.45mA·cm过长的加热时间会导致金属粒子的团聚,过高的热处理温度则引起纳米PtNi的长大。本论文采用XPS分析不同状态下PtNi/C催化剂表面铂的氧化态和Pt/Ni比。在N2/H2气氛下混合气体中热处理可以降低表面氧化态数量,并且在某些条件下可以完全得到金属还原态。表面Pt/Ni比表明PtNi纳米粒子发生了表面偏析,形成了合金核壳结构。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) is the most widely used energy conversion device with low pollution and high efficiency. The development of fuel cells depends on the preparation of catalysts with low platinum and high activity. The activity of noble metal and alloy catalysts and their morphology, crystal structure, surface state, particle size, A lot of research has been done to reduce the amount of Pt in the catalyst by alloying platinum. However, this is not enough to reduce the cost of fuel cells to the desired level. Due to the catalytic reaction on the surface of the catalyst, the precious metal in the particle is useless, so the core-shell structure is designed according to this characteristic. In this study, PtNi series of alloys were used as the research object to control the catalyst with high activity. A variety of PtNi nanoparticles with different morphologies were obtained by two-step method. The structure of Pt/Ni was studied. The effect of molar ratio on morphology. It was found that when the molar ratio of Pt/Ni alloy was 1:1, The dendritic structure grows in a specific crystal direction and contains only platinum elements. The addition of CTAB and diphenyl ether promotes the formation of core-shell structure nanoparticles. The thickness of platinum layer of core-shell structure is about 6nM when the thickness of Pt / Ni is 1:3. The temperature and time of heat treatment are also studied. The effect of atmosphere on the electrochemical activity of PtNi/C catalyst. After heat treatment at 400 鈩，

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