Fe,Co元素掺杂的纳米多孔Pt-Al金属间化合物及氧还原性能

发布时间：2018-01-17 16:26

本文关键词：Fe,Co元素掺杂的纳米多孔Pt-Al金属间化合物及氧还原性能　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：在环境污染日益严重,化石燃料极度匮乏的今天,寻找一种储量大、成本低、环境友好的新型能源是解决环境与能源问题的关键。而在众多的新型能源中,低温质子交换膜(PEM)燃料电池又以能量转换效率高、污染小、运行速度快等优点广泛应用于发电、汽车、便携设备等领域,成为了化石燃料的有力替代者。因此,如何提高燃料电池的性能来推动它的进一步发展成为了一个备受瞩目的课题。然而,目前商用的燃料电池阴极催化剂Pt/C的活性和耐久性很大程度上限制了燃料电池的发展。因为这种催化剂在反应过程中对中间产物的吸附能过高,降低了它的催化活性;在长期使用过程中不断发生粗化和剥落,影响了它的使用寿命。且贵金属Pt的成本和储量也制约了它的应用。因此,我们急需寻找一种价格低廉且催化活性高、稳定性好的新型催化剂来代替Pt/C催化剂来改善燃料电池的性能。近几年研究者们最常用的方法是合金化法,即向Pt中加入过渡族元素M,如Fe、Co、Ni等,制备成Pt-M/Pt二元合金来改善催化剂的性能。这种合金催化剂虽然具有比Pt/C更高的催化活性,但在酸性电解质中依然会发生扩散和溶解,从而大大降低了催化剂的稳定性。因此我们对这种二元合金进行了改进,先采用合金化法制备Pt-M-Al三元合金,再采用去合金化法使这种三元合金形成纳米多孔结构。这种纳米多孔结构所具有的禁闭效应、负曲率效应和双电荷电层交叠效应能够对电催化起到显著的促进作用。因此,本论文将围绕这种纳米多孔三元合金在氧还原反应中的催化性能展开研究,其主要的研究内容及结果如下:1、纳米多孔(Pt1-xFex)3Al/Pt金属间化合物的合成及其催化性质的研究大量的研究结果表明,Pt-Fe合金虽具有比Pt/C更高的催化活性,但催化稳定性不足。因此,我们采用两步制备法,先通过合金化的方法合成母合金Pt10Fe2Al88,再采用去合金化法合成纳米多孔(Pt1-xFex)3Al/Pt金属间化合物。这种金属间化合物具有三维互通的双模式孔结构,且具有优异的电催化性能。在0.9 V(相对于标准氢电极电位)的电位下,纳米多孔(Pt1-xFex)3Al/Pt金属间化合物的比活性和质量活性分别为3.97 m A cm Pt-2和1.94 A mgpt-1,分别是目前商用的Pt/C催化剂(0.39 m A cmPt-2和0.13A mgpt-1)的10.2倍和14.9倍。在长达40,000圈的循环过后,其半波电位(ΔE1/2)仅向左偏移15 m V,电化学活性面积(ECSA)仍剩余74%。这种优异的催化活性和稳定性来自于Fe和Al产生的压缩应变和配体效应。二者的相互作用使Pt原子的d带中心发生了显著下移,同时抑制了表面Pt原子的扩散和演变,保护了内部Fe和Al不被腐蚀,从而稳固了该催化剂的催化活性。这使得纳米多孔(Pt1-xFex)3Al/Pt金属间化合物成为了下一代燃料电池阴极催化剂的有力候选者。2、纳米多孔(Pt_(1-x)Co_x)_3Al/Pt金属间化合物的合成及其催化性质的研究基于上一个工作中我们对Pt-Fe合金体系改良后取得的成功,我们同样对Pt-Co合金进行了改进。采用同样的合金/去合金化法,我们制备了纳米多孔(Pt_(1-x)Co_x)_3Al/Pt金属间化合物,并对其进行了一系列的结构和性能的表征。结果表明,这种纳米多孔阴极催化剂在0.9 V(相对于标准氢电极电位)的半波电位(ΔE1/2)为0.931V,比活性为3.50 m A cmPt-2,质量活性为1.72 A mgpt-1,分别是商用Pt/C催化剂(0.39 m A cmPt-2和0.13 A mgpt-1)的9.0倍和13.2倍。在50,000圈的长时间循环过后,其半波电位仅向左偏移13 m V,电化学活性面积(ECSA)仍剩余65%,质量活性仍保留61%。由此可见,纳米多孔(Pt1-xCox)3Al金属间化合物同样也可以作为阴极催化剂使用于燃料电池中。更重要的是,上述结果表明,这种三元催化剂的设计理念和合成方法不仅适用于Pt-Fe体系,也同样适用于Pt-Co体系,在未来还可以向更多的合金体系发展,为阴极催化剂提供更多的可能。
[Abstract]:In the increasingly serious environmental pollution, fossil fuel shortage today, looking for a kind of large reserves, low cost, environmentally friendly new energy is the key to solve the problems of environment and energy. But in many new energy, low temperature proton exchange membrane fuel cell (PEM) and the energy conversion efficiency, low pollution. Fast is widely used in power generation, automotive, portable equipment and other fields, has become a powerful alternative to fossil fuels. Therefore, how to improve the performance of the fuel cell to promote the further development of it has become a high-profile topic. However, the current commercial Pt/C fuel cell cathode catalyst activity and durability largely restricted the development of fuel cell. Because of this kind of catalyst in the reaction process of adsorption of the intermediate products can be too high, reduce its activity; in the long-term use to process Coarsening and spalling, affect the service life of it. And the noble metal Pt and the cost of reserves is also restricted its application. Therefore, we are looking for a low price and high catalytic activity, good stability of the performance of a new catalyst instead of Pt/C catalyst to improve the fuel cell. In recent years, researchers most the commonly used method is the alloying method, adding M to Pt transition elements, such as Fe, Co, Ni, the performance of prepared Pt-M/Pt two yuan to improve the alloy catalyst. This alloy catalyst has higher catalytic activity than the Pt/C, but will still occur in acidic electrolyte diffusion and dissolution. Thus greatly reduce the stability of the catalyst. So we made improvement of the two yuan to three yuan alloy, preparation of Pt-M-Al alloys by alloying method, then the dealloy method makes the three element alloy forming nanoporous structure. The nano meter The confinement effect of pore structure with the negative curvature effect and electric double layer overlap effect to significant effect on Electrocatalytic. Therefore, this paper will focus on the three nanometer porous alloy has been studied in the catalytic performance of oxygen reduction reaction, the main research contents and results are as follows: 1. Nano porous (Pt1-xFex) on the synthesis and catalytic properties of a large number of research results of 3Al/Pt intermetallic compounds show that Pt-Fe alloy has higher catalytic activity than Pt/C, but the catalytic stability is insufficient. Therefore, we use two step preparation method, method by alloying synthesis of master alloy Pt10Fe2Al88, and then used to alloy the method of synthesis of nano porous 3Al/Pt intermetallic compound (Pt1-xFex) dual mode. The porous structure of the intermetallic compound has a three-dimensional interconnected, and has excellent electrocatalytic properties. In 0.9 V (relative to the standard hydrogen power Potential) potential, nano porous 3Al/Pt intermetallic compound (Pt1-xFex) specific activity and quality activity were 3.97 m and 1.94 A cm Pt-2 A mgpt-1, respectively, the current commercial Pt/C catalyst (0.39 m A cmPt-2 and 0.13A mgpt-1) 10.2 times and 14.9 times. After 40000 cycles and the half wave potential (E1/2) only left 15 m offset V, electrochemical active area (ECSA) still remaining 74%. the excellent catalytic activity and stability from the Fe and the Al compression strain and the ligand effect. The interaction between the two Pt atoms in the d band heart changed significantly down, at the same time inhibition of diffusion and evolution of surface Pt atoms, Fe and Al do not protect the internal corrosion, thus enhancing the catalytic activity of the catalyst. The nano porous 3Al/Pt intermetallic compound (Pt1-xFex) has become a strong candidate for the next generation of fuel cell cathode catalyst .2, nano porous (Pt_ (1-x) Co_x) on the synthesis and catalytic properties of _3Al/Pt intermetallic compounds on the basis of the previous work we made of Pt-Fe alloy modified system after the success, we also of Pt-Co alloy was improved. The alloying to the same alloy /, we prepared nano porous. Preparation of (Pt_ (1-x) Co_x) _3Al/Pt intermetallic compounds, and characterized the structure and properties of a series. The results show that the nano porous cathode catalyst at 0.9 V (relative to the standard hydrogen electrode potential) of the half wave potential (E1 /2) 0.931V, A cmPt-2 specific activity was 3.50 m the quality and activity of 1.72 A mgpt-1, respectively, is a commercial Pt/C catalyst (0.39 m and 0.13 A cmPt-2 A mgpt-1) 9 times and 13.2 times. After a long time 50000 cycles, the half wave potential only left 13 m offset V, electrochemical active area (ECSA) still remaining 65%, quality The activity remains so 61%. (Pt1-xCox), nano porous 3Al intermetallic compounds can also be used as cathode catalyst in fuel cells. More importantly, the results show that the design concept of this kind of three yuan catalyst and synthesis method is not only applicable to the Pt-Fe system, also applies to the Pt-Co system, but also in the future to develop more alloy system, provide more possibility for the cathode catalyst.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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