燃料电池催化剂用铂基纳米晶的可控制备及电催化性能研究

发布时间：2018-01-09 01:30

本文关键词：燃料电池催化剂用铂基纳米晶的可控制备及电催化性能研究　出处：《浙江大学》2017年博士论文　论文类型：学位论文

【摘要】：随着能源短缺和环境污染等问题日益严重,发展质子交换膜燃料电池,成为国际上重点鼓励和发展的新能源创新技术之一。燃料电池具有无污染、能量转换率高、能量密度大、体积小、重量轻等核心优势,在燃料电池汽车领域具有极大的应用前景。燃料电池汽车作为近年来新能源汽车发展的重要路线之一,制约其大规模商业化推广应用的因素之一在于其昂贵的铂(Pt)催化剂。同时,商用Pt催化剂在使用过程中还存在阴极氧还原反应动力学缓慢,阳极易被CO毒化及循环稳定性差等问题。本论文以研制低Pt负载、高催化性能的铂基金属纳米晶催化剂为目标,通过对其成分、结构和形貌的综合设计,探索铂基纳米晶催化剂的可控制备方法,改善催化性能。全文主要创新研究成果如下:(1)通过Rh作为亲氧金属且耐腐蚀的成分设计和高指数晶面外露的形貌设计,在油胺体系下,通过共还原三氟醋酸铑和乙酰丙酮铂,以十六烷基三甲基溴化铵(CTAB)为修饰剂,一步法合成了 RhPt合金纳米枝晶,并用于甲醇氧化催化反应(MOR)。CTAB的修饰作用是枝状结构形成的关键。枝晶表面有大量的(111)晶面、(311)高指数晶面及原子缺陷和台阶扭折,这些都是催化反应的高活性位点。Rh作为亲氧和耐腐蚀金属,与Pt进行复合,用于甲醇氧化(MOR)催化反应中,催化剂的抗CO中毒能力显著增强,活性和稳定性显著提高。Rh35Pt65比活性为3.33 mA/cm2,是商用Pt/C催化剂(0.38 mA/cm2)的8.8倍;质量活性为0.44mA/μgPt,是商用Pt/C催化剂的2.2倍。(2)通过原子尺度的核壳结构设计和基于核壳晶格应力效应、(111)外露晶面、及单晶和孪晶的几何设计,在油胺体系下,采用种子生长法,首次在热力学控制下实现了 Pt原子层在Pd核上的高质量层状外延生长,合成了超薄Pt层Pd@Pt核壳二十面体纳米晶,并用于氧还原催化反应(ORR)中。胺基小分子的吸附作用降低了 Pt的表面能,是实现Pt层状外延的关键。Pd@Pt核壳二十面体的ORR活性和稳定性获得显著提高,质量活性和比活性分别为3.49 mA/μgPt和3.02 mA/cm2Pt,分别是商用Pt/C催化剂的29倍和17.7倍;在30000个ADT循环后质量活性仅衰减了 23.6%。另外,本文首次通过几何相位分析法(GPA)定量分析了 Pd@Pt核壳二十面体和八面体纳米晶的应力分布状况,揭示了压缩应力分布和大小对ORR性能的影响。(3)在油胺体系下,通过在Pd八面体和立方体晶种上应力诱导的Stranski-Krastanov生长机制,合成了 Pd@Pt六足和Pd@Pt八足结构纳米晶。构建了一种可精确控制分枝数目的Pd@Pt枝状结构的普适性方法。由于Pd@Pt多足纳米枝晶的高指数外露晶面和双金属的协同作用,在MOR中表现出增强的催化性能。(4)基于Rh的引入可提高Pt基纳米晶催化剂稳定性的设计思想,在乙二醇体系下合成了成分可调的RhPd合金纳米晶。进一步,在油胺体系中,通过种子生长法,合成了超薄Pt层RbPd@Pt三元八面体纳米晶,并用于ORR中。RhPd1:2@Pt八面体纳米晶催化剂在经30000个ADT循环测试后,性能仅损失19.7%,与超薄Pt层Pd@Pt纳米晶相比,RhPd@Pt三元八面体纳米晶具有更好的循环稳定性。(5)提出动力学控制的方法,以乙二醇为溶剂,一步法实现了超低Pt含量RhPdPt八面体三元合金纳米晶的可控合成,简化了三元RhPdPt纳米晶的制备步骤。与商用的Pt/C相比,其ORR催化活性获得了显著的提高。(6)通过廉价Cu的引入可降低催化剂的成本,而超薄Pt层的结构设计可减少Pt的用量。同时,利用多金属间协同作用和高指数外露晶面的形貌设计可提高催化剂的性能。基于上述思想,我们提出以CuPd为种子,采用湿化学法,成功制备出CuPd@Pt核壳多角枝状结构,该枝状的形成主要源于Cu发生的欠电位沉积(UPD)和同时伴随的置换反应。Cu43Pd57@Pt在MOR中,质量活性和比活性分别为0.35mA/μgPt和0.63mA/cm2Pt,分别是商用Pt/C催化剂的1.66倍和1.75倍。催化剂的抗CO中毒能力显著增强。
[Abstract]:With the energy shortage and environmental pollution problems have become increasingly serious, the development of proton exchange membrane fuel cell, has become one of the new energy technology innovation international focus on encouraging and developing. The fuel cell has the advantages of no pollution, high energy conversion rate, high energy density, small volume, light weight and other core advantages, has great application prospect in fuel cell the automobile field. The fuel cell vehicle is one of the most important route for the development of new energy vehicles in recent years, one of the factors restricting the large-scale commercial application because of its expensive platinum (Pt) catalyst. At the same time, taking use of Pt catalyst in use still exist in the process of cathodic oxygen reduction reaction is slow, easy to be poisoned and anode CO poor cycling stability. This paper is to develop a low Pt load, Pt based metal nanocrystal catalysts with high catalytic performance as the goal, based on the composition, structure and morphology of the composite. Plan, explore the controllable preparation method of platinum based nanocrystalline catalyst, improve the catalytic performance. The main innovative results are as follows: (1) using Rh as the design of composition design and morphology of high index surfaces exposed oxophilic metal and corrosion resistance, in oil amine system, is also by original three fluorine acetic acid rhodium and acetylacetone platinum, with sixteen alkyl three methyl bromide (CTAB) as modifier, RhPt alloy Nanodendrites was synthesized by one-step method, and used for methanol oxidation reaction (MOR) modification of.CTAB is the key to the formation of dendritic structure. The dendrite surface has a large number of (111) crystal planes (311) high index surfaces and the atomic defects and step kink, these are.Rh high active site catalytic reactions as oxophilic and corrosion resistant metal with Pt composite for methanol oxidation (MOR) catalytic reaction and resistance to CO poisoning catalyst significantly enhanced the activity and stability significantly. The high activity of.Rh35Pt65 was 3.33 mA/cm2, is a commercial Pt/C catalyst (0.38 mA/cm2) 8.8 times; the quality of the activity for 0.44mA/ gPt, is 2.2 times that of commercial Pt/C catalyst. (2) the core-shell structure design of atomic scale and core-shell lattice based on stress effect, (111) the exposed surface, geometric design and single and twin crystal, in oil amine system, using the seed growth method, for the first time in the thermodynamic control achieves high quality epitaxial layered Pt atomic layer in the Pd nuclear growth of ultrathin Pt layer Pd@Pt core-shell synthesis twenty nanocrystals, and used for oxygen reduction reaction (ORR) adsorption. The role of amino small molecules reduces the surface energy of Pt, is the key to achieve Pt.Pd@Pt core-shell layered extension of the twenty face of ORR activity and stability were significantly increased, the quality of activity and specific activity were 3.49 mA/ gPt and 3.02 mA/cm2Pt, respectively, is 29 times of Pt/C catalyst and 1 7.7 times; in 30000 after the ADT cycle quality activity only decreased by 23.6%. in addition, for the first time through geometric phase analysis (GPA) quantitative analysis of the stress distribution of the core shell Pd@Pt twenty surface and eight surface nanocrystalline, reveals the effect of compression stress distribution and size on the performance of ORR (3.) in oil amine system, through the Pd eight surface and cube crystal on the stress induced growth mechanism of Stranski-Krastanov, Pd@Pt six and Pd@Pt eight foot foot structure nanocrystals were synthesized. To construct a precise control of branch number Pd@Pt branched universal method. Due to the synergistic effect of high exposure Pd@Pt multiped index crystal Nanodendrites and double metal, showed enhanced catalytic properties in MOR. (4) the introduction of Rh can improve the design idea of Pt based nanocrystalline catalysts based on stability in ethylene glycol system, the synthesis of RhPd alloy with adjustable sodium Nanocrystalline. Further, the oil amine system, through the seed growth method, synthesis of ultrathin Pt layer RbPd@Pt three yuan eight nanocrystals, and used ORR.RhPd1:2@Pt eight surface nanocrystalline catalyst in the 30000 ADT cycle test, the performance loss is only 19.7%, compared with the Pt thin layer of Pd@Pt nanoparticles. The cycle stability of RhPd@Pt three Yuan eight nanometer crystal has better. (5) proposed method of dynamic control, using ethylene glycol as solvent, controllable synthesis of one step to achieve the RhPdPt ultra low Pt content in eight face three element alloy nanocrystals, simplifies the preparation steps of three yuan compared with RhPdPt nanocrystals. The commercial Pt/C, the catalytic activity of ORR was significantly improved. (6) through the introduction of cheap Cu can reduce the cost of the catalyst, and the structure design of ultrathin Pt layer can reduce the dosage of Pt. At the same time, the synergism between metal and high index surface morphology can be exposed To improve the performance of the catalyst. Based on the above idea, we propose for the seeds to CuPd by wet chemical method, successfully prepared CuPd@Pt core-shell multi angle dendritic structure, the underpotential deposition of dendritic formation is mainly due to the occurrence of Cu (UPD) and.Cu43Pd57@Pt accompanied by the replacement reaction in MOR, the quality of activity and the specific activity were 0.35mA/ gPt and 0.63mA/cm2Pt, were 1.66 times and 1.75 times that of the commercial Pt/C catalyst. The catalyst significantly enhanced resistance to CO poisoning.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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