胺基分子辅助合成多孔贵金属纳米晶及其电催化性能

发布时间：2018-05-21 03:05

本文选题：燃料电池 + 胺基分子　；参考：《南京师范大学》2017年博士论文

【摘要】：多孔贵金属纳米材料具有较大的比表面积、特殊的微纳结构,从而拥有较高的电催化活性和稳定性。有机功能分子配位还原是制备形貌与结构可控的贵金属纳米材料的重要方法。由于胺基有机化合物配位能力较强,同时又易于调控(易受溶液pH、温度等因素影响),使之在特殊结构和形貌贵金属纳米材料的合成上有独特的应用。另外一方面,功能化胺基分子也影响贵金属纳米材料的表面电子状态、具有独特的空间位阻效应,从而影响着贵金属纳米材料的催化活性、稳定性和选择性。本论文主要探讨了尿素(Urea)、精氨酸(Arginine)以及聚烯丙基胺盐酸盐(PAH)三类典型的胺基分子在制备多孔贵金属纳米材料中的应用,探讨了不同性质胺基分子对贵金属纳米材料组成和结构的影响,在此基础上进一步研究了催化剂的结构和形貌对其电催化性能的影响。具体如下:1.以Urea-PdⅡ作为前驱体,通过控制反应条件,制备了多孔Pd纳米碗(Pd NBs)、Pd纳米笼(PdNCs)以及实心Pd纳米粒子(Pd-SNPs)。结果显示:尿的引入是中空多孔Pd纳米结构形成的关键,并且中空/多孔结构与尿素的分解速率密切相关。电化学研究表明,Pd的中空/多孔结构对甲醇的电催化氧化展现出更好的催化活性。Pd纳米碗和Pd纳米笼对甲醇氧化的质量活性分别是实心Pd纳米粒子的2.11倍和1.86倍。2.在Arginine-H20体系中,使用H2PtC16为反应前驱体制备了立方体状Pt纳米自组装体(Pt-CNAs)。该自组装体具有粗糙的表面结构与多孔结构,其形成主要归因于精氨酸中的胍基基团(多功能胺基)与羧基之间强烈的氢键或静电作用。电催化性能测试表明:在酸性甲醇电催化反应中,Pt-CNAs展现出了优越的电催化活性,其面积活性和质量活性分别是商业化Pt催化剂的2.73倍和2.40倍。同时它展现出良好的CO抗毒化性能和稳定性能。3.在前一章工作的基础上,利用精氨酸的自组装性质和配位能力制备了组成、结构可调控的枝状Pt-Cu纳米自组装体(PtCuDBNAs)。一方面,精氨酸分子之间强烈的氢键或静电作用促进初级纳米晶之间的自组装;另一方面,精氨酸分子与金属离子之间强的配位能力使Pt-Cu合金结构形成。与Pt1Cu3, PtiCui及商业化Pt催化剂相比,Pt3Cu1纳米自组装体显示了更优越的电催化活性和稳定性,这主要归因于Pt3Cu1纳米晶独特的枝状结构与双金属之间的协同效应。4.使用高分子胺化合物PAH作为结构导向剂和乙二醇(EG)作为溶剂,通过一步共还原法制备了表面具有多孔结构的荆棘状Au@Pd纳米催化剂(Au@Pd CSNTs)。通过不同条件控制实验证实Au@Pd CSNTs的形成是PAH和EG共同作用的结果。与商业化Pd催化剂相比,Au@PdCSNTs对氧气的电催化还原显示出更高的半波电位、动力学电流密度以及高的电催化稳定性,这归因于其独特的多孔结构和Au核与Pd壳之间的协同效应。5.高指数晶面的纳米晶含有高密度的台阶原子及扭结位原子,其配位数较少、化学活性高,很容易与反应物分子相互作用,使其成为催化活性中心。在本章节中,使用PAH作为结构导向剂合成了具有高指数晶面的三元PtAgCu@PtCu凹纳米八面体(CSCNOs)。形成机理研究表明AgⅠ和CuⅡ在预生成的Pt晶核上的催化还原生长导致了核壳纳米结构的形成。氧化刻蚀机理是最终凹纳米结构形貌形成的关键因素。由于其独特的几何效应、电子效应和双功能机制,所制备的PtAgCu@PtCu CSCNOs对甲酸的电催化氧化显示出了极好的电催化活性和稳定性,其面积活性(1.52 mAcm-2)分别是商业化Pt催化剂(0.16 mA cm-2)与PtCu纳米花(0.97 mA cm-2)的9.50倍和1.57倍。
[Abstract]:Porous noble metal nanomaterials have a large specific surface area and special micro nano structure, which have high electrocatalytic activity and stability. Organic functional molecular coordination reduction is an important method for the preparation of morphology and structure controlled noble metal nanomaterials. Because of the strong coordination ability of amido organic compounds, it is easy to regulate and control. The effects of pH, temperature and other factors on the synthesis of noble metal nanomaterials with special structures and morphologies have unique applications. On the other hand, functionalized amines also affect the surface electron state of noble metal nanomaterials, and have unique spatial steric effects, which affect the catalytic activity of noble metal nanomaterials and stabilize the catalytic activity of noble metal nanomaterials. In this paper, the application of three kinds of typical amino groups, urea (Urea), arginine (Arginine) and polyallyl amine hydrochloride (PAH), in the preparation of porous noble metal nanomaterials are discussed. The effects of different amino groups on the composition and structure of precious metal nanoscale materials are discussed. The effects of the structure and morphology of the catalyst on its electrocatalytic properties are as follows: 1. the porous Pd nano bowl (Pd NBs), Pd nanoscale cage (PdNCs) and solid Pd nanoparticles (Pd-SNPs) were prepared by controlling the reaction conditions. The results show that the introduction of urine is the key to the formation of hollow porous Pd nanostructures, and the hollow / hollow / hollow / porous structure is the key to the formation of a hollow porous Pd nanostructure. The porous structure is closely related to the decomposition rate of urea. The electrochemical study shows that the hollow / porous structure of Pd shows better catalytic activity for the electrocatalytic oxidation of methanol. The.Pd nano bowl and Pd nano cage are 2.11 times and 1.86 times.2. of the solid Pd nanoparticles respectively in the Arginine-H20 system, using H2PtC16 in the H2PtC16 system, respectively. The cubic Pt nano self assembly (Pt-CNAs) was prepared for the reaction precursor. The self assembled body has a rough surface structure and porous structure, which is mainly attributed to the strong hydrogen bond or electrostatic action between the guanidine group (polyfunctional amine group) and the carboxyl group in arginine. The electrocatalytic performance test shows that the electrocatalytic reaction of acid methanol is found. Pt-CNAs shows excellent electrocatalytic activity, its area activity and mass activity are 2.73 times and 2.40 times that of commercialized Pt catalysts. At the same time, it shows a good anti toxic and stable performance of CO, based on the work of the previous chapter, using the self-assembly properties and coordination ability of arginine, the structure is adjustable. Controlled dendritic Pt-Cu nanoself assembly (PtCuDBNAs). On the one hand, the strong hydrogen bond or electrostatic interaction between arginine molecules promotes self-assembly between the primary nanocrystals; on the other hand, the strong coordination between arginine and metal ions makes the Pt-Cu alloy structure. Compared with Pt1Cu3, PtiCui and commercialized Pt catalysts, Pt3Cu1 Na The rice self-assembly shows superior electrocatalytic activity and stability, which is mainly attributed to the synergistic effect between the unique branch structure of Pt3Cu1 nanocrystals and the bimetal..4. uses the high molecular amines compound PAH as the structural guide and ethylene glycol (EG) as a solvent. The spinous Au@Pd nano catalyst (Au@Pd CSNTs). Through the control experiments of different conditions, it is proved that the formation of Au@Pd CSNTs is the result of the joint action of PAH and EG. Compared with commercial Pd catalyst, Au@PdCSNTs has higher half wave potential, dynamic current density and high electrocatalytic stability. The special porous structure, the synergistic effect between the Au nucleus and the Pd shell, the nanocrystalline with high density of.5. surface with high density of step atoms and kink atoms, has less coordination number and high chemical activity. It is easy to interact with the molecules of the reactant and make it a catalytic activity center. In this chapter, PAH is used as a structural guide to synthesize the products. The formation mechanism of three PtAgCu@PtCu concave nanosheets (CSCNOs) with high exponential crystal surface (CSCNOs) shows that the catalytic reduction growth of Ag I and Cu II in the pre generated Pt nucleation leads to the formation of the nuclear shell nanostructures. The mechanism of the oxidation etching is the key factor for the formation of the final concave nanostructure. With the dual function mechanism, the prepared PtAgCu@PtCu CSCNOs shows excellent electrocatalytic activity and stability for the electrocatalytic oxidation of formic acid. Its area activity (1.52 mAcm-2) is 9.50 times and 1.57 times that of commercial Pt catalyst (0.16 mA cm-2) and PtCu nanoscale (0.97 mA cm-2).
【学位授予单位】：南京师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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