铂基纳米结构的控制制备及其电催化性能研究

发布时间：2018-05-27 04:48

本文选题：铂基纳米材料 + 热分解　；参考：《中国科学技术大学》2017年博士论文

【摘要】：随着化石燃料的快速消耗,由此而产生的环境问题和能源危机日益严峻,人们正致力于绿色、清洁能源技术的开发。电解水制氢和燃料电池因其各自的优点被认为是非常有潜力的新能源技术。铂(Pt)因其优异的电催化性能被广泛地用作以上两类反应的催化剂。然而,其储量较低、价格昂贵以及催化过程中的活性因中毒退化和稳定性问题一直成为制约Pt基催化剂发展的瓶颈所在。本论文从Pt基贵金属单分散纳米晶的可控生长条件及纳米晶成核、生长热力学和动力学出发,开展单分散Pt基纳米晶催化剂的合成方法及其控制制备研究,探讨和分析其在电解水产氢和燃料电池阳极反应中的催化活性和稳定性提高及机理等问题。具体研究结果和创新点如下:1.发展了一种简单的寡铂纳米晶催化剂制备方法,利用热解新型配位聚合物控制制备出高活性和高稳定性的三维(3D)Pt/C复合电催化剂。具体利用温和的溶剂热方法,以氯铂酸为铂源和4-硝基苯酚为配体合成了由Pt(Ⅱ)有机配位聚合物和微小Pt纳米颗粒组成的均匀球形前驱体。利用Ar/H2气氛退火,将其转化为3D Pt/C复合材料,退火后的材料尺寸相对于退火前减少了 30%。研究发现,该复合材料是由直径～4.5 nm单分散的Pt纳米颗粒和均匀分布的氮掺杂多孔碳组成,其中氮含量为2.89 at%,主要为吡啶氮、吡咯氮、石墨氮和氧化的氮。为了研究氮掺杂多孔碳碳对电催化性能的影响,我们选择商业化Pt黑催化剂作为对比,研究了所制备的3D Pt/C复合催化剂电催化乙二醇氧化反应(EGOR)、甲醇氧化反应(MOR)和乙醇氧化反应(EOR)的催化活性和稳定性。该设计策略有望进一步拓展用于制备其他碳负载双金属/多金属复合材料。2.发展了 NiPt纳米线的制备方法。通过设计温和的溶剂热合成路线,成功制备出一维(1D)海参状NiPt固溶相纳米线,并且我们对纳米线的自组装机理进行了深入探究。研究结果表明,乙二胺分子强烈地吸附在纳米线的表面并增强一维纳米结构的各向异性生长,海参状的合金纳米线正是在溶液热力学与晶体热力学共同调控下,由大量颗粒状亚单元在乙二胺分子的辅助作用下自组装而形成。此外,此类催化剂是第一次被报道用于电催化析氧反应(OER),且表现出良好的催化活性和稳定性。对于典型的Ni、Pt原子比为23.6:1的NiPt催化剂而言,在较小的过电位0.396 V时,电流密度即可达到10 mA/cm2、Tafel斜率为55 mV/decade,且显示出良好的电化学催化稳定性。研究表明,其电催化性能的提高归因于贵金属Pt掺杂导致的NiPt催化剂表面粗糙结构的形成以及电荷转移能力的增强。3.基于金属之间氧化还原电位的差异,在热液条件下,通过简便的电化学置换反应控制制备出单分散CuPdPt固溶相纳米晶体。研究表明,Cu和Pd均匀分布于CuPdPt纳米晶中,而Pt主要分布于其外表面。由于Pt、Pd和Cu之间的协同效应,固溶相CuPdPt纳米晶的稳定性得到增强,且单分散纳米晶和载体之间的相互作用和电荷传导也得到增强,CuPdPt/C复合催化剂在电催化析氢反应(HER)中,表现出优异的电催化活性和稳定性。在-0.1 V(相对于可逆氢电极)下,与商业化Pt/C(60 wt%Pt)催化剂相比,CuPdPt/C催化剂的质量比活性提高了 701倍,其Tafel斜率为25 mV/decade,并且在经过20000次循环后,催化活性几乎不损失。更重要的是,复合催化剂中的Pt含量仅为0.095 wt%。4.发展了一种简易制备Pt基固溶相双金属纳米晶的普适方法。在OAm、ODE体系中,以相应的乙酰丙酮类化合物为前驱源,实现了 Pt-M(M = Ru、Ni、Co、Cu、Zn、Mn)超细蠕虫状纳米线的制备。着重研究和探索直径为～1.8nm的超细PtRu纳米线的控制制备、形成机理和电催化性能。ICP表明,Pt、Ru的原子比为110.6:1,HRTEM图像、HADDF-STEM图像和元素面分布图像显示,Pt均匀的分布在一维蠕虫纳米线中,而Ru零散地分布在于其中,该纳米线表面含有大量的缺陷,如晶界、拐角、扭结等缺陷结构。电化学结果表明,与商业化Pt/C(60 wt%Pt)催化剂相比,所制备的PtRu/C催化剂在电催化EGOR中,表现出更为优异的催化活性和稳定性。超细蠕虫状纳米线独特的表面结构、双金属电子结构的修饰、活性组分与Ketjen碳载体之间的强相互作用;而通过掺杂痕量的金属Ru,可以有效消除催化剂表面吸附的CO类有毒中间体,释放Ru邻近Pt的活性位点,提高所制备催化剂的抗CO毒化能力和稳定性能。
[Abstract]:With the rapid consumption of fossil fuels, the resulting environmental and energy crises are becoming increasingly severe. People are working on the development of green and clean energy technologies. Electrolytic hydrogen production and fuel cells are considered to be very potential new energy technologies because of their respective advantages. Platinum (Pt) is widely used because of its excellent electrocatalytic performance. The catalysts of the above two types of reactions, however, are low in reserves, high in price, and in the degradation and stability of catalytic activity due to toxic degradation and stability. In this paper, the controlled growth conditions and nanocrystalline nucleation, growth thermodynamics and kinetics of the Pt based monodisperse nanocrystalline crystals are derived. The synthesis method and control preparation of monodisperse Pt nanomi crystal catalyst are carried out. The catalytic activity and stability improvement and mechanism in the electrolysis of aquatic hydrogen and fuel cell anode reaction are discussed and analyzed. The specific research results and innovation points are as follows: 1. a simple method of preparation of oligomeric platinum nanocrystalline catalyst is developed. A three dimensional (3D) Pt/C composite electrocatalyst with high activity and high stability was prepared by a new coordination polymer of pyrolysis. A homogeneous spherical precursor composed of Pt (II) organic coordination polymer and micro Pt nanoparticles was synthesized by a mild solvothermal method, using chlorosulplatic acid as the platinum source and 4- nitrophenol as ligands. The use of Ar/H2 The atmosphere is annealed and transformed into 3D Pt/C composite. The annealed material size is reduced by 30%. research before annealing. The composite is composed of Pt nanoparticles with a diameter of 4.5 nm and a homogeneous distribution of nitrogen doped porous carbon. The nitrogen content is 2.89 at%, mainly pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and oxidation. In order to study the effect of nitrogen doped porous carbon and carbon on the electrocatalytic performance, we chose commercialized Pt black catalyst as a contrast to study the catalytic activity and stability of the prepared 3D Pt/C composite catalyst for electrocatalytic ethylene glycol oxidation (EGOR), methanol oxidation (MOR) and ethanol oxidation (EOR). This design strategy is expected to advance. The preparation of NiPt nanowires was developed for the preparation of other carbon loaded bimetallic / polymetallic composite materials.2.. By designing a mild solvent thermal bonding route, one dimensional (1D) sea cucumber NiPt solid solution nanowires were prepared successfully. And we explored the self-assembly mechanism of the nanowires. The results show that B two Amine molecules strongly adsorb on the surface of the nanowires and enhance the anisotropic growth of the one-dimensional nanostructures. The sea cucumber nanowires are formed by the assembly of a large number of granular subunits under the auxiliary action of ethylenediamine molecules under the co regulation of solution thermodynamics and crystal thermodynamics. In addition, the catalyst is the first time to be used. The report is used for the electrocatalytic oxygen evolution reaction (OER) with good catalytic activity and stability. For the typical Ni, the Pt atom is compared to the NiPt catalyst of 23.6:1, when the smaller overpotential is 0.396 V, the current density can reach 10 mA/cm2 and the Tafel slope is 55 mV/decade, and the good electrochemical catalytic stability is shown. The study shows that The improvement of the electrocatalytic properties is attributed to the formation of the surface roughness structure of the NiPt catalyst resulting from the Pt doping of precious metals and the enhancement of the charge transfer capacity of.3. based on the difference of the redox potential between metals. In the hydrothermal condition, the monodisperse CuPdPt solid solution nanocrystals were prepared by a simple electrochemical replacement reaction. It is shown that Cu and Pd are distributed uniformly in the CuPdPt nanocrystals, while Pt is mainly distributed on the outer surface. The stability of the solid solution CuPdPt nanocrystals is enhanced due to the synergistic effect of Pt, Pd and Cu, and the interaction between the monodisperse nanocrystalline and the carrier and the charge conduction are also enhanced, and the CuPdPt/C composite catalyst is in the electrocatalytic hydrogen evolution reaction (H). ER) showed excellent electrocatalytic activity and stability. Under -0.1 V (relative to reversible hydrogen electrode), the mass of CuPdPt/C catalyst was 701 times higher than that of commercial Pt/C (60 wt%Pt) catalyst, and its Tafel slope was 25 mV/decade, and the catalytic activity was almost no loss after 20000 cycles. The Pt content in the catalyst is only 0.095 wt%.4. to develop a simple method for the preparation of Pt based solid solution bimetallic nanocrystals. In the OAm, ODE system, the preparation of Pt-M (M = Ru, Ni, Co, Cu, Zn, and Zn) is prepared by using the corresponding acetacetone as the precursor, and the diameter is studied and explored. The preparation, formation mechanism and Electrocatalytic Performance.ICP of ultrafine PtRu nanowires show that the atomic ratio of Pt and Ru is 110.6:1, HRTEM images, HADDF-STEM images and element distribution images, and Pt is distributed uniformly in one-dimensional worm nanowires, and Ru scattered in the nanowires. The surface of the nanowire contains a large number of defects, such as grain boundary and corner, The electrochemical results show that, compared with the commercialized Pt/C (60 wt%Pt) catalysts, the prepared PtRu/C catalysts exhibit more excellent catalytic activity and stability in the electrocatalytic EGOR. The unique surface structure of the superfine vermicular nanowires, the modification of the bimetallic electronic structure, the active components and the Ketjen carbon carrier. Strong interaction can be achieved by doping trace metal Ru, which can effectively eliminate the CO toxic intermediate adsorbed on the surface of the catalyst, release the active site of Ru adjacent to Pt, and improve the CO toxicity and stability of the catalyst.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36

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