负载型金属纳米颗粒的光化学沉积可控合成及催化应用
发布时间：2018-07-29 07:45
【摘要】：随着纳米化学的发展,金属纳米颗粒受到越来越多的关注。特别是负载在多孔材料中的多金属纳米材料,在工业催化方面有很大的发展前景。但在其实际应用中,纳米颗粒的组成调控和热稳定性是困扰研究者的两大难题。很多合成方法无法对单个多金属颗粒的组成和尺寸进行精确调控,并且在后续的热处理过程中容易出现相分离和烧结等现象。针对上述情况,本文提出了简单和普适的原位光化学沉积合成策略,制备一系列负载型金属纳米颗粒。该方法采用多种金属前驱体的一步共同光沉积,在介孔限域空间内制备高分散、高活性和高热稳定性的多金属纳米颗粒。一方面,通过调控金属前驱体的浓度,可精确控制单个纳米颗粒的组成。另一方面,通过焙烧下的金属合金化过程,可制得小尺寸、抗烧结的均一合金纳米颗粒。我们考察了多金属纳米颗粒在光催化产氢、高温催化氧化等方面的应用,并在纳米合金相图的研究中得到了初步结果。主要研究内容如下：1)基于原位光化学沉积法,在介孔Ti02中均匀负载Cu纳米颗粒。考察Cu前驱体浓度和颗粒尺寸的关系。以甲醛溶液紫外光下的重整产氢作为探针反应,考察Cu-Ti02在光催化中的催化效果和作用机理。我们的研究表明低浓度的Cu前驱体可得到小尺寸的Cu纳米颗粒,更有利于光催化的进行。2)以三维笼状超大介孔TiO2为载体,采用光沉积法合成负载型Au/Pt/Pd单金属纳米颗粒。通过调控焙烧温度,考察Pt纳米颗粒的尺寸与温度的关系。另外,通过调控金属前驱体浓度,考察金属负载量和正己烷催化燃烧性能的关系。我们发现笼状介孔孔道的超大比表面积和有序限域结构有效增强了纳米颗粒的热稳定性,继而提高其催化性能。3)根据一步光合成的策略,将多种金属前驱体共同沉积到超大介孔YiO2的笼状孔道内,制得负载型双金属纳米颗粒(AuPt/AuPd/PtPd)。以AuPt为例,考察了低温焙烧下纳米颗粒的尺寸、组成和结构变化。AuPt颗粒高度分散在介孔孔道中,并在空气焙烧下由核壳结构变为单相合金结构。由于多金属间的协同作用,AuPt合金具有更好的催化燃烧性能。4)深入研究AuPtPd三金属纳米颗粒,考察其在高温空气焙烧下的尺寸、组成和结构变化。得益于原位共沉积过程,我们能够精确调控单个纳米颗粒中三种组分的含量。更重要的是,AuPtPd三金属体系具有超高温稳定性和抗氧化性。与单金属和双金属相比,三金属纳米颗粒在高温(700-900。C)焙烧下具有均匀的合金结构,并保持很高的金属Pd比例。纳米颗粒的三金属组成和介孔载体的限域空间对于其上述性质起到了关键作用。在正己烷催化燃烧反应中,AuPtPd催化剂也表现出稳定的催化性能。5)以AuPtPd体系为例,研究三金属材料的高温纳米合金相图。从实验数据的角度,展现纳米颗粒在800℃下的相变过程。对于不同组成的AuPtPd纳米颗粒,其XRD峰位置、峰型以及EDS所得的元素分布均有不同。我们首次绘制出AuPtPd纳米材料在800℃下的不混溶区等温线,并发现纳米尺度的合金相图不仅与尺寸效应有关,还受到组成效应的影响。通过相图中不同组成样品的正己烷催化燃烧性能,初步考察了纳米相图对于催化的指导作用。
[Abstract]:With the development of nanosochemistry, metal nanoparticles have attracted more and more attention. Especially the multi metal nanomaterials loaded in porous materials have great prospects in industrial catalysis. But in their practical applications, the composition and regulation and thermal stability of nanoparticles are the two difficult problems that perplex researchers. The composition and size of single polymetallic particles can not be regulated accurately, and phase separation and sintering are easy to occur during the subsequent heat treatment. In this paper, a simple and universal in situ photochemical deposition strategy is proposed to prepare a series of negative metal nanoparticles. This method uses a variety of metals. One step of the precursor's common photo deposition is to prepare polymetallic nanoparticles with high dispersion, high activity and high thermal stability in the mesoporous limit space. On the one hand, the composition of single nanoparticles can be controlled accurately by controlling the concentration of metal precursors. On the other hand, small size and anti sintering can be made by the metal alloying process under calcination. We investigated the application of polymetallic nanoparticles in the photocatalytic hydrogen production and high temperature catalytic oxidation and obtained the preliminary results in the study of the nanoscale phase diagram. The main contents are as follows: 1) Cu nanoparticles were uniformly loaded in mesoporous Ti02 based on in situ photochemical deposition. The precursor of Cu was investigated. The relationship between concentration and particle size. The catalytic effect and mechanism of Cu-Ti02 in photocatalytic catalysis are investigated by reformed hydrogen production under Formaldehyde Solution ultraviolet light as a probe. Our research shows that low concentration of Cu precursor can obtain small size Cu nanoparticles, and is more conducive to the photochemical.2) with three-dimensional cage like mesoporous TiO2 Supported Au/Pt/Pd single metal nanoparticles were synthesized by light deposition. The relationship between the size of Pt nanoparticles and the temperature was investigated by controlling the calcination temperature. In addition, the relationship between the metal load and the catalytic combustion performance of n-hexane was investigated by regulating the concentration of metal precursors. The ordered domain structure effectively enhanced the thermal stability of the nanoparticles and improved its catalytic performance.3). Based on the one step light synthesis strategy, a variety of metal precursors were deposited into the cage like channel of the super large mesoporous YiO2, and the AuPt/AuPd/ PtPd was prepared. The AuPt was used as an example to investigate the nanoscale particles under low temperature. The size, composition and structure change of.AuPt particles are highly dispersed in the mesoporous channel, and the core shell structure becomes single-phase alloy structure under the air roasting. Because of the synergistic effect of multi metal, AuPt alloy has better catalytic combustion performance.4) to study AuPtPd three metal nanoparticles and investigate its size under high temperature air roasting. The composition and structure change. Thanks to the in-situ co deposition process, we can accurately regulate the content of three components in a single nanoparticle. More importantly, the AuPtPd three metal system has super high temperature stability and oxidation resistance. Compared with the single metal and bimetallic, three metal nanoparticles have a uniform alloy under high temperature (700-900.C) roasting. Structure, and maintain a high proportion of metal Pd. The three metal composition of the nanoparticles and the confinement space of the mesoporous carrier play a key role in the above properties. In the catalytic combustion reaction of n-hexane, the AuPtPd catalyst also shows a stable catalytic performance.5), as an example of the AuPtPd system, to study the high temperature nanoscale phase diagram of the metal material. From the angle of experimental data, the phase transition process of nano particles at 800 C is shown. For different AuPtPd nanoparticles, the XRD peak position, peak type and EDS distribution are different. We first draw the isotherm of the immiscible region at 800 C at 800 C, and find that the nanoscale alloy phase diagram is not only the same as that of the nanoscale. The effect of the size effect is also influenced by the composition effect. Through the catalytic combustion performance of n-hexane of different composition samples in the phase diagram, the guiding role of nano phase diagram to catalysis is preliminarily investigated.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;O643.36
[Abstract]:With the development of nanosochemistry, metal nanoparticles have attracted more and more attention. Especially the multi metal nanomaterials loaded in porous materials have great prospects in industrial catalysis. But in their practical applications, the composition and regulation and thermal stability of nanoparticles are the two difficult problems that perplex researchers. The composition and size of single polymetallic particles can not be regulated accurately, and phase separation and sintering are easy to occur during the subsequent heat treatment. In this paper, a simple and universal in situ photochemical deposition strategy is proposed to prepare a series of negative metal nanoparticles. This method uses a variety of metals. One step of the precursor's common photo deposition is to prepare polymetallic nanoparticles with high dispersion, high activity and high thermal stability in the mesoporous limit space. On the one hand, the composition of single nanoparticles can be controlled accurately by controlling the concentration of metal precursors. On the other hand, small size and anti sintering can be made by the metal alloying process under calcination. We investigated the application of polymetallic nanoparticles in the photocatalytic hydrogen production and high temperature catalytic oxidation and obtained the preliminary results in the study of the nanoscale phase diagram. The main contents are as follows: 1) Cu nanoparticles were uniformly loaded in mesoporous Ti02 based on in situ photochemical deposition. The precursor of Cu was investigated. The relationship between concentration and particle size. The catalytic effect and mechanism of Cu-Ti02 in photocatalytic catalysis are investigated by reformed hydrogen production under Formaldehyde Solution ultraviolet light as a probe. Our research shows that low concentration of Cu precursor can obtain small size Cu nanoparticles, and is more conducive to the photochemical.2) with three-dimensional cage like mesoporous TiO2 Supported Au/Pt/Pd single metal nanoparticles were synthesized by light deposition. The relationship between the size of Pt nanoparticles and the temperature was investigated by controlling the calcination temperature. In addition, the relationship between the metal load and the catalytic combustion performance of n-hexane was investigated by regulating the concentration of metal precursors. The ordered domain structure effectively enhanced the thermal stability of the nanoparticles and improved its catalytic performance.3). Based on the one step light synthesis strategy, a variety of metal precursors were deposited into the cage like channel of the super large mesoporous YiO2, and the AuPt/AuPd/ PtPd was prepared. The AuPt was used as an example to investigate the nanoscale particles under low temperature. The size, composition and structure change of.AuPt particles are highly dispersed in the mesoporous channel, and the core shell structure becomes single-phase alloy structure under the air roasting. Because of the synergistic effect of multi metal, AuPt alloy has better catalytic combustion performance.4) to study AuPtPd three metal nanoparticles and investigate its size under high temperature air roasting. The composition and structure change. Thanks to the in-situ co deposition process, we can accurately regulate the content of three components in a single nanoparticle. More importantly, the AuPtPd three metal system has super high temperature stability and oxidation resistance. Compared with the single metal and bimetallic, three metal nanoparticles have a uniform alloy under high temperature (700-900.C) roasting. Structure, and maintain a high proportion of metal Pd. The three metal composition of the nanoparticles and the confinement space of the mesoporous carrier play a key role in the above properties. In the catalytic combustion reaction of n-hexane, the AuPtPd catalyst also shows a stable catalytic performance.5), as an example of the AuPtPd system, to study the high temperature nanoscale phase diagram of the metal material. From the angle of experimental data, the phase transition process of nano particles at 800 C is shown. For different AuPtPd nanoparticles, the XRD peak position, peak type and EDS distribution are different. We first draw the isotherm of the immiscible region at 800 C at 800 C, and find that the nanoscale alloy phase diagram is not only the same as that of the nanoscale. The effect of the size effect is also influenced by the composition effect. Through the catalytic combustion performance of n-hexane of different composition samples in the phase diagram, the guiding role of nano phase diagram to catalysis is preliminarily investigated.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;O643.36
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