类普鲁士蓝基复合材料及贵金属掺杂改性材料的制备和应用研究

发布时间：2018-06-21 05:30

本文选题：配位聚合物 + 类普鲁士蓝粒子　；参考：《中国科学技术大学》2015年博士论文

【摘要】：类普鲁士蓝粒子是一类重要的配位聚合物,和其他配位聚合物一样,类普鲁士蓝粒子具有极大的比表面,很高的孔隙率,其孔径均匀可调等优点。由于在普鲁士蓝晶胞中,过渡金属离子占据两个不同的位置,而这两个位置上都可以用不同的其他过渡金属来替代,导致了类普鲁士蓝粒子极大的品种多样性。它们的性能各有优势,值得深入研究。在超级电容器电极制备领域,各种纳米复合材料、结构都有过尝试,特别是一维的碳纳米管和二维的石墨烯与过渡金属氧化物的复合结构,取得了很好的效果。但是就实际应用来看,这些电极材料的能量密度还是不够大,难以满足工业上日益增长的需求。本文中采用一种新的复合材料,使用多孔大比表面的类普鲁士蓝粒子作为基底,在外面形成金属氧化物外层,既能利用类普鲁士蓝粒子的大容量,又能结合金属氧化物的快速充放电性质,实现更好的电化学性能。本文探讨了这种复合材料的两种不同的结构,核壳结构和层状复合结构,各有优势,都能实现预期的性能结果。贵金属是最常用的具有极佳催化效果的催化剂。但是由于贵金属元素的稀有性,通常成本很高。将贵金属纳米化能够节省材料的用量,而且可以提高催化剂的活性。但是即使纳米颗粒的尺寸小到2nm,依然有一半左右的贵金属原子处于晶粒内部,不能接触到催化反应。最近的单原子催化剂提供了新的思路。基于类普鲁士蓝粒子的大比表面,我们将贵金属取代其中过渡金属元素,使得贵金属能够充分的与反应物接触,实现贵金属元素的最大利用率。基于以上思路,本论文的主要工作包括以下几个方面的内容： 1.我们通过非常简单的共沉淀法制备了一种铁氰酸锰与二氧化锰复合的核壳结构纳米粒子,并且尝试于用作电化学电容器的电极材料。随后,使用一种新的称作“过氧化法”的方法进一步完善我们的复合结构纳米粒子,这个过程中铁氰酸锰粒子中不稳定的二价锰成分变成了三价锰,同时还有部分锰元素迁移到了粒子外壳形成一层二氧化锰壳层。我们使用环境友好的硫酸钠溶液作为电解液来探测该粒子作为电化学电容器的性能,并且看到了非常有趣的实验现象,同时在5mV s-1的扫速下,1.3V的电势范围内,平均225.6F g-1的高容量能够重复实现。这样宽的电势区间使得我们的电极材料具有很高的能量密度,在0.5A g-1的电流密度条件下获得74.5Wh kg-1,这个值比大多数文献中报道的二氧化锰材料都要高,大幅提升了目前电容器材料的能量密度。DOME电极中活性物质的两种成分,MnHCF和Mn02对实现高容量和高能量密度都起到了关键的作用,这些都反映在了同时具有两种特性的CV曲线和充放电曲线中。而且,就像XPS谱反映的那样,在充放电过程中,MnHCF中的锰元素价态未发生变化,电极的电化学容量来源于MnO2中三价锰与四价锰之间的转变,以及MnHCF中二价铁与三价铁之间的转变。 2.我们设计了一种多级双层结构复合材料电极,由极薄二氧化锰片层包覆住NiHCF局域网状结构。这种新颖的多功能结构作为超级电容器正极材料同时具备了结构上和成分上的优化选择,结合了高能量密度的金属有机框架结构和高功率密度的赝电容材料二氧化锰,以及新发现的这种双层复合结构的ICE效应。作为超级电容器的正极材料,这种双层复合结构显示了高容量,高能量密度和高功率密度以及相当不错的循环稳定性。我们的制备方法简单而适用于多种此类双层复合结构。更重要的是,界面浓度效应(ICE效应)头一次被发现,为后来的电容器材料结构设计提供了很好的参考。 3.通过精细的实验和完整的分析,我们证明了一系列的贵金属,包括Pd、Pt、Ag和Au元素在水溶液中能够深入到金属铁氰化物前驱体中,并且成功的取代部分铁元素。这些贵金属掺杂的类普鲁士蓝粒子包括Pd-MnHCF、Pt-MnHCF、 Ag-MnHCF、Au-MnHCF、Pd-CoHCF、Pt-CoHCF、Ag-CoHCF、Au-CoHCF、 Pd-NiHCF、Pt-NiHCF、Ag-NiHCF和Au-NiHCF,它们的形貌以及基本尺寸依赖于前驱体的形貌和尺寸。这整个的过程在温和的水热环境中或者在室温下完成,而没有破坏原本可调的开放孔道结构。这种普鲁士蓝类配位聚合物和这一系列的贵金属不仅有很好的匹配性,而且通过控制反应条件能够实现对粒子尺寸,形貌以及结构的调控。贵金属元素丰富的多样性,它们在框架结构中均匀的分布以及高度可控的纳米结构无疑会实现在众多领域的良好表现,尤其是在单原子催化领域以及气体吸附领域。其中,我们已经证明了Pd-MnHCF是一种非常好的单原子催化剂,在对硝基苯酚的催化还原反应中具有独特的,效率极高的催化性能,以及在硼氢化钠溶液中很好的耐还原性,打破了一直以来在强还原性环境里只有零价贵金属纳米粒子作为催化剂的垄断现象。除了可以掺入上述一系列的贵金属元素,这种掺杂方法还适用于掺杂一系列的稀土元素,这些元素可能会在MRI中的T1和T2成像有很好的效果。
[Abstract]:The Prussian blue particles are an important class of coordination polymers. Like other coordination polymers, the Prussian blue particles have the advantages of great specific surface, high porosity and uniform pore size. Because of the two different positions of transition metal ions in the Prussian blue crystal cell, the two positions can be used differently. The substitution of other transition metals leads to a great variety of Prussian blue particles. Their properties have advantages and are worthy of further study. In the field of supercapacitor electrode preparation, various nanocomposites and structures have been tried, especially one dimensional carbon nanometers and two dimensional graphene and transition metal oxides. In the actual application, the energy density of these electrodes is still not large enough to meet the growing demand in industry. In this paper, a new composite material, using a porous Prussian blue particle with a porous surface as the base, is used to form a metal oxide outer layer. Using the large capacity of Prussian blue particles and the rapid charging and discharging properties of metal oxides, a better electrochemical performance is achieved. This paper discusses two different structures of the composite, the core and the shell structure and the layered composite structure, each of which has advantages.
Precious metals are the most commonly used catalysts with excellent catalytic effects. But because of the rarity of precious metals, the cost is very high. Nanocrystallization of precious metals can save the amount of material and improve the activity of the catalyst. But even if the size of the nanoparticles is small to 2nm, about half of the precious metals are in the crystal. The recent single atom catalyst provides a new way of thinking. Based on the larger surface of the Prussian blue particles, we replace the transition metal elements with precious metals so that the precious metals can be fully exposed to the reactants to achieve the maximum utilization of precious metals.
Based on the above ideas, the main work of this paper includes the following aspects:
1. by a very simple coprecipitation method, we have prepared a kind of nuclear shell structure nanoparticles composed of manganese ferricyanate and manganese dioxide, and tried to be used as the electrode material of the electrochemical capacitor. Then, a new method called "peroxide method" was used to further improve our composite structure nanoparticles. The unstable two valent manganese component in the manganese cyanate particle turns into a trivalent manganese, while some manganese elements are migrated to the shell to form a layer of manganese dioxide. We use environmentally friendly sodium sulfate solutions as the electrolyte to detect the particle as an electrochemical capacitor, and see very interesting experimental phenomena. At the same time at the speed of 5mV s-1, the high capacity of the average 225.6F g-1 can be repeated within the range of the potential of 1.3V. This wide potential range makes our electrode material have a high energy density and obtain 74.5Wh kg-1 under the current density of 0.5A g-1, which is higher than most of the manganese dioxide reported in most of the literature. Two components of the active substance in the energy density.DOME electrode of the current capacitor are greatly enhanced. MnHCF and Mn02 play a key role in achieving high capacity and high energy density. These are reflected in the CV curves and charge discharge curves with two characteristics at the same time. And, as reflected in the XPS spectrum, it is charged and discharged. In the process of manganese valence of MnHCF did not change, the change of source electrode electrochemical capacity between MnO2 trivalent manganese and tetravalent manganese, and the transformation between MnHCF two valent iron and ferric iron.
2. we designed a multilevel double layer composite electrode, which is coated with an extremely thin layer of manganese dioxide in a NiHCF LAN like structure. This novel multi-functional structure, as a supercapacitor positive material, has both structural and composition optimization, combined with high energy density metal organic frame structure and high power. Density pseudo capacitive material manganese dioxide, and the newly discovered ICE effect of this double layer composite structure. As a cathode material for supercapacitors, this double layer composite structure shows high capacity, high energy density, high power density, and quite good cyclic stability. Our preparation method is simple and suitable for a variety of double layers. More importantly, the interface concentration effect (ICE effect) is first discovered, providing a good reference for the later design of capacitor material structure.
3. through fine experiments and complete analysis, we have demonstrated that a series of precious metals, including Pd, Pt, Ag and Au, can penetrate into the metal ferricyanide precursor in aqueous solution and succeed in replacing some of the iron elements. These noble metal doped Prussian blue particles include Pd-MnHCF, Pt-MnHCF, Ag-MnHCF, Au-MnHCF, Pd-CoHCF, Pt-CoHCF, Ag-CoHCF, Au-CoHCF, Pd-NiHCF, Pt-NiHCF, Ag-NiHCF and Au-NiHCF, their morphology and basic dimensions depend on the morphology and size of the precursors. The whole process is completed in a mild hydrothermal environment or at room temperature without destroying the original adjustable open channel structure. This Prussian blue coordination polymer and this A series of precious metals not only have good matching, but also control the size, morphology and structure of particles by controlling the reaction conditions. The rich diversity of precious metals, their uniform distribution in the frame structure and highly controllable nanostructures will undoubtedly achieve good performance in many fields, especially in the field. In the field of Single Atom Catalysis and the field of gas adsorption, we have shown that Pd-MnHCF is a very good single atom catalyst, which has a unique, highly efficient catalytic performance in the catalytic reduction reaction of p-nitrophenol and a good reducibility in the sodium borohydride solution, breaking the strong reducibility ring. Exit only zero valent metal nanoparticles as catalyst. In addition to monopoly phenomenon can be incorporated into a series of noble metal elements, this doping method is also applicable to a series of doped with rare earth elements, these elements may be T1 and T2 imaging in the MRI have very good results.
【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】：2015
【分类号】：TB332;TM53

【共引文献】