层状结构复合材料的制备及其能量转换与储存性能研究

发布时间：2018-04-20 22:16

本文选题：层状材料 + 能量转换与储存　；参考：《上海电力学院》2017年硕士论文

【摘要】：随着社会的进步和发展,能源的消耗也是随之增多,并且伴随产生的环境污染问题也是越来越突出。因此为了满足人类的生产和生活需求,需要开发新型的清洁能源,而这种新能源还必须是可再生以及环保型。其中,光催化产氢,锂离子电池以及超级电容器是解决上述问题比较重要的三种能量转换的途径。光催化产氢是将太阳能转化成清洁环保的氢气的一种重要途径,不仅可以缓解日渐严重的能源危机还可以解决环境污染;而锂离子电池因具有长循环寿命、高能量密度以及环境友好型等优点,作为一种高效的能量储存和转换装置已开始广泛地应用在便携式电子设备和电动汽车上;而超级电容器作为另外一种高效的安全的清洁的能量储存和转换装置,因具有高功率密度、长寿命以及快速充放电等优点而引起了研究者的巨大关注。基于此,为了满足能量转换的发展需求,需要设计新型的电极材料和光催化剂。本文旨在通过对制约光催化剂和电极材料性能的因素的分析,设计和发展适用于光催化产氢、锂离子电池以及超级电容器的新型层状结构复合材料,以期实现提高层状结构复合材料在能量储存和转换中的应用。本论文的主要内容包括以下内容:(1)g-C_3N_4因其有着诸多优点如价格低廉、不含金属成分、稳定以及高效的光催化活性而受到了广泛的研究。而传统的体相的g-C_3N_4不仅比表面积小、光电复合效率高而且光催化产氢的效率也较低,这严重限制了g-C_3N_4在光催化产氢方面的应用。基于此,作者通过高温裂解三聚氰胺获得体相g-C_3N_4,再经过酸处理以及液相剥离得到了分散的g-C_3N_4纳米片,最后再辅以Photo-Fenton reaction获得了一种比表面积高达348 m~2 g~(-1)的边缘氧掺杂的层状多孔g-C_3N_4(HS g-C_3N_4-O)。通过计算发现HS g-C_3N_4-O的带隙值仅为2.434 e V,该值远低于体相g-C_3N_4的2.7e V,这可能是因为氧原子比氮原子多了一个电子,可以代替氮原子提供额外的电子,此外说明HS g-C_3N_4-O有着更好的传输特性以及可以更多的可见光捕获能力,有效地降低了光生电子和空穴的复合以及提高了光催化产氢率。HS g-C_3N_4-O的产氢率达到了202.56 umol h-1,远高于体相g-C_3N_4(70.65 umol h-1)和g-C_3N_4纳米片(122.56 umol h-1)。(2)基于对赝电容电极材料的导电性以及双电层电容电极材料的低容量的理解,作者首次导向性地合成了利用金属有机框架化合物MOFs转化而来的碳材料与聚苯胺(PANI)三明治结构的杂化材料,并将其应用于超级电容器测试,发现其具有很好的电化学性能。金属有机框架化合物(MOFs)是由有机配体与金属或者金属离子通过自组装形成的一类新型的多孔材料。近几年,由MOFs作为模板或者前驱体得到碳材料,已经逐渐地引起了人们的研究兴趣。此外聚苯胺(PANI)作为一种赝电容材料,因具有原料易得以及合成简便等优点而被认为是一种极具发展力的赝电容超级电容器电极材料。本文采用8-羟基喹啉作为有机配体和金属离子Zn~(2+)自组装形成MOFs作为前驱体,而后经过高温煅烧形成碳材料,再通过原位聚合的方式与聚苯胺复合,形成一种新型的三明治杂化材料。在电力密度为1A g~(-1)时,其比电容达到了477 F g~(-1)。经过100次的充放循环,其比电容仅仅损失了10%不到,说明该材料具有很好的循环稳定性。所表现出的优异的电化学性能,可能是因为三明治结构有效地缓解了循环过程中的体积膨胀以及电极的极化,其次碳材料可有效地提高复合材料的导电性,而具有赝电容性质的聚苯胺可以提高复合材料的容量。(3)传统的锂离子电池所使用的的负极材料为石墨,而石墨的理论储锂容量仅为372 m Ah g~(-1),这严重限制了锂离子电池在下一代电气设备上的应用。为此,需要设计出一种新型的高容量的锂离子电池负极材料。而在众多的负极材料中,具有二维层状结构的二硫化钼(MoS_2)因其理论容量为670 m Ah g~(-1)而受到研究者的广泛关注。二硫化钼(MoS_2)具有与石墨烯类似的层状结构,层与层之间也是通过微弱的范德华力相连在一起,层间距为0.615 nm。作者首次利用壳聚糖辅助液相剥离块状二硫化钼(MoS_2),然后再经过高温煅烧与氢氧化钾活化得到了MoS_2/氮掺杂的多孔碳的复合材料,并将其应用于锂离子电池中。在锂离子电池测试中,当电流密度为100 m A g~(-1),其初始比容量达到了1820 m Ah g~(-1),充放电50圈后,其容量依然可以维持在1260 m Ah g~(-1)。令人可喜的是,该材料在电流密度为5 A g~(-1)时,循环1000次后容量可以保持在496 m Ah g~(-1)。如此好的锂电性能,可能是归因于多孔碳缩短了锂离子的传输距离和电子的扩散距离,同时液相剥离得到的MoS_2纳米片可以为锂离子的嵌入与脱出提供更多的活性位点。(4)基于对锂离子电池制约因素的分析,作者利用金属有机框架化合物(MOFs)作为前驱体合成了颗粒自组装形成的尖晶石结构的层状Zn Co_2O_4纳米片。本文利用8-羟基喹啉作为有机配体和Zn~(2+)以及Co~(2+)络合形成片状的金属有机框架化合物(MOFs),然后在空气中煅烧得到颗粒自组装形成的层状Zn Co_2O_4纳米片。在形成MOFs的过程中,8-羟基喹啉的大π键的存在使得前驱体形成片状结构,而后在高温煅烧的过程中π键断裂,得到了颗粒自组装形成的层状Zn Co_2O_4纳米片。当Zn Co_2O_4纳米片作为锂离子负极材料时,在电流密度为100 m A g~(-1),充放电循环50圈后其比容量依然高达1640.8 m Ah g~(-1)。优异的储锂性能可归因于Zn Co_2O_4纳米片具有大的比表面积(118 m~2 g~(-1)),这样便拥有了更多的活性位点供锂离子的嵌入与脱出,其次提高了与电解液的接触面积,片状的Zn Co_2O_4可以缓解循环过程中的体积膨胀。
[Abstract]:With the progress and development of the society, the consumption of energy is also increasing, and the problem of environmental pollution is becoming more and more prominent. In order to meet the needs of human production and life, a new type of clean energy is needed, and the new energy must be regenerated and environmentally friendly. Pool and supercapacitor are three important ways to solve these problems. Photocatalytic hydrogen production is an important way to convert solar energy into clean and environmentally friendly hydrogen. It can not only alleviate the increasingly serious energy crisis but also solve environmental pollution. Lithium ion batteries have long cycle life and high energy density. As an efficient energy storage and conversion device, it has been widely used in portable electronic equipment and electric vehicles as a kind of efficient energy storage and conversion device. As another efficient and safe and clean energy storage and conversion device, the supercapacitor has high power density, long life and fast charging and discharging. The aim of this paper is to design new electrode materials and photocatalysts for the development of energy conversion. The purpose of this paper is to design and develop the photocatalytic hydrogen production, lithium ion battery and supercapacitor by analyzing the factors that restrict the performance of the photocatalyst and the electrode material. The main contents of this paper are as follows: (1) g-C_3N_4 has been widely studied because of its many advantages such as low price, non metal composition, stability and high efficiency of photocatalytic activity. The g-C_3N_4 of the body phase is not only smaller than the surface area, the photoelectric compound efficiency is high and the efficiency of the photocatalytic hydrogen production is also low, which seriously restricts the application of g-C_3N_4 in the photocatalytic hydrogen production. Based on this, the author obtained the body phase g-C_3N_4 by pyrolysis of melamine at high temperature, and then the dispersed g-C_3N_4 nanometers were obtained through the acid treatment and the liquid phase stripping. Finally, a layered porous g-C_3N_4 (HS g-C_3N_4-O) with a surface area up to 348 m~2 g~ (-1) is obtained by Photo-Fenton reaction. The band gap value of HS g-C_3N_4-O is found to be only 2.434 e V, which is far lower than that of the body. This may be because oxygen atoms are more than a nitrogen atom. In addition to providing additional electrons instead of nitrogen atoms, it is shown that HS g-C_3N_4-O has better transmission characteristics and more visible light capture ability, effectively reducing the recombination of photogenerated electrons and holes, and increasing the hydrogen production rate of.HS g-C_3N_4-O to 202.56 umol H-1, far higher than the bulk phase g-C_3N_4 (70.6). 5 umol h-1) and g-C_3N_4 nanoscale (122.56 umol h-1). (2) based on the understanding of the electrical conductivity of the pseudosacp electrode material and the low capacity of the electrical double layer capacitance electrode material, the author first synthesized the hybrid material of the carbon material and the polyaniline (PANI) sandwich structure using the metal organic frame compound MOFs. It is used in supercapacitor testing to find that it has good electrochemical performance. Metal organic frame compound (MOFs) is a new type of porous material formed by self assembly of organic ligands and metal ions or metal ions. In recent years, carbon materials have been obtained by MOFs as a template or precursor, and it has been gradually caused by people. In addition, polyaniline (PANI), as a pseudacapacitor material, is considered to be a highly developed pseudo capacitance supercapacitor electrode material because of its advantages of easy to get raw materials and simple synthesis. This paper uses 8- hydroxyquinoline as an organic ligand and metal ion Zn~ (2+) to form MOFs as a precursor and then passes through. A new type of sandwich hybrid material is formed by a high temperature calcined carbon material and in situ polymerization with polyaniline. When the power density is 1A g~ (-1), the specific capacitance reaches 477 F g~ (-1). After 100 charging and discharging cycles, the specific capacitance is only 10% less than that, indicating that the material has good cyclic stability. The excellent electrochemical performance may be because the sandwich structure effectively relieves the volume expansion and polarization of the electrode during the cycle process. Secondly, the carbon material can effectively improve the conductivity of the composite, while the pseudopoacitive polyaniline can improve the capacity of the composite. (3) the traditional lithium ion battery makes it possible to improve the capacity of the composite. The cathode material used is graphite, while the theoretical lithium storage capacity of the graphite is only 372 m Ah g~ (-1), which seriously restricts the application of lithium ion batteries on the next generation of electrical equipment. Therefore, a new type of high capacity lithium ion battery negative electrode is designed. In many negative electrode materials, the two layer structure is vulcanized. Molybdenum (MoS_2) is widely concerned by the researchers because of its theoretical capacity of 670 m Ah g~ (-1). Molybdenum disulfide (MoS_2) has a layered structure similar to graphene, and the layer and layer are connected by a weak van Edward force. The interval is 0.615 nm. by the author for the first time using chitosan assisted liquid to peel bulk molybdenum disulfide (MoS_2). After high temperature calcination and potassium hydroxide activation, MoS_2/ nitrogen doped porous carbon composite material was obtained and applied to lithium ion battery. In lithium ion battery test, when the current density is 100 m A g~ (-1), its initial specific capacity reaches 1820 m Ah g~ (-1), and after charging and discharging 50 cycles, its capacity can still be maintained at 1260 m Ah g~. (-1). It is gratifying that the material can be maintained at 496 m Ah g~ (-1) after 1000 cycles when the current density is 5 A g~ (-1). The good lithium electrical properties may be attributed to the porous carbon shortening the transmission distance of the lithium ion and the diffusion distance of the electrons, and the liquid phase stripping of the MoS_2 nanoscale can be embedded with the lithium ion. 4. (4) based on the analysis of the restriction factors of lithium ion batteries, the author syntheses the layered Zn Co_2O_4 nanoscale of the spinel structure formed by the self assembly of the metal organic frame compound (MOFs). This paper uses 8- hydroxyquinoline as an organic ligand and Zn~ (2+) and Co~ (2+) complex formation. The sheet metal organic frame compound (MOFs) is then calcined in the air to get the layered Zn Co_2O_4 nanoscale formed by the self-assembly of the particles. In the process of forming MOFs, the existence of the large pi bond of 8- hydroxyl quinoline causes the precursor to form a slice like structure, and then the pi bond is broken in the calcined process of high temperature, and the layer formed by the particle self assembly is obtained. When Zn Co_2O_4 nanoscale is a lithium ion anode material, the current density is 100 m A g~ (-1), and the specific capacity is still up to 1640.8 m Ah g~ (-1) after 50 cycles of charge discharge cycle. The excellent lithium storage property is attributable to the large specific surface area (118). The insertion and removal of lithium ions by sex sites increased the contact area with the electrolyte, and flake Zn Co_2O_4 could ease the volume expansion during cycling.

【学位授予单位】：上海电力学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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