基于生物质的纳米孔碳复合材料的制备及电容性能研究

发布时间：2018-06-27 09:51

  本文选题：生物质多孔碳 + 超级电容器　； 参考：《上海交通大学》2015年博士论文

【摘要】：近年来,随着工业化的快速发展,人口数量的急剧增加和矿石燃料(煤、石油和天然气等)的不断消耗,能源短缺和环境污染等问题日益严重。因此,清洁高效地利用能源成为解决上述问题的关键。超级电容器是一种新型的电能存储器件,具有功率密度高(10kWkg~(-1))、循环寿命长(100,000次循环)及倍率性能优越等特性,在工业、运输业和军事上得到广泛应用。超级电容器主要有两种类型,即双电层超级电容器和赝电容超级电容器。前者利用离子电荷的物理吸附存储电能,其中电极材料主要是碳材料,如活性炭,石墨烯和碳纳米管等。它们具有优异的导电性,因此,其倍率性能优异;但受限于其比表面积,其比电容较小(300Fg~(-1)),能量密度也较小(10Whkg~(-1))。赝电容超级电容器主要过渡金属化合物,利用过渡金属的价态可变化性能(可逆氧化还原反应)实现电荷的存储与释放。赝电容电极材料比碳材料具有更高的比电容和能量密度,但是其较差的导电性降低了其倍率性能和功率密度,此外其循环性能也比碳材料差。因此,基于以上两类电容器电极材料的性能,研制高性能的碳基复合材料成为目前研究的热点。尽管新兴的石墨烯和碳纳米管等得到很多关注,但其电容性能与活性炭接近,且其制作成本远高于活性炭,故而现阶段尚不能实现大规模的工业化生产。并且,它们本身易发生堆叠现象,尤其在复合赝电容材料后,比表面积大幅下降,造成双电层效应随之亦大幅降低,不利于双层电容器电荷存储效应与赝电容效应的有效发挥。鉴于此,一方面为了寻求可大规模产业化生产并具有优异电容特性的碳基电极材料,另一方面为实现在此碳基上与其它赝电容纳米功能相复合以进一步提高电容特性的目的,本论文开展了基于生物质碳材料的纳米复合电极的制备及电容性能研究。自然界历经亿万年,进化了数目繁多的多形态、多尺度、多维数的生物质材料。这些生物质为人类简易、廉价获取碳材料提供了丰富的资源。经过简单的碳化与活化工艺制备获得的生物质纳米孔碳基,不仅生产成本低,并且由于其本身具有的多孔结构和表面特性,即使在复合纳米功能相之后仍能发挥部分双电层效应;大的比表面积可为功能相离子的复合提供更多的沉积位点,促进复合相在碳基上的分散型分布,最终提高复合材料整体的电容性能。本文充分利用生物质纳米孔碳作为基底,原位引入纳米功能相,制备出基于生物质碳的先进多孔碳复合电极材料。重点研究了生物质碳表面复合功能相的制备工艺,围绕具有层、颗粒、管等典型形貌的纳米功能相,研究了双层电容的碳基与赝电容功能相的耦合效应。主要内容和结论如下:一、生物质纳米孔碳表面原位复合纳米金属颗粒工艺研究不同生物质制备的纳米孔碳材料存在表面物理、化学性质及微观结构上的较大差异。因此,甄选合适生物质碳基和复合工艺方法是实现生物质碳与纳米功能相复合的重点。本文选取四种生物质纳米孔碳,分别采用浸渍法、水浴沉积沉淀法和微波沉积沉淀法研究了Co纳米颗粒在生物质碳表面的沉积状况,最终确立了具有大孔容、均一化孔径分布和大量含氧官能团的竹质纳米孔碳作为生物质碳基,通过微波沉积沉淀法可实现Co纳米颗粒在碳表面上的均匀沉积。研究发现,选取Co(NO_3)_2·6H_2O为前驱离子溶液,溶液浓度3.4mM、与尿素溶液浓度配比1:10、超声时间3min、使用2450MHz的700W低温微波加热反应12min为最优微波沉积沉淀实验参数,可在纳米孔竹碳上实现分散性很高的纳米金属颗粒功能相的复合,为下步二元、三元生物质多维纳米孔碳杂化材料的制备奠定实验基础。二、纳米薄片Co(OH)_2/生物质纳米孔碳纳米复合材料电极制备及性能研究为了提高薄片Co(OH)_2的活性物质表面利用率,本文通过快速、廉价有效的微波沉积法将花状α-Co(OH)_2纳米片原位生长于生物质纳米孔碳基上,应用于超级电容器。碳基的存在促进了具有赝电容特性的Co(OH)_2纳米片的分散,使得Co(OH)_2纳米片层厚度明显降低,平均纳米片层厚度仅为5-9nm左右;并且,碳基的多孔结构在充放电中为电荷转移提供了更加充足的通道。这个杂化结构的比电容可在0.1Ag~(-1)下达到345Fg~(-1),并可在高电流密度5Ag~(-1)时保持284Fg~(-1)。另外,由于构建的杂化结构稳定性较好,使得复合材料在5Ag~(-1)时充放电5000次后比电容的容量衰减仅为14%。这个优良的电化学性能归因于多孔碳基和赝电容特性的Co(OH)_2纳米片之间的协同作用。三、低温快速合成高度分散、尺寸可控的Co_3O_4颗粒/生物质纳米孔炭复合材料电极制备及性能研究为了提高活性物质的利用率,降低复合的纳米功能相对碳基表面的堵塞,使得赝电容效应和碳基的双电层电荷存储效应能够充分发挥,本文研究了Co_3O_4纳米级颗粒与生物质纳米孔碳的复合。应用快速的微波沉积沉淀法在活性竹炭上负载均匀分布的Co_3O_4纳米颗粒并应用于超级电容器。Co_3O_4纳米颗粒尺寸可通过碳基的不同预氧化处理控制在几至几十纳米之间。碳基的双电层电容和锚定的Co_3O_4纳米颗粒的赝电容性能协同作用决定了杂化材料的电化学性能,其中,Co_3O_4纳米颗粒的尺寸和负载量影响着Co_3O_4纳米颗粒在杂化材料中的赝电容贡献。当纳米颗粒平均尺寸约为7nm且负载量16.4wt%时,复合材料在6M的KOH中0.1Ag~(-1)时测试的比电容值可达491Fg~(-1)。另外,合成的二元杂化材料在高电流密度5Ag~(-1)时循环5000次充放电后的比电容衰减仅为11%,表明了Co_3O_4纳米颗粒与碳基之间较强的结合力。四、多级三元碳纳米管/纳米金属/生物质纳米孔碳杂化复合电极材料的制备及性能研究为了进一步提高材料的整体电容,本文在以上的研究基础上引入了碳纳米管的纳米功能相来提供额外的比表面积存储电荷,并形成良好的导电网络。我们采用微波法在活性竹炭基上沉积均匀分散的纳米颗粒,再通过化学气相沉积以此为生长位点原位生长开口的碳纳米管,合成了碳纳米管、纳米金属和活性炭的多级三元杂化材料。碳管与活性炭表面通过纳米颗粒作为节点紧密结合。这个独特的三维杂化结构使此复合材料表现出相当大的比电容(1Ag~(-1)时为440Fg~(-1))及优良的倍率性能(5Ag~(-1)相对于1Ag~(-1)时,97%)。另外,三元杂化材料在5Ag~(-1)时,循环3000次后仍可保留98.4%的初始电容,表明了其优异的循环稳定性。除了较高的比表面积,这样优异的电容性能主要归因于:开口的碳纳米管(5~(-1)2nm)可提供更有效的离子通道;互相交错的纳米管导电网络结构促进了电子的运输;超细小的纳米金属颗粒(3-9nm)提供了赝电容,表明了双电层电容和赝电容反应共同产生的协同效应有利于提高总电容性能。综上所述,本研究以低成本、来源广、已工业化的生物质纳米孔碳为多孔支撑基底,研究了碳基原位微波复合纳米功能相的制备方法,实现了生物质纳米孔碳与不同纳米功能相(纳米薄片Co(OH)_2、颗粒Co_3O_4、碳纳米管/纳米金属)的二元、三元复合电极。复合电极具有分级多孔、导电性好和纳米功能相分散均匀的结构特点,因此有效实现了赝电容、双电层储能的协同作用。微波沉积沉淀法具有耗时短、加热高效均匀的特点,将大大提高电极材料的生产效率。同时,本文研究了不同种类的具有赝电容特性的纳米功能相与碳基复合后产生的协同作用对于整体电容性能的影响,为基于生物质的先进功能电极材料的开发、构筑和应用提供了更为广阔的研究空间。
[Abstract]:In recent years, with the rapid development of industrialization, the rapid increase of population and the continuous consumption of ore fuel (coal, petroleum and natural gas), energy shortage and environmental pollution are becoming more and more serious. Therefore, the clean and efficient use of energy has become the key to solve the above problems. With high power density (10kWkg~ (-1)), long cycle life (100000 cycles) and superior performance, it is widely used in industry, transportation and military. Supercapacitors mainly have two types, namely, double layer supercapacitor and pseudacapacitor supercapacitor. The former uses the physical adsorption of ion charge to store electrical energy and electricity. Polar materials are mainly carbon materials, such as activated charcoal, graphene and carbon nanotubes. They have excellent conductivity, so they have excellent multiplying performance; but limited to their specific surface area, their specific capacitance is smaller (300Fg~ (-1)), and the energy density is smaller (10Whkg~ (-1)). The state variable performance (reversible redox reaction) realizes the storage and release of the charge. The pseudopotential electrode material has a higher specific capacitance and energy density than the carbon material, but its poor conductivity reduces its multiplying performance and power density, and its cycle performance is worse than that of the carbon material. Therefore, based on the above two kinds of capacitor electrode materials The performance of material and the development of high performance carbon based composites have become a hot spot of research. Although new graphene and carbon nanotubes have received much attention, their capacitive performance is close to activated carbon, and the production cost is much higher than that of activated carbon. Therefore, it is not yet possible to achieve large-scale industrial production at this stage. And they are easy to happen in themselves. The stacking phenomenon, especially after the composite pseudopotential material, has a significant reduction in specific surface area, resulting in a large reduction in the double layer effect, which is not conducive to the effective use of the charge storage and pseudo capacitance effects of a double layer capacitor. On the other hand, in order to combine with other pseudosacacious nanoscale functions on this carbon base to further improve the capacitance characteristics, the preparation and capacitive performance of nanocomposite electrodes based on biomass carbon materials have been studied in this paper. Materials. These biomass provides a rich resource for simple human, cheap carbon materials. The biomass nanoscale carbon based on simple carbonization and activation process is not only low in production cost, but also partly because of its porous structure and surface properties, even after the composite nanoscale phase. The large specific surface area can provide more sedimentary loci for the composite of functional phase ions, promote the dispersive distribution of the composite on the carbon base, and ultimately improve the capacitance performance of the composite. This paper makes full use of the biomass nanoscale Kong Tan as the substrate and in situ introduction of nanoscale phase to prepare the advanced carbon based biomass. Porous carbon composite electrode material. The preparation technology of composite functional phase of biomass carbon surface was studied. The coupling effect of carbon based and pseudosacacp function of double layer capacitance was studied. The main contents and conclusions are as follows: first, in situ composite nano gold on the surface of biomass carbon nanohole carbon. There is a large difference in surface physics, chemical properties and microstructure of the nanoscale carbon materials prepared by different biomass. Therefore, the selection of suitable carbon based and composite technology is the key to the realization of the combination of biomass carbon and nanoscale function. In this paper, four kinds of biomass carbon nanoscale were selected, and the impregnation method was adopted respectively. The deposition of Co nanoparticles on the surface of biomass carbon was studied by water bath deposition precipitation method and microwave deposition method. Finally, a large pore volume, homogeneous pore size distribution and a large number of oxygen functional groups were established as carbon based carbon nanoscale. By microwave deposition precipitation method, the uniformity of Co nanoparticles on the carbon surface could be realized. The study found that Co (NO_3) _2 / 6H_2O was selected as the precursor solution, the concentration of solution was 3.4mM, the ratio of the urea solution at 1:10, the ultrasonic time 3min, the 2450MHz 700W low temperature microwave heating reaction 12min as the optimum microwave deposition experimental parameter, and the nanometer Kong Zhu carbon could be used to realize the high dispersive nano metal particle function phase on the nano Kong Zhu carbon. Composite, for the preparation of two yuan, three yuan biomass multi-dimensional nano porous carbon hybrid materials, two, nanoscale Co (OH) _2/ biomass nanoscale carbon nanocomposites electrode preparation and performance study in order to improve the surface utilization of Co (OH) _2 active material to improve the surface utilization, this paper through the rapid, cheap and effective microwave deposition of the flower The -Co (OH) _2 nanometers are in situ grown on the carbon base of biomass nanoscale, and are applied to the supercapacitor. The existence of carbon base promotes the dispersion of Co (OH) _2 nanoscale with pseudo capacitance. The thickness of Co (OH) _2 nanoscale layer is obviously reduced and the average thickness of the nanoscale layer is only about 5-9nm. The charge transfer provides a more sufficient channel. The specific capacitance of this hybrid structure can reach 345Fg~ (-1) under 0.1Ag~ (-1), and can maintain 284Fg~ (-1) at a high current density 5Ag~ (-1). In addition, the composite structure has a better stability of the hybrid structure, which reduces the capacity of the composite at 5Ag~ (-1) for 5000 times and the capacity attenuation is only 14%.. The excellent electrochemical properties are attributed to the synergism between Co (OH) _2 nanoscale films with porous carbon and pseudosacacp properties. Three, rapid synthesis of highly dispersed low temperature, size controlled Co_3O_4 particles / biomass nano pore carbon composite electrode preparation and performance study in order to improve the utilization of active substances and reduce the composite nanoscale phase The blockage of the carbon based surface makes the effect of the pseudo capacitance effect and the carbon based double layer charge storage effect can be fully played. In this paper, the composite of Co_3O_4 nanoscale particles and biomass nanoscale carbon is studied. The Co_3O_4 nanoparticles with uniform distribution on active bamboo charcoal have been applied to the super capacitor.Co by rapid microwave deposition and precipitation method. The size of _3O_4 nanoparticles can be controlled by several to dozens of nanometers by carbon based preoxidation. The synergistic effect of carbon based double layer capacitance and the pseudo capacitance of anchored Co_3O_4 nanoparticles determines the electrochemical properties of the hybrid materials. The size and load of Co_3O_4 nanoparticles affect the Co_3O_4 nanoparticles in the nano particles. The contribution of pseudo capacitance in hybrid materials. When the average size of the nanoparticles is about 7Nm and the load is 16.4wt%, the specific capacitance of the composite can reach 491Fg~ (-1) at 0.1Ag~ (-1) in the KOH of 6M. In addition, the specific capacitance attenuation of the synthesized two element hybrid material at the high current density 5Ag~ (-1) is only 11% after 5000 cycles of charge discharge, indicating Co_3. The strong binding force between the O_4 nanoparticles and the carbon base. Four, the preparation and properties of multi-stage three yuan carbon nanotubes / nanoscale / biomass carbon hybrid composite electrode materials to further improve the overall capacitance of the material. Based on the above research, the nano functional phase of carbon nanometers is introduced to provide an additional specific meter. The area stores charge and forms a good conductive network. We use microwave method to deposit evenly dispersed nanoparticles on active bamboo charcoal, and then by chemical vapor deposition to grow open carbon nanotubes in situ at the growth site. The multistage three element hybrid materials of carbon nanotubes, nanoscale metal and activated carbon are synthesized. Carbon tube and activity have been synthesized. The carbon surface is tightly combined with the nanoparticles as nodes. This unique three-dimensional hybrid structure makes the composite exhibit considerable specific capacitance (1Ag~ (-1) for 440Fg~ (-1)) and excellent multiplier performance (5Ag~ (-1) relative to 1Ag~ (-1), 97%). In addition, three yuan hybrid materials can remain at the beginning of 98.4% after 3000 cycles in 5Ag~ (-1). In addition to the high specific surface area, the excellent capacitive performance is mainly attributable to the fact that the open carbon nanotube (5~ (-1) 2nm) provides more effective ion channels; the interlaced nanotube conductive network structure promotes the transport of the electric energy; the ultra fine nano metal particles (3-9nm) provide Pseudo capacitance shows that the synergistic effect produced by the double layer capacitance and the pseudosacacious reaction is beneficial to the improvement of the total capacitance. In this study, the preparation method of carbon based in situ microwave compound nano functional phase is studied with low cost, wide source and industrialized biomass nanoscale carbon as the porous support substrate. Mica carbon and different nanoscale phase (nanoscale Co (OH) _2, particle Co_3O_4, carbon nanotube / nano metal) are two yuan and three element composite electrodes. The composite electrode has the structure characteristics of the porous structure, good conductivity and the dispersion and uniformity of nanoscale function. Therefore, the synergistic effect of pseudo capacitance and double layer energy storage is effectively realized. Microwave deposition precipitation method The characteristics of short time and high efficiency will greatly improve the production efficiency of the electrode materials. At the same time, the effects of the synergistic effects of different kinds of nano functional phase and carbon based composite on the overall capacitive performance are studied, and the development of advanced functional electrode materials based on raw materials and the construction and construction of the materials are also studied. The application provides a broader research space.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;TM53
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本文编号：2073521