氮掺杂石墨烯及其复合材料相关性能的研究

发布时间：2018-01-11 13:25

本文关键词：氮掺杂石墨烯及其复合材料相关性能的研究　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：石墨烯自从在2004年被首次制备出来,在短短几年内,就成为材料科学领域的研究热点。石墨烯也因其优异的物理、化学性能而被应用到诸如储能、化工、光电、传感等许多领域,石墨烯产业目前也处于快速发展和成熟的过程中。随着应用的进一步深入,未经改性的纯石墨烯已经很难满足需求,比如:本征石墨烯的零带隙特性,限制了其在半导体领域的应用;石墨烯自身的电化学性能无法完全满足新一代储能器件的要求,需要和特定材料进行复合以提升综合性能。掺杂是改变石墨烯特性最有效的手段之一。本论文从理论上研究了包括氮原子在内的几种非金属原子插层对石墨烯的性能调控作用,还分别实验制备了氮掺杂石墨烯和二氧化锡纳米晶体以及磷酸钒锂纳米颗粒的复合材料,测试了复合材料的性能。本论文主要研究内容如下:(1)现有石墨烯掺杂的理论研究主要关注替代掺杂和缺陷修饰,本论文对石墨烯插层掺杂的理论研究进行了有效补充,提出了SiC (0001)面上外延生长的双层石墨烯被包括氮原子在内的非金属原子插层的模型,采用第一性原理分析的方法研究了其能带特性和界面磁性。为了作对比,我们先分别研究了氟,氯,氧,氮原子可能的插层方式以及插层前后的能带和界面磁性等的变化,然后汇总进行了横向比较。发现通过增加氟原子的吸附浓度,可以精确地将体系从n型掺杂调制到电中性,再调制到p型掺杂,同时界面磁性也跟着发生变化。氯掺杂特性和氟掺杂类似。氧原子修饰则能产生p型掺杂。氮原子修饰能给石墨烯打开一个小的带隙。该部分研究对石墨烯性能调控具有一定价值。(2)采用水合肼蒸气还原的方法,制备出了二氧化锡纳米颗粒晶体和氮掺杂石墨烯的复合材料,并用X射线衍射图,XPS能谱图,透射电镜图,拉曼光谱等进行了表征,研究了复合材料的形貌、微观结构、成分。二氧化锡纳米颗粒负极虽然具有较高的理论容量,但循环稳定性极差。为了探究氮掺杂石墨烯对二氧化锡电化学性能的影响,我们将该复合材料和对照组的二氧化锡纳米颗粒制备成扣式电池负极,做了比容量和循环性能等方面的测试。相对二氧化锡基负极而言,该复合材料负极具有更高的比容量和更稳定的循环性能。(3)实验并示范了一种能快速制备氮掺杂石墨烯和碳包覆磷酸钒锂纳米颗粒复合材料的简单方法。为了作对比,还制备了石墨烯和碳包覆的磷酸钒锂纳米颗粒的复合材料,以及碳包覆的磷酸钒锂纳米颗粒材料。表征了三组样品的形貌、微观结构和成分。并对三组正极材料进行了循环性能、倍率性能、长周期稳定性等测试,测试结果的比较可以进一步认识氮掺杂对石墨烯的性能影响,以及氮掺杂石墨烯对磷酸钒锂纳米颗粒的电化学性能的影响。该部分研究对于磷酸钒锂正极材料在高倍率下容量偏低的问题,以及循环性能的提升均提出了解决方案。
[Abstract]:Since graphene was first prepared in 2004, in a few years, it has become a research hotspot in the field of materials science. Graphene is also due to their excellent physical and chemical properties and has been applied in energy storage, chemical industry, optoelectronics, sensor and so many fields, graphene industry is also in rapid development and mature in the process. With the further application, without the pure graphene modified has been difficult to meet the demand, such as: zero band gap intrinsic graphene, which limits its application in the semiconductor field; the electrochemical properties of graphene itself can not fully meet the requirements of the new generation device, need and the specific composite materials to enhance the comprehensive performance. Doping is one of the most effective means to change the graphene characteristics. This thesis studies several nitrogen atoms, including non metal atom Intercalation Performance regulation of graphene Also, respectively. Experiment of composite nitrogen doped graphene oxide and tin nano crystal two and lithium vanadium phosphate nanoparticles were prepared. The properties of the composites were tested. The main research contents of this paper are as follows: (1) the theory research mainly focus on the doping and defects of existing modified graphene doped, theoretical study of this thesis intercalation doping on graphene were effectively, put forward the SiC (0001) non metal atom bilayer graphene epitaxial growth on the surface of the nitrogen atoms are included, inserted layer model, adopting the analysis method of the first principle of the band characteristics and interface magnetic. For comparison, we first were studied by fluorine, chlorine, oxygen, and nitrogen atoms may intercalation and intercalation before and after the changes of band and magnetic interface, and then summarized the horizontal comparison. Found by increasing the adsorption concentration of fluorine,. It will system from the N type doping modulation to the electrically neutral, then modulated to p type doping, while the interface magnetic changes. Chlorine doping characteristics and fluorine doping. Similar oxygen atoms can be modified P type doping. The nitrogen atom modification can open a small gap to the graphene. This part of research this has a certain value on the graphene performance regulation. (2) by using the method of hydrazine vapor reduction, prepared the composite two tin oxide nanoparticle crystals and nitrogen doped graphene, and using X ray diffraction and XPS spectrum, transmission electron microscope, Raman spectra were characterized, research the morphology, microstructure, composition of two tin oxide nanoparticles as anode. Although it has high theoretical capacity, but capacityfading. In order to study the influence of nitrogen doped graphene on the electrochemical properties of tin oxide two, the composite material and two in the control group Tin oxide nanoparticles prepared by button battery cathode, the specific capacity and cycle performance and other aspects of the test. The relative two tin oxide based anode, the composite electrode has higher capacity and more stable cycle performance. (3) the experiment and demonstration of a simple method for rapid preparation of nitrogen the doped graphene and carbon coated lithium vanadium phosphate nano particle composite material. For comparison, also prepared composite materials lithium vanadium phosphate nanoparticles and graphene coated with carbon, and carbon coated lithium vanadium phosphate nanoparticles. The characterization of the three groups of samples morphology, microstructure and composition. The three group of cathode material cycle performance, rate capability, long cycle stability test, comparison of test results to further understand the effects of nitrogen doping on the properties of graphene, and electrochemical nitrogen doped graphene lithium vanadium phosphate nanoparticles The influence of performance is studied. This part puts forward a solution to the problem of low capacity and high cycle performance of vanadium phosphate cathode material.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM912;TB33

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