碳纳米管—石墨烯异质结构及复合物的构筑与其超电容性能研究

发布时间：2018-09-12 09:51

【摘要】：随着清洁能源的开发和利用，能源储备显得尤为重要，开发高效的能源储存设备迫在眉睫。超级电容器是一种新型的能量储存/转化装置，其较高的功率密度以及超长的循环寿命深受研究者们的亲睐。超级电容器的电容以及电荷的存储主要取决于电极材料的选择。在过去的十年中，碳纳米管(Carbon nanotubes, CNTs)因其良好的机械性能，化学稳定性和高导电性等优点，常作为典型的双电层超级电容器电极材料。然而，微米长度的CNTs，尤其多壁碳纳米管(Multi-walled carbonnanotubes, MWCNTs)之间容易交织缠绕形成“绳索”，且碳纳米管两端封闭结构，使得电解质中离子无法接触碳纳米管内壁。为了提高碳纳米管作为超级电容器电极材料的电化学性能，对其进行切割、掺杂或复合是必要的。在本论文的研究工作中，我们采用修饰的Hummer方法切割打开MWCNTs得到碳纳米管-氧化石墨烯异质结构(Carbon nanotube graphene oxideheterogeneous structure, CNTGO)，以此作为基底材料，制备了具有高性能的氮掺杂碳纳米管-石墨烯复合物(Nitrogen-doped carbon nanotube reduced grapheneoxide heterogeneous carbon composites, N-CNTRGO)和氧化镍/碳纳米管-石墨烯复合材料(NiO/CNTRGO)。利用相关分析测试手段对三种材料的形貌、结构和组成进行了分析表征，并采用电化学测试方法对N-CNTRGO和NiO/CNTRGO的电化学性能进行了详细研究。主要内容概括如下：通过修饰的Hummer法切割MWCNTs，得到水分散性的CNTGO，再经后续热处理得到碳纳米管-还原氧化石墨烯异质结构(Carbon nanotube reducedgraphene oxide heterogeneous structure, CNTRGO)。研究结果表明，该材料是由短碳纳米管和碳纳米管管壁破裂后形成的多层石墨烯组成；发现氧化剂的用量是影响CNTRGO电化学性能的关键因素，当氧化剂(KMnO4)和MWCNTs的质量比是4:1时，CNTRGO电极具有最大的比电容。在1mol L-1H2SO4和1mol L-1KOH电解液中，电流密度为1Ag-1时CNTRGO的比电容分别达到157和183F g-1，此值约是MWCNTs在同等条件下比电容的9倍。此外，该材料在1mol L-1H2SO4电解液中，电流密度为1Ag-1时持续进行恒电流充放电3000次，发现其比电容没有衰减，而在1mol L-1KOH电解液中，，3000次循环后比电容仍能保持初始值的82.5%。说明该材料电化学性能优良，是一种有潜力的超级电容器电极材料。采用简单的水热法，制备了氮掺杂碳纳米管-石墨烯复合物(N-CNTRGO)。在N-CNTRGO合成过程中，水合肼作为还原剂(CNTGO还原为CNTRGO)和氮源，pH=10的氨水溶液作为反应溶剂。研究结果表明，水热温度对其结构、含氮量以及电化学性能有显著影响。当反应温度为120°C时，N-CNTRGO材料含氮量高达3.48%，在1Ag-1时，比电容值为269.1F g-1，经过5000次循环后，其比电容仍能保持81%。采用简单的溶剂热法以及后续热处理过程，制备了氧化镍/碳纳米管-石墨烯复合材料(NiO/CNTRGO)。在NiO/CNTRGO复合过程中，CNTRGO作为基底生长NiO，同时NiO可以有效的避免CNTRGO的团聚行为。当复合材料NiO/CNTRGO(NiO占NiO/CNTRGO总质量的77.5%)作为超级电容器电极材料时呈现出优越的电化学性能：在电流密度为1A g-1时，比电容为1010F g-1。此外，该复合材料经过3000次循环后，比电容仍然能保持初始值的68%。
[Abstract]:With the development and utilization of clean energy, energy reserve becomes more and more important. It is urgent to develop efficient energy storage equipment. Supercapacitor is a new type of energy storage/conversion device. Its high power density and long cycle life are favored by researchers. In the past decade, carbon nanotubes (CNTs) have been used as typical electrode materials for double-layer supercapacitors because of their excellent mechanical properties, chemical stability and high conductivity. MWCNTs are easily intertwined and wound to form "ropes" and the two ends of the carbon nanotubes are enclosed so that the ions in the electrolyte can not touch the inner wall of the carbon nanotubes. In order to improve the electrochemical performance of carbon nanotubes as electrode materials for supercapacitors, it is necessary to cut, dope or compound the carbon nanotubes.
In this paper, we prepared carbon nanotube graphene oxide heterogeneous structure (CNTGO) by cutting open MWCNTs with modified Hammer method. Nitrogen-doped carbon nanotube-graphene composites (Nitrogen-doped graphene composites) with high performance were prepared by using CNTGO as substrate material. Carbon nanotube reduced graphene oxide heterogeneous carbon composites (N-CNTRGO) and nickel oxide/carbon nanotube-graphene composites (NiO/CNTRGO). The morphologies, structures and compositions of the three materials were characterized by correlation analysis. The electrochemistry of N-CNTRGO and NiO/CNTRGO was studied by electrochemical methods. Performance is studied in detail. The main contents are summarized as follows:
Modified HUMmer method was used to cut MWCNTs to obtain water-dispersible CNTGO. Carbon nanotube reduced graphene oxide heterogeneous structure (CNTRGO) was obtained by subsequent heat treatment. The results showed that the material was formed by the rupture of short carbon nanotubes and the wall of carbon nanotubes. It was found that the amount of oxidant was the key factor affecting the electrochemical performance of CNTRGO. When the mass ratio of KMnO4 to MWCNTs was 4:1, the CNTRGO electrode had the largest specific capacitance. In 1mol L-1H2SO4 and 1mol L-1KOH electrolytes, the specific capacitance of CNTRGO reached 157 and 183F g-1, respectively, when the current density was 1Ag-1. The specific capacitance of the material was about 9 times as large as that of MWCNTs under the same conditions. In addition, the material was charged and discharged continuously for 3000 times in 1mol L-1H2SO4 electrolyte with current density of 1Ag-1. It was found that the specific capacitance did not decay, but remained 82.5% of its initial value in 1mol L-1KOH electrolyte after 3000 cycles. Excellent, it is a potential supercapacitor electrode material.
Nitrogen-doped carbon nanotubes-graphene composites (N-CNTRGO) were prepared by a simple hydrothermal method. Hydrazine hydrate was used as a reducing agent (CNTGO reduced to CNTRGO) and nitrogen source, and ammonia solution with pH=10 was used as a solvent in the synthesis of N-CNTRGO. The nitrogen content of N-CNTRGO is as high as 3.48% when the reaction temperature is 120 degrees C. The specific capacitance of N-CNTRGO is 269.1Fg-1 at 1Ag-1. After 5000 cycles, the specific capacitance of N-CNTRGO can still keep 81%.
NiO/CNTRGO composites (NiO/CNTRGO) were prepared by simple solvothermal method and subsequent heat treatment. In the NiO/CNTRGO composite process, CNTRGO was used as substrate to grow NiO and NiO could effectively avoid the aggregation behavior of CNTRGO. When NiO/CNTRGO composites (NiO accounted for 77.5% of the total mass of NiO/CNTRGO) were used as super-composites. The electrode material of grade-I capacitor exhibits excellent electrochemical performance: the specific capacitance is 1010Fg-1 at current density of 1A g-1. In addition, the specific capacitance of the composite can still keep 68% of the initial value after 3000 cycles.
【学位授予单位】：西北师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：O613.71;TM53

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