形貌可控钴镍纳米金属复合氧化物的设计制备及超电容性能研究

发布时间：2018-07-15 18:20

【摘要】：能源问题是目前制约社会可持续发展的重要因素,人们对传统的化石能源的过度开发利用带来了一系列的环境污染问题,这已经严重威胁到了人类的生存与发展。人类在开发新型清洁能源的同时,对能源的储存与转化装置也显得尤为重要。作为一种新型储能设备,超级电容器具有较高的功率密度及较长的使用寿命也受到了人们广泛的关注。但是成本高、能量密度低等因素极大的限制了其发展,而电极材料是决定超级电容器性能的关键,因此开发新型价格低廉、高能量密度及高稳定性的电极材料是目前研究的重点。本文基于镍钴过渡金属元素及多壁碳纳米管等电极材料,以研制低成本、高比电容及高稳定性的超级电容器电极材料为目的,采用简易的合成方法和材料组合制备各种电极材料,并通过各种分析测试手段研究材料超电容性能。主要研究内容如下:第一、采用一种绿色环保合成方法、简单的制备工艺,即以稀释后的氨水作为反应试剂合成了过渡金属氧化物Co_3O_4和NiO,该催化剂具有典型的法拉第赝电容特性。以Co_3O_4为例将活性物质与导电剂乙炔黑按照不同的质量比例在1mol L-1的KOH电解质溶液中采用三电极测试系统进行电化学测试,结果显示当比例为8:1时电极材料具有最佳的电化学性能,Co_3O_4呈现出了典型的赝电容特性,在1 A g~(-1)的电流密度下比电容达到394 F g~(-1)。按照此比例对NiO进行测试,比电容达到了139 F g~(-1)。第二、将镍钴两种金属元素进行复合,考察了两种过渡金属间的协同效应对提高比电容性能的影响及作用机制。实验采用水热-高温煅烧的方法将钴和镍按照2:1的摩尔比例进行复合,通过调控煅烧温度150、250、350和450℃各3小时,运用X射线衍射(XRD)、热重分析(TGA)及扫描电子显微镜(SEM)等表征手段证明合成了具有片状结构的二元复合金属(氢)氧化物。进一步研究表明:煅烧温度的不同导致材料的脱水程度也不同,进而对材料的形貌及性能造成了很大的影响。通过对各个煅烧温度的样品材料进行电化学测试对比发现,在煅烧温度为250oC时的样品的无论是循环伏安测试还是恒电流充放电测试都表现出了较优异的性能,在扫描速度为10 m V s-1时高达1296 F g~(-1)的比电容,在1 A g~(-1)的电流密度下比电容高达1427 F g~(-1),即使电流密度增大到10 A g~(-1)时,比电容仍高达1270 F g~(-1),比电容仍然达到了89%的保持率。一般来说材料中镍钴的各自的含量对超级电容器性能存在较大的影响,在确定了最佳的煅烧温度之后,我们又对两种元素的复合比例进行探索,将钴和镍按照不同的摩尔比在同等的水热条件煅烧温度为250℃下进行制备,并对其进行了电化学测试。结果表明,镍钴不同的比例对电容性能产生了极大的影响,当钴镍比例为2:1时材料的性能达到最佳。最后将复合之后的样品材料的电化学性能与在同样条件下合成的单一的镍氧化物和钴氧化物进行对比实验,结果表明复合催化剂的电化学性能有了极大的提高,对其进行稳定性测试结果也表明在经过了10 A g~(-1)的大电流3000圈的循环之后,比电容仅仅衰减了7.7%,表现出了较优异的稳定性。这说明在水热-高温煅烧的制备工艺中,镍钴二者的复合极大的提高了材料的电容特性。第三、为了进一步提高镍钴氢氧化物的电化学性能,我们将合成的镍钴氢氧化物与MWCNTs进行物理性复合,并对二者的复合比例进行了探索。将二者按照不同的质量比例进行复合,对其进行电化学测试结果表明在复合比例为9:1时效果最好,在1mol L-1的KOH电解质溶液中1 A g~(-1)的电流密度下比电容高达1675 F g~(-1),与复合之前进行对比发现比电容有了很大的提高,表明具有管状结构的MWCNTs与片层结构的镍钴氢氧化物的复合极大的提高了材料的导电性能,使得材料的电容性能得到了进一步的提高。对其进行稳定性测试表明,经过3000圈循环后,电容保持率依然达93.2%,表现出了较好的稳定性。
[Abstract]:The energy problem is an important factor restricting the sustainable development of the society. People have brought a series of environmental pollution problems to the overexploitation and utilization of traditional fossil energy. This has seriously threatened the survival and development of human beings. At the same time, human beings are especially in the development of new clean energy and the storage and transformation of energy. As a new type of energy storage equipment, the supercapacitor has high power density and long service life. However, the high cost and low energy density limit the development of the supercapacitor, and the electrode material is the key to determine the capacity of the supercapacitor. Therefore, the development of new type is cheap and high energy. The electrode materials with high density and high stability are the focus of current research. Based on the electrode materials such as nickel cobalt transition metal elements and multi wall carbon nanotubes, this paper aims to prepare the electrode materials with low cost, high specific capacitance and high stability, and the preparation of various electrode materials by simple synthetic method and material combination. The main research contents are as follows: first, a green synthesis method, a simple preparation process, is used to synthesize the transition metal oxide Co_3O_4 and NiO with the diluted ammonia water as reagents. The catalyst has a typical Faraday pseudacapacitor property. Co_3O_4 is used as an example. The three electrode test system was used in the KOH electrolyte solution of 1mol L-1 with the active substance and acetylene black. The results showed that the electrode material had the best electrochemical performance when the ratio was 8:1, and the Co_3O_4 showed a typical pseudopotential characteristic and the ratio of the current density of the 1 A g~ (-1). The capacitance is 394 F g~ (-1). According to this proportion, the NiO is tested, the specific capacitance reaches 139 F g~ (-1). Second, the two metals of nickel and cobalt are combined to investigate the effect of the synergistic effect between the two kinds of transition metals on the performance of the specific capacitance and the mechanism of action. By controlling the calcining temperature of 150250350 and 450 degrees for 3 hours, X ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to demonstrate the synthesis of two element composite metal (hydrogen) oxides with flake structure. The further study shows that the different calcination temperatures lead to the dehydration of the materials. It has a great influence on the morphology and performance of the material. Through the electrochemical test of the sample materials at different calcination temperatures, it is found that the sample with a calcining temperature of 250oC has excellent performance in both cyclic voltammetry and constant current charge discharge test, and the scanning speed is 10 m. When V S-1 is up to 1296 F g~ (-1), the specific capacitance is up to 1427 F g~ (-1) at the current density of 1 A g~ (-1). Even if the current density increases to 10 A, the specific capacitance is still up to 1270, and the specific capacitance is still up to 89%. In general, the content of nickel and cobalt in the material is larger than that of the supercapacitor. After determining the optimum calcining temperature, we explored the compound ratio of the two elements and prepared the cobalt and nickel at a different molar ratio at the same calcining temperature of 250, and the electrochemical test was carried out. The results showed that the different ratios of nickel and cobalt had a great effect on the capacitance. When the ratio of cobalt and nickel is 2:1, the performance of the material is best. Finally, the electrochemical performance of the sample material after the composite is compared with the single nickel oxide and cobalt oxide synthesized under the same condition. The results show that the electrochemical performance of the composite catalyst has been greatly improved and the stability test results are carried out. It is also shown that after a 3000 ring cycle of 10 A g~ (-1), the specific capacitance attenuates only 7.7% and shows excellent stability. This shows that in the preparation process of hot and high temperature calcination, the composite of nickel and cobalt two greatly improves the capacitance of the material. Third, in order to further improve the electrochemistry of nickel cobalt hydroxide. Properties, we physically compounded the synthesized nickel cobalt hydroxide with MWCNTs, and explored the compound ratio of the two. The two groups were mixed according to the different mass ratio. The results of electrochemical testing showed that the effect was best when the compound ratio was 9:1, and the current density of 1 A g~ (-1) in the KOH electrolyte solution of 1mol L-1. The specific capacitance is up to 1675 F g~ (-1), and the comparison with the composite before the composite shows that the specific capacitance is greatly improved. It shows that the composite of the tubular structure of MWCNTs with the lamellar structure of nickel cobalt hydroxide greatly improves the conductivity of the material and makes the capacitance performance of the material be further improved. The stability test of the material is carried out. It shows that after 3000 cycles, the capacitance retention rate is still 93.2%, showing a good stability.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM53

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