以生物质为源的多孔碳及其复合物的制备以及其电化学性能的研究

发布时间：2018-03-01 18:19

  本文关键词： 超级电容器 电极材料 多孔碳 水溶性壳聚糖 电化学性能　出处：《西北大学》2015年硕士论文　论文类型：学位论文

【摘要】：超级电容器也叫做电化学电容器,由于一般情况下它们的比电容较高、循环稳定性好、工作原理比较容易还有功率密度也比较高等特点而渐渐成为人们关注的热点,同时,它也与二次电池联用而广泛的被科研人员探索。由于极大多数具有高比表面积的多孔碳的电化学性能都非常卓越优良,而且其成本也相对较低,多孔碳材料已渐渐成为科学家们使用最广泛的一种电极材料。而使用过渡金属氧化物与碳材料复合作为电极材料时,会进一步提升其比电容。由于生物质种类众多,含量非常丰富并且成本低廉,属于可再生资源,可以对其进行循环利用和开发。同时,生物质是自然界存在的可再生的碳载体,人们在将其转化为新式的炭材料方向做了很多工作,所以说生物质在制备碳材料方面拥有广阔的发展空间。最近,多孔碳材料的制备很多都是使用生物质为原材料,这渐渐变成了一个热门的研究课题,利用生物质作为原料,不仅可以节约成本,而且可以减削由大量废弃生物质焚烧给环境带来的污染问题。生物质的种类多种多样,而壳聚糖是自然界含量除了纤维素以外含量最高的多糖。除了壳聚糖以外,莲蓬壳也是一种重要的生物质,莲蓬壳除了少部分入药以外,大部分被丢弃成为垃圾或作为低热值燃料,造成了巨大的能源浪费。本文的工作是选用水溶性的壳聚糖以及莲蓬壳分别为碳源,通过碳化最后得到了多孔碳基电容器电极材料,实验内容主要为：(1)采用直接水热碳化水溶性壳聚糖得到片状碳材料的中间体,并进一步对得到的产物进行高温碳化,得到片状多孔碳材料。结果表明：通过在800℃下碳化后得到的多孔碳材料的比电容为166 F/g,在2000次循环后其比容量约为之前的98%。(2)采用水热发通过原位复合得到了碳/Fe3O4复合物,并进一步对得到的产物进行高温碳化,得到了碳与过渡金属氧化物的复合材料。结果表明,在0.05 A g-1的电流密度下,多孔碳/Fe3O4的比电容可达到299 F g-1,当电流密度增大为2 A g-1后,比电容下降了20.7%。多孔碳/Fe3O4具有良好的充放电循环稳定性,在循环2000次后它的比容量仍保持之前的84%。(3)以莲蓬壳为原料,KOH为活化剂,采用碳化活化两步方法来制备以生物质为源的碳材料。此外,我们还探讨了加入KOH的量和活化温度对产物的比表面积和比容量的影响。我们发现：当活化剂与莲蓬壳的质量比为4：1时,样品的比表面积达到最大(2961m2g-1),0.5Ag-1电流密度下的比容量可达345 F g-1。另外,我们在工作中还研究了不同活化温度和不同活化剂用量对产物以及其电化学性能的影响。
[Abstract]:Supercapacitors, also called electrochemical capacitors, have become the focus of attention because of their high specific capacitance, good cycle stability, easy working principle and high power density. It has also been extensively explored by researchers in conjunction with secondary batteries. Because most of the porous carbon with high specific surface areas has excellent electrochemical performance and its cost is relatively low, Porous carbon materials have gradually become the most widely used electrode materials by scientists. When the transition metal oxides and carbon materials are used as electrode materials, the specific capacitance is further enhanced. Rich in content and low in cost, it is a renewable resource that can be recycled and exploited. At the same time, biomass is a renewable carbon carrier that exists in nature. A lot of work has been done to turn it into new carbon materials, so biomass has a lot of room for development in the preparation of carbon materials. Recently, many porous carbon materials have been prepared using biomass as raw materials. This has gradually become a hot research topic. Using biomass as raw material can not only save costs, but also reduce the pollution caused by the incineration of a large amount of waste biomass. There are many kinds of biomass. In addition to chitosan, the shell of lotus is also an important biomass. Most of them were discarded as garbage or as low calorific value fuel, which resulted in a huge waste of energy. In this paper, water-soluble chitosan and lotus shell were selected as carbon source, and the porous carbon capacitor electrode materials were obtained by carbonization. The main content of the experiment is: (1) the intermediate of flake carbon material is obtained by direct hydrothermal carbonization of water-soluble chitosan, and the obtained products are further carbonized at high temperature. The results show that the specific capacitance of the porous carbon materials obtained by carbonization at 800 鈩，

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