石墨烯电容去离子性能的原子及电子层次理论模拟
发布时间：2018-09-06 10:19
【摘要】：随着社会重工业技术高速发展和人们需求的不断提升,工业污水和生活污水对有限的可用的淡水资源造成严重污染,从大量的海水中获取经济实惠的淡水资源成为了众多学者关注的焦点。目前海水淡化技术中蒸馏、电渗析,反渗透和离子交换等方法存在各自的缺点。电容去离子技术实现低能耗无污染成为可能。石墨烯具有较高的比表面积和良好的电导率等优点,吸引众多学者利用其进行电容去离子技术研究,但是目前对其除盐的理论研究较少。本文利用模拟计算的方法对其电容性能和脱盐性能进行研究。运用分子动力学模拟方法(LAMMPS)和密度泛函理论(CASTEP)计算了本征石墨烯的界面电容,通过对本征石墨烯电极施加电荷来模拟充电过程来研究与1-丁基-3-甲基咪唑六氟磷酸盐([BMIM][PF6])离子液体形成的界面电容。结果表明,在?a=±0.6 V时本征石墨烯具有较大的界面电容,约为70 F/g,与实验值基本吻合。运用分子动力学模拟考察了不同操作条件对本征石墨烯电容去离子性能的影响。根据出水口处氯化钠离子和水分子的数量比作为除盐率指标,并通过对电极表面流体流速和离子吸附量等手段探讨了操作条件变化对除盐率的影响。结果表明,增加电极表面电荷密度、减小电极板间距和降低流体流速均提高电容去离子性能。运用分子动力学模拟和密度泛函理论计算了含缺陷石墨烯电极和氮掺杂石墨烯电极的界面电容,计算结果与本征石墨烯比较发现,随着含缺陷量增加界面电容逐渐降低,氮掺杂量增加界面电容逐渐升高,并且当氮掺杂率为4.1%时,具有较大的界面电容,约为122 F/g,与实验值基本符合。以含缺陷石墨烯和氮掺杂石墨烯作为电极,运用分子动力学模拟对两种电极除盐性能进行研究。结果表明,随着含缺陷量的增多,除盐率逐渐降低;氮掺杂量的增多,除盐率逐渐升高。
[Abstract]:With the rapid development of social heavy industry technology and the increasing demand of people, industrial sewage and domestic sewage cause serious pollution to the limited available freshwater resources, It has become the focus of many scholars to obtain economical fresh water resources from a large amount of seawater. At present, the methods of distillation, electrodialysis, reverse osmosis and ion exchange have their own shortcomings in seawater desalination. It is possible to realize low energy consumption and no pollution by capacitive deionization technology. Graphene has many advantages, such as high specific surface area and good conductivity. In this paper, the capacitance and desalination performance are studied by means of simulation calculation. The interfacial capacitance of intrinsic graphene was calculated by molecular dynamics simulation method (LAMMPS) and density functional theory (CASTEP). The interface capacitance formed with 1 Ding Ji 3 methyl imidazolium hexafluorophosphate ([BMIM] [PF6]) ionic liquid was studied by charging the intrinsic graphene electrode to simulate the charging process. The results show that the intrinsic graphene has a large interfacial capacitance of about 70 F / g at a value of 卤0.6 V, which is in good agreement with the experimental value. The effects of different operating conditions on the deionization properties of intrinsic graphene capacitors were investigated by molecular dynamics simulation. According to the quantity ratio of sodium chloride ion and water molecule at outlet as desalination rate, the influence of operation conditions on desalination rate was discussed by means of flow velocity and ion adsorption amount on electrode surface. The results show that increasing the surface charge density of the electrode, decreasing the electrode plate spacing and decreasing the flow rate can improve the performance of capacitance deionization. The interfacial capacitance of graphene electrode containing defects and that of nitrogen-doped graphene electrode is calculated by using molecular dynamics simulation and density functional theory. Compared with the intrinsic graphene electrode, it is found that the interface capacitance decreases with the increase of defect content. When the nitrogen doping ratio is 4.1, the interfacial capacitance is about 122F / g, which is in good agreement with the experimental value. The desalination properties of the two electrodes were studied by molecular dynamics simulation using graphene containing defects and nitrogen-doped graphene as electrodes. The results show that the desalination rate decreases with the increase of the defect content, and the desalination rate increases with the increase of nitrogen doping content.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P747
本文编号：2226050
[Abstract]:With the rapid development of social heavy industry technology and the increasing demand of people, industrial sewage and domestic sewage cause serious pollution to the limited available freshwater resources, It has become the focus of many scholars to obtain economical fresh water resources from a large amount of seawater. At present, the methods of distillation, electrodialysis, reverse osmosis and ion exchange have their own shortcomings in seawater desalination. It is possible to realize low energy consumption and no pollution by capacitive deionization technology. Graphene has many advantages, such as high specific surface area and good conductivity. In this paper, the capacitance and desalination performance are studied by means of simulation calculation. The interfacial capacitance of intrinsic graphene was calculated by molecular dynamics simulation method (LAMMPS) and density functional theory (CASTEP). The interface capacitance formed with 1 Ding Ji 3 methyl imidazolium hexafluorophosphate ([BMIM] [PF6]) ionic liquid was studied by charging the intrinsic graphene electrode to simulate the charging process. The results show that the intrinsic graphene has a large interfacial capacitance of about 70 F / g at a value of 卤0.6 V, which is in good agreement with the experimental value. The effects of different operating conditions on the deionization properties of intrinsic graphene capacitors were investigated by molecular dynamics simulation. According to the quantity ratio of sodium chloride ion and water molecule at outlet as desalination rate, the influence of operation conditions on desalination rate was discussed by means of flow velocity and ion adsorption amount on electrode surface. The results show that increasing the surface charge density of the electrode, decreasing the electrode plate spacing and decreasing the flow rate can improve the performance of capacitance deionization. The interfacial capacitance of graphene electrode containing defects and that of nitrogen-doped graphene electrode is calculated by using molecular dynamics simulation and density functional theory. Compared with the intrinsic graphene electrode, it is found that the interface capacitance decreases with the increase of defect content. When the nitrogen doping ratio is 4.1, the interfacial capacitance is about 122F / g, which is in good agreement with the experimental value. The desalination properties of the two electrodes were studied by molecular dynamics simulation using graphene containing defects and nitrogen-doped graphene as electrodes. The results show that the desalination rate decreases with the increase of the defect content, and the desalination rate increases with the increase of nitrogen doping content.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P747
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