石墨烯储氢性能的第一性原理研究

发布时间：2018-05-03 08:39

本文选题：储氢材料 + 石墨烯　；参考：《昆明理工大学》2017年硕士论文

【摘要】：氢能源是目前最具有开发价值的新型清洁能源,由于氢来源于水,氢能在地球上储量丰富,氢的储能比较高,燃烧产物是水,对环境无污染,是一种环保的可持续清洁能源。近年来,大量的科研学者对氢能源的开发做了大量的研究工作,发现氢的储存和运输是氢能源利用的关键,然而传统的储氢技术和储氢材料由于其储氢量较低,所以并不能满足现阶段我们对氢能源的利用的需求,我们需要开发新的储氢材料。近年来,不少科研学者为寻找安全、耐用的储氢材料做了大量研究,石墨烯的出现为储氢材料的发展提供了新的研究方向。石墨烯是近几年来发现的一种二维石墨结构材料,具有很多优异的性质,具有较大的比表面积以及超高的强度,适合用来制备储氢材料。然而,纯石墨烯的储氢量较低,需要对石墨烯进行改性处理,通过大量的研究发现,石墨烯材料经过掺杂修饰、缺陷等改性处理之后,大幅度提高了石墨烯与氢分子的结合能,是一种有研究价值的储氢材料。基于上述研究背景,本文通过基于密度泛函理论的第一性原理计算,系统研究了金属元素铝和钙修饰石墨烯对其储氢性能的影响;由于实际生产中制备出的石墨烯或多或少的含有缺陷,我们对缺陷石墨烯吸附氢分子的模型进行了计算,为实验中制备石墨烯储氢材料提供了理论依据。A1原子修饰的石墨烯对氢分子的吸附形式主要是物理吸附,其中每个铝原子最多能吸附6个氢分子,而且吸附能在-0.2eV——0.6eV/H2之间,此时石墨烯具有很好的可逆储氢能力,说明铝修饰石墨烯是一种很有潜力的储氢材料。Ca修饰的石墨烯有良好的储氢能力,其中Ca修饰石墨烯对氢分子的吸附主要是物理吸附,也有一部分化学吸附作用,研究表明,钙修饰石墨烯吸附氢分子时,当氢分子密度高时,出现氢分子溢出现象,其中每个钙原子周围吸附4个氢分子时,吸附能最低,也就是说吸附4个氢分子时的结构最稳定,当吸附4个以上氢分子时,部分氢分子分解成氢原子,钙修饰石墨烯的平均吸附能的绝对值过大,不利于氢分子的释放。含有缺陷的石墨烯能一定程度的提高石墨烯的储氢能力,其对氢分子的吸附既有物理吸附也有化学吸附,其中以物理吸附为主,含有双控位缺陷的石墨烯比单空位缺陷石墨烯具有更大的氢分子平均吸附能,双控位缺陷的石墨烯比单空位缺陷石墨烯具有更好的储氢能力。
[Abstract]:Hydrogen energy is a new type of clean energy which has the most development value at present. Because hydrogen comes from water, hydrogen energy is abundant on earth, hydrogen energy storage is relatively high, combustion product is water, no pollution to the environment, it is a kind of sustainable clean energy of environmental protection. In recent years, a large number of researchers have done a lot of research work on the development of hydrogen energy. It is found that the storage and transportation of hydrogen is the key to the utilization of hydrogen energy. However, the traditional hydrogen storage technology and hydrogen storage materials are relatively low due to their hydrogen storage capacity. Therefore, we do not meet the current demand for hydrogen energy use, we need to develop new hydrogen storage materials. In recent years, many researchers have done a lot of research to find safe and durable hydrogen storage materials. The appearance of graphene provides a new research direction for the development of hydrogen storage materials. Graphene is a two-dimensional graphite structure material found in recent years. It has many excellent properties, large specific surface area and super high strength, so it is suitable for the preparation of hydrogen storage materials. However, the hydrogen storage capacity of pure graphene is relatively low, so it is necessary to modify graphene. Through a large number of studies, it is found that the binding energy of graphene and hydrogen molecules is greatly improved after the modification of graphene materials through doping modification, defects and other modification treatments. It is a valuable hydrogen storage material. Based on the above research background, the effects of metal elements aluminum and calcium modified graphene on hydrogen storage properties were systematically studied by first-principle calculation based on density functional theory. Because the graphene produced in actual production contains more or less defects, we have calculated the model for the adsorption of hydrogen molecules by graphene. It provides a theoretical basis for the preparation of graphene hydrogen storage materials. The adsorption form of graphene modified by Al atom is mainly physical adsorption, in which each aluminum atom can adsorb at most 6 hydrogen molecules, and the adsorption energy is between -0.2 EV and 0.6 EV / H 2, and the adsorption energy is between -0.2eV and 0.6eV / H2, and the adsorption energy is between -0.2eV and 0.6eV / H2. At this time, graphene has a good reversible hydrogen storage ability, which indicates that aluminum-modified graphene is a potential hydrogen storage material. Ca modified graphene has a good hydrogen storage ability, and the adsorption of Ca modified graphene on hydrogen molecules is mainly physical adsorption. There is also some chemisorption. It is shown that when the hydrogen molecules are adsorbed by calcium modified graphene, hydrogen spillovers occur when the density of hydrogen molecules is high, and the adsorption energy is the lowest when 4 hydrogen molecules are adsorbed around each calcium atom. That is to say, the structure of adsorbed four hydrogen molecules is the most stable. When more than four hydrogen molecules are adsorbed, some hydrogen molecules are decomposed into hydrogen atoms, and the average adsorption energy of calcium modified graphene is too large, which is not conducive to the release of hydrogen molecules. Graphene containing defects can improve the hydrogen storage ability of graphene to a certain extent. The average hydrogen adsorption energy of graphene with double position defects is higher than that of graphene with single vacancy defect, and the hydrogen storage capacity of graphene with double control defect is better than that with single vacancy defect.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11

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