黑磷的表面改性和CO吸附的理论研究

发布时间：2018-06-28 03:42

本文选题：黑磷 + Co原子　；参考：《东南大学》2017年硕士论文

【摘要】：新型二维材料黑磷的成功制备极大地激发了人们对它的研究兴趣,除了与石墨烯,过渡金属硫化物同样具有较高的表面积-体积比之外,黑磷还具有其他优异的性质,例如可观的直接带隙,高的空穴迁移率,高的开关比以及独特的各向异性。这些特点使黑磷成为二维材料领域的研究焦点,甚至有人预测黑磷可能会像石墨烯一样,替代硅成为新一代的半导体材料。本文采用了基于密度泛函理论的VASP(ViennaAb-initio Simulation Package)软件包,对二维材料黑磷的结构及相关性质进行了计算和分析。由于黑磷材料在气体吸附方面表现出不稳定的物理吸附特性,我们选取的主要方法是对单层黑磷进行掺杂和缺陷构建,从而提高黑磷表面的活性,加强黑磷对一氧化碳气体(CO)的吸附程度,最终提高传感的灵敏度。论文主要研究了金属原子掺杂黑磷的电子性质和金属原子掺杂对CO气体吸附的影响。具体的研究内容包括以下几个部分:(1)对Co-BP-CO和BP-CO的电子性质进行了研究分析,通过黑磷表面钴原子(Co)掺杂的改性,发现Co-BP在吸附CO分子后能带结构从直接带隙转变为间接带隙,杂质Co原子和CO分子的轨道耦合也证实了杂质Co原子对CO吸附的促进作用。相比BP-CO结构,Co-BP-CO结构的结合能更大,稳定性更高,而且根据Bader电荷分析,CO气体向Co掺杂黑磷体系转移的电荷数量远远大于纯净黑磷,证明了 Co掺杂提高了黑磷对CO气体的灵敏度和选择性。(2)Co掺杂证明了金属原子在黑磷表面改性方面有很强的积极作用。计算金属掺杂黑磷结构后,我们发现碱金属掺杂会改变黑磷的光学性质,加强电子结构的可调性;贵金属Pd,Pt掺杂黑磷会产生很强的SMSI效应,有助于提高该材料的催化性能;铁磁性金属掺杂黑磷都表现出较强的结合能,而且Fe和Ni杂质还会使黑磷具有磁性;Pb掺杂黑磷表现出很强的金属性质,可以通过外界电场来调节材料的电学特性。在CO吸附方面,Li-BP-CO和Al-BP-CO的能带结构从间接带隙变为直接带隙,而Pd-BP-CO、Pt-BP-CO、Ni-BP-CO和Al-BP-CO则表现出较强的稳定性,Au、Pt、Ni和Al掺杂结构与CO之间存在大量的转移电荷,证明了金属杂质提高了黑磷对CO气体的吸附和探测能力。(3)考虑到实际制备黑磷的过程中会产生缺陷,因此根据不同缺陷位置的排列组合,我们建立了不重复的6种双空位缺陷结构D1-2、D1-3、D1-4、D1-5、D1-6和D1-8。计算发现双空位缺陷黑磷的形成能都小于单空位缺陷,说明双空位缺陷结构更加稳定。缺陷点位置的变化导致P-P成键发生改变,间接影响了黑磷的物理性质和电学性质。结果表明当第一个P原子被移除后,第二个P原子更加容易脱离黑磷。另外,基于缺陷结构的分析,我们提高Co原子在黑磷中的掺杂比例,并得到了最稳定的Co掺杂双空位缺陷黑磷结构,结论证明了增加Co掺杂原子可以大大提高CO的吸附程度,并且能带间隙会随着CO分子吸附数量增加而迅速减小,形成从半导体性质向金属性质过渡的趋势。
[Abstract]:The successful preparation of a new two-dimensional material of black phosphorus has greatly stimulated interest in its research. In addition to the high surface area volume ratio of the transition metal sulfide, the black phosphorus also has other excellent properties, such as considerable direct band gap, high hole mobility, high switching ratio and unique anisotropy. These characteristics make black phosphorus a focus in the field of two-dimensional material, and even some people predict that black phosphorus may be like graphene, instead of silicon to become a new generation of semiconductor materials. In this paper, the VASP (ViennaAb-initio Simulation Package) soft package based on density functional theory (DFT) is used for the structure and related properties of black phosphorus in two-dimensional material. The calculation and analysis are carried out. Because of the unstable physical adsorption characteristics of the black phosphorus material in the gas adsorption, the main method is to doping and constructing the single layer black phosphorus, thus improving the activity of the surface of the black phosphorus, strengthening the adsorption degree of the black phosphorus to the carbon monoxide gas (CO), and finally improving the sensitivity of the sensor. The effects of the electronic properties of the metal atom doped black phosphorus and the doping of metal atoms on the adsorption of CO gas are mainly studied. The specific research contents include the following parts: (1) the electronic properties of Co-BP-CO and BP-CO are studied and analyzed. Through the modification of the cobalt (Co) doping on the surface of the black phosphorus, it is found that Co-BP can bind after the adsorption of CO molecules. From the direct band gap to the indirect band gap, the orbital coupling of the impurity Co atom and the CO molecule also confirms the promotion of the impurity Co atom on the CO adsorption. Compared with the BP-CO structure, the binding energy of the Co-BP-CO structure is larger and the stability is higher, and the charge number of CO gas transferred from the Bader charge to the Co doped black phosphorus system is far greater than that of the pure BP-CO. The net black phosphorus showed that Co doping increased the sensitivity and selectivity of black phosphorus to CO gas. (2) Co doping proved that the metal atoms have a strong positive effect on the surface modification of black phosphorus. After calculating the structure of the doped black phosphorus, we found that the alkali metal doping will change the optical properties of the black phosphorus and strengthen the tunability of the electronic structure; the precious metal Pd, P T doped black phosphorus can produce a strong SMSI effect, which helps to improve the catalytic performance of the material. The ferromagnetic metal doped black phosphorus exhibits strong binding energy, and Fe and Ni impurities will also make the black phosphorus magnetic; Pb doped black phosphorus shows a strong metal property and can adjust the electrical properties of the material through the external electric field. Adsorption on CO On the other hand, the band structure of Li-BP-CO and Al-BP-CO turns from indirect band gap to direct band gap, while Pd-BP-CO, Pt-BP-CO, Ni-BP-CO and Al-BP-CO show strong stability. There is a large amount of transfer charge between Au, Pt, Ni and Al doping structure and CO. It is proved that the metal impurity increases the adsorption and detection ability of black phosphorus to CO gas. (3) considering the reality There will be defects in the process of preparing black phosphorus. Therefore, according to the arrangement and combination of different defect positions, we have established 6 kinds of double vacancy defect structures, D1-2, D1-3, D1-4, D1-5, D1-6 and D1-8., to find that the formation energy of the black phosphorus in the double vacancy defect is less than the single vacancy defect, indicating that the structure of the double vacancy defect is more stable. The changes in the P-P bond change, which indirectly affect the physical and electrical properties of the black phosphorus. The results show that the second P atoms are more easily separated from the black phosphorus when the first P atom is removed. Furthermore, based on the analysis of the defect structure, we improve the proportion of Co atoms in the black phosphorus, and get the most stable Co doped double space. It is proved that the increase of Co doping can greatly increase the adsorption degree of CO, and the energy band gap will rapidly decrease with the increase of the adsorption number of CO molecules, forming a transition from semiconductor properties to metal properties.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.62;O647.3

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