B、N共掺杂石墨烯电子结构和共掺杂表面吸附性能的第一性原理研究

发布时间：2018-04-09 01:00

本文选题：第一性原理　切入点：石墨烯　出处：《太原理工大学》2017年硕士论文

【摘要】：实验中已经证明石墨烯用作为电极材料具有很高的比容量,而且N和B掺杂的石墨烯对里空气电池中的氧还原有很好的催化作用,所以掺杂石墨烯作为具有催化性能的电极材料而广泛的应用锂空气电池中。本文采用第一性原理的研究方法,对不同晶胞类型的单层石墨烯进行硼、氮以邻、间、对位三种相对位置共掺杂,并对共掺杂石墨烯的电子结构和锂原子及氧气Li、O2在掺杂表面的吸附性能做了详细研究。主要研究结论如下:(1)B、N以邻、间、对三种相对位置共掺杂不同晶胞类型石墨烯,石墨烯的能带出现带隙,价带最高点和导带最低点都出现在布里渊区的同一点,带隙属于直接带隙,而且价带和导带的能带分布更靠近费米能级。间位共掺杂结构的带隙均小于邻位和对位,而具有最好的导电性能。(2)由于B、C、N三种元素电负性的差异,共掺杂结构的电子重新分布,其中间位结构中各原子的电荷转移量均小于邻位和对位。B、C、N原子间发生杂化,而且杂化主要发生在各原子的2p轨道,其中B-C原子杂化轨道的能量状态较高更靠近费米能级,C-N原子杂化轨道分布在能量较低的区域。(3)B、N原子共掺杂破坏了石墨烯结构中的π电子对,活化了石墨烯的表面。与石墨烯相比B、N掺杂表面为锂提供更稳定的吸附位点,氧气在掺杂表面的吸附能也增加,但仍属于物理吸附。
[Abstract]:It has been proved that graphene has high specific capacity as electrode material, and that N and B doped graphene can catalyze oxygen reduction in internal air batteries.Therefore, the doped graphene has been widely used in lithium air batteries as an electrode material with catalytic properties.In this paper, boron, nitrogen, para-position and boron were co-doped in three monolayer graphene monolayers with different unit cell types by first-principles method.The electronic structure of co-doped graphene and the adsorbability of lithium atom and oxygen Li-O _ 2 on the doped surface were studied in detail.The main conclusions are as follows: (1) the energy band gap of graphene, the highest point of valence band and the lowest point of conduction band of graphene are found at the same point in Brillouin region.The band gap belongs to the direct band gap, and the band distribution of valence band and conduction band is closer to Fermi energy level.The band gap of the mesopotopic co-doped structure is smaller than that of the adjacent and opposite sites, but it has the best conductivity. 2) due to the difference of the electronegativity of the three elements, the electron redistribution of the co-doped structure is observed.The charge transfer amount of each atom in its intermediate structure is smaller than that between adjoining and para-position. The hybridization occurs mainly in the 2p orbitals of each atom.The higher energy state of B-C atom hybrid orbital is closer to the Fermi energy level C-N atom hybrid orbital distribution in the lower energy region. The 蟺 electron pair in graphene structure is destroyed by co-doping of BN atom and the surface of graphene is activated.Compared with graphene, the BN doped surface provides a more stable adsorption site for lithium, and the adsorption energy of oxygen on the doped surface also increases, but still belongs to physical adsorption.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71;O647.3

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