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First-principles Study of Carbon Nanotubes for Hydrogen Storage

Author: WangYaZuo
Tutor: YinYanSheng
School: Ocean University of China
Course: Materials Physics and Chemistry
Keywords: Carbon nanotubes Adsorption stable bit Dopant atoms Electronic structure Density of states
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 179
Quote: 1
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Abstract


Carbon nanotubes (CNTs) is a hollow cylinder, the diameter of the curl is formed from graphite in the nanometer scale the CNTs have their own unique properties is applied to the field of field emission materials, electronic devices, hydrogen storage media and molecular carrier, wherein most The potential application is used as a hydrogen storage material and save for lithium (Li) of the carrier (H). The development of high energy density chemical power is a key technology to solve a series of major issues of the future transport, environment and resources, the highest energy density system almost all H and Li energy materials. Judging from the current state of development, the existing reservoir H and Li storage material defects with low specific energy can not meet the demand for technology applications. CNTs as hydrogen storage and lithium storage materials can effectively improve the specific energy, by the researchers' attention. The scientific computing Following the theoretical science and experimental science, human understanding and conquering nature third scientific method. Computer simulation technology plays an increasingly important role in the Materials Science and Engineering, a considerable amount of computer simulation methods have been used in the field of energy storage materials research. Calculated using CASTEP software based on first principles of Material Studio, the CASTEP software calculation method based on the density functional theory (DFT) on the basis, including the generalized gradient approximation and local density approximation, this thesis under the generalized gradient approximation Perdewm Burke and Ernzerhof exchange-correlation functional method. By density functional theory first studied the adsorption of a single H atom and two H atoms in the surface of CNTs. The calculation results show that the individual H atoms to form Chemisorption stable exist on the surface of CNTs, its Fermi level at the introduction of the impurity states, is adsorption of H atoms and produce the result of the combined effect of the deformation defects at the C atom; two H atoms in the the CNTs surface of the adsorption is divided into three different configurations, the most stable conformation is two H atoms adsorbed on two adjacent C atoms, such a configuration of its Fermi level at the impurity states. The theoretical analysis of CNTs due to the adsorption of H atoms in the asymmetric deformation are more likely to have impurity states. The paper analyzes the atom of silicon (Si) and boron (B) the doped CNTs performance, and doped single-walled carbon nanotubes adsorbed Li atoms are several possible geometry. Single Si atom and B atom, respectively doped single-walled carbon nanotubes slight effect on the density of states on the CNTs, but reduce the electron density of the dopant atoms of the surrounding area, so that the electron dispersion associated with the C atom to which they are attached. Calculated that the Li atom adsorbed on the doped CNTs reinforced. Electronic structure analysis showed that the dopant atoms surrounding the formation of a low electron density region, the formation of electron-deficient system is conducive to the adsorption of the Li atom; Si and B two dopant atoms can transfer electrons from the Li atom to form an end in itself the Li atom highly active adsorption area.

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