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First-principles Study Of Carbon Nanotubes For Hydrogen Storage

Posted on:2011-03-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y W WangFull Text:PDF
GTID:2131330332963492Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Carbon nanotubes (CNTs) consist of graphene sheets rolled up into a cylindrical shape with a diameter on the nanometer scale. It can be used in many fields for their excellent properties, such as field emission, electrical conductivity, electrochemical systems, hydrogen storage devices and molecular vehicle. The two most promising applicable aspects:One is that it can be used for hydrogen storage materials. The other, some uses CNTs as a superior Li absorption capability. Development of high energy-density power sources is urgently needed in many high-technology applications for solving the problems of environmental pollution and gradual depletion of fossil fuels。From the theoretical point of view, H or Li has the highest energy density. However,at the present state of art, all the commercialized H or Li storage materials do not deliver satisfactory high electrochemical capacity and therefore can not meet the requirements of related high technology applications.Computer Simulation played an important part in the material science. It can be used to study energy storage material.Using first-principles density functional calculations we showed that the strong adsorption between the hydrogen atoms and carbon nanotube surface. We also studide the probable structure of the doped Si-CNTs and B-CNTs and the interaction of doped nanotube with metal atom Li.CASTEP of Material Studio which the first-principles calculations'software based on the density function theory (DFT) are performed in this investigation with the generalized gradient approximation (GGA) by Perdew et al and exchange-correlation functional by Perdewm, Burke and Ernzerhof. CASTEP is consist of generalized gradient approximation (GGA) and Local Density Approximation(LDA).The computer results indicated hydrogen atoms can strongly adsorpt in the surface of the nanotube, Observing impurity state in the Fermi level, hydrogen atom and deformation defect of carbon atoms lead to the change. There are three possible structures for two adsorpt hydrogen atoms. The most stable structure is the doped atoms upon the adjacent carbon atoms. When hydrogen atoms absorbed, asymmetrical deformation can result in impurity state.Density of states about the B or Si atom doped carbon nanotube change slightly.The adsorption of foreign atom effected the electron density. Carbon around the doped atom can effectively accept the electrons.Both B and Si doping increase the lithium atom adsorption in CNTs; the B and Si doping both are form a low electron density region to strengthen Li adsorption in SWNTs. The lower electron density can be in favor of the adsorption. They can transfer the electons from the Li atoms well. While the Si and B-doping forms a highly reactive center for the binding of the Li atom..
Keywords/Search Tags:Carbon nanotubes, Doped atoms, Adsorption Properties, Electronic structure
PDF Full Text Request
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