| Titanium-hydrogen system has attracted widespread attention for many years,but many studies are focused on the experiment at home and abroad,only a few of theoretical research focused on the titanium-hydrogen system.Titanium,titanium oxide and the interaction between hydrogen atom is still not clear,nor suited to titanium hydrogen storage film dynamics equations(used for characterization of putting hydrogen absorption time life).Therefore,in order to study the mechanism and mechanism of the absorption and removal of hydrogen from titanium,the mechanism of the resistance of titanium oxide to the absorption and removal of hydrogen from titanium,and the kinetic equation applicable to the hydrogen storage film of titanium were derived.In this paper,the specific process of absorption and dehydrogenation of titanium,the specific process of absorption and dehydrogenation of titanium oxide and the energy change of titanium oxide are studied by using density functional theory.Based on the results of mechanism study,a kinetic model suitable for hydrogen storage thin films of titanium is established,which can be used to predict the hydrogen absorption and desorption time,namely the life.The main contents of the paper include:(1)The surface characteristics,hydrogen absorption process and mechanism of clean Ti were systematically studied.The results showed that H2 molecule is mainly physically adsorbed on the surface of metal Ti,and the optimal adsorption position of H atom on the surface of metal Ti is the surface Hcp bit.During the adsorption of H2 by Ti,the energy barrier needed to be overcome for H2 dissociation is 0.3735eV,and the diffusion energy barrier of H atom on the surface of Ti is 0.223eV.However,when H atom diffuses from the surface to the body,it needs to overcome a high energy barrier,which is significantly higher than that of H2 dissociation and the diffusion potential barrier on the surface of H atom.Therefore,when Ti absorbs hydrogen,the control step is internal diffusion.When H diffuses in Ti,it tends to occupy tetrahedral positions.In addition,the high dissociation energy(1.702ev)of H2 on titanium hydride is the main reason for the reduction of hydrogen absorption rate in the later stage of hydrogen absorption by titanium;(2)The adsorption,dissociation,infiltration,diffusion and other behaviors of H on rutile type TiO2 generated by oxidation of Ti were systematically studied,and the results showed that the first reason for limiting hydrogen absorption is the lack of adsorption sites on the surface of TiO2 and the extremely low adsorption energy of H atom and H2 molecule on the oxide surface;The dissociation energy of H2 on the surface of TiO2 is 2.612eV,which is much higher than that of H2 on the surface of pure Ti.The high dissociation energy of H2 on the surface of TiO2 is the second reason to limit its hydrogen absorption performance.The diffusion energy barrier of H atom on the surface of TiO2 is 2.694eV,and that in the oxide body is 2.095eV.The high diffusion energy barrier is the third reason to limit its hydrogen absorption performance.Based on the theoretical research results,this paper puts forward some optimization suggestions for the prevention of oxidation of Ti and the reprocessing after oxidation;(3)Put on the surface of clean TiH2 behavior process and mechanism of hydrogen,the results showed that the early stage of the hydrogen,due to the surface of TiH2,Ti and H atoms strong ionic bonding effect,lead to the H atoms on the surface of TiH2 combined into H2 can escape to overcome high barrier(2.667eV),which is a major speed put hydrogen early steps.However,it is considered that with the process of hydrogen dehydrogenation,it will soon enter the middle and late stage.At this point,the energy barrier to be overcome by the diffusion of H atom from the body of TiH2 to the surface of TiH2 is 1.113?1.94eV.At this point,internal diffusion is the control step of the whole process of hydrogen dehydrogenation;(4)In view of the current situation that the research on dynamic behavior mainly focuses on three-dimensional alloy spheres and seldom focuses on two-dimensional thin film materials,this paper based on the results of the mechanism research on Ti hydrogen absorption and desorption,obtains the data such as speed limiting steps and energy,and constructs the absorption and desorption kinetic equation suitable for titanium hydrogen storage thin film.This equation can be used to calculate the hydrogen absorption and desorption time(life)of titanium hydrogen storage films.Finally the change of hydrogen absorption and desorption performance under different temperature and pressure is discussed.To sum up,this paper,the whole process of hydrogen with Ti suction has carried on the theoretical research,the Ti put hydrogen absorption mechanism,the restrictive step of detailed research process and result are given,and the effect from the mechanism of surface oxide explanations are given,finally the mechanism of using the results of the study are given for titanium hydrogen storage film dynamics equation is used to represent life.This paper constructs a relatively complete theoretical system for hydrogen storage materials,which can provide data and theoretical support for relevant experiments,reduce the amount of experiments,and provide an idea and method for the optimization of other hydrogen storage materials. |
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