Design And Research Of Metal-modified Two Dimensional Transition Metal Carbide Hydrogen Storage System

For the common goal of sustainable development,the adoption of clean energy is an important tool.Hydrogen energy is unanimously regarded as the most ideal clean energy because of its clean and high-efficiency characteristics.However,the use of gaseous hydrogen has been limited by storage problems in daily life.The high-pressure gaseous hydrogen storage method has low safety performance and low content.The ultra-low temperature liquid hydrogen storage method requires harsh conditions and high costs.Both hydrogen storage methods are not suitable for daily life,and solid hydrogen storage has relatively low technical requirements,high safety,and high density,making it an ideal hydrogen storage method.Because of the large specific surface area,two-dimensional materials have been used as the main force in solid hydrogen storage materials.This paper uses MXenes(Ti₂C),which has a similar structure to graphene.The active Ti atoms have a strong adsorption effect on hydrogen on its surface,and it is a very good substrate material for hydrogen storage.However,the strong adsorption causes H₂ to dissociate into two H atoms occupying more surface and it is difficult to release.In order to improve the hydrogen storage performance of Ti₂C,the influence of different metals on Ti₂C hydrogen storage is mainly studied,and the high-density hydrogen storage materials are designed by means of high-concentration doping.The main research contents of this paper are as follows:1.Using first principles,the hydrogen storage performance and mechanism of intrinsic two-dimensional transition metal carbide(Ti₂C)are studied.The establishment of the model and calculation methods are introduced in detail,the geometric structure and adsorption energy of different amounts of H₂ adsorption are studied,and the H₂ adsorption mechanism is studied through charge layout and PDOS,which pave the way for the hydrogen storage performance of metal modified Ti₂C.2.To study the effect of a single metal modified Ti₂C on hydrogen adsorption.This paper specifically studied the structure and quantity of hydrogen adsorbed by Ti₂C under the modification of alkali metals(Li,Na,K),transition metals(Sc)and rare earth metals(La),and the adsorption energy,and through the charge layout,differential charge density.The diagram analyzes the adsorption mechanism.The study found that the metal acts as a bridge in the entire adsorption process,which reduces the activity of Ti atoms on the Ti₂C surface.By comparison,it is found that Li atoms are the most significant in improving the hydrogen storage characteristics of Ti₂C,allowing hydrogen to be adsorbed around metal atoms in the form of molecules.The maximum adsorbable ten hydrogen mass density is 4.33wt%,and the adsorption energy is-0.26e V/H₂.It is easy to release,its doping modification is suitable for hydrogen storage,laying the foundation for the following design of high-density hydrogen storage materials.3.Based on the intrinsic properties and the hydrogen storage performance and mechanism of Ti₂C modified by metal,a number of high-density hydrogen storage materials with Li modified Ti₂C were designed,and the hydrogen storage capacity was 6.21wt%.The diffusion barrier is obtained by the transition state search(TS)method to study the diffusion behavior of Li atoms to determine the stability of Li on the surface and whether agglomeration occurs.Using vertical,inclined and parallel H₂ to the base material to find the best adsorption structure,the adsorption energy of different numbers of hydrogen molecules was calculated.In addition,molecular dynamics was used to simulate the thermodynamic stability of medium.Finally,the hydrogen storage properties of hydrogen storage media at different temperatures and pressures are calculated,and the grand canonical ensemble is used to quantify the amount of hydrogen adsorption at different pressures and temperatures.