| With the continuous development of economy and society,the use of fossil energy is increasing,which leads to a great threat to people's living environment.More and more people are paying attention to hydrogen because it is pollution-free and a renewable energy source.Therefore,suitable hydrogen storage materials should be sought.In recent years,researchers have focused on hydrogen storage methods for two-dimensional materials.Among them,boron silide has excellent properties.At the same time,researchers recently discovered a new type of graphene that is even better at storing hydrogen.Si3C,as a new two-dimensional material,also has good hydrogen storage performance.In this paper,the hydrogen storage processes and principles of SiB,?-2 Graphyne and Si3C are studied by combining first principles.Mainly from the following points:(1)The optimal adsorption site of Li on the surface of SiB is located just above the center of the six-member carbon ring of SiB structure.Finally,eight Li atoms are modified on the SiB structure.Since the average binding energy of Li atoms is greater than its cohesion energy,it indicates that there is no clustering phenomenon and stable adsorption on the surface of SiB material.Through differential charge analysis,it can be seen that charge transfer occurs between the two materials,thus forming local electrostatic field,so Li can be stably distributed on the surface of SiB.Then,hydrogen molecules were added until the maximum value was reached,and the adsorption energy of hydrogen molecules was calculated to be 0.21 e V/H2,with a mass ratio of 8.69 wt%.(2)doping the structure with B atom to enhance its hydrogen storage capacity.The hydrogen storage properties of?-2 Graphyne doped with B atoms modified by alkali metals Li and Na and transition metals Ti,V and Sc were studied based on first principles calculations.The selection of the best adsorption sites for these six metal atoms is analyzed in detail.In the hydrogen adsorption structure,the average adsorption energy of?-2 Graphyne structure modified by Li atom and Na atom is 0.21e V/H2 and 0.18 V/H2,respectively,and the mass ratio of hydrogen storage is 14.8wt%and 5.30 wt%,respectively.The average adsorption energies of 2B-?-2 Graphyne structure modified by Ti,V and Sc atoms are 0.31 e V/H2,0.42 V/H2 and 0.25 e V/H2,respectively,and the mass ratios of hydrogen storage are 5.61 wt%?5.53 wt%and 5.70 wt%,respectively.(3)Based on Si3C material,we modified the structure with Li atom to improve the hydrogen storage capacity.The optimum adsorption site of Li atom is just above the center of Si3C Si-membered silicon ring.This structure can adsorb up to eight Li atoms.There were no clusters.In the hydrogen storage process of 8Li-Si3C structure,the maximum capacity of each Li atom hydrogen molecule is four hydrogen molecules,the average adsorption energy is 0.21 e V/H2,and the mass ratio of hydrogen storage is 13.6 wt%. |
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