First-principles Study On The Hydrogen Storage Properties Of Transition Metal Modified Vacancies Graphene

Hydrogen fuel cell vehicles(HFCs) are new energy vehicles attracting more attention after pure electric vehicles.The lack of capacity of hydrogen storage in the conventional hydropower storage way restricts the development of hydrogen fuel cell vehicles,and the exploration of new hydrogen storage materials with reduced voltage,room temperature and large production capacity is an immediate issue to be fixed.An increasing array of studies discovered have discovered that graphene have the potential to attract hydrogen,and after modification with defects or metals,which can significantly increase their hydrogen storage abilities.In the work,the hydrogen storing ability of transition metal modified single defect(SVG)and double defect(DVG-N(N=1-5))was investigated systematically and thoroughly using first principles.The present paper’s principal investigation and conclusions are as under.(1)First principles method was used to establish SVG and DVG-N(N=1-5)models with excessive metal modification,structural improvements were made to obtain the generation of energy,and DVG-4 structure with the highest formation energy was obtained.Ti,Sc and Y transition metals were selected as modification atoms,and the structural flexibility is best when the transition metal is in the middle of the defect;the morphological properties of X-SVG and X-DVG-4 were investigated,and the fruits indicate that the introduction of Ti,Sc and Y can enhance the compression performance of hydrogen storage structures in different directions and the anti-shear deformation ability between layers,and prolong the life of hydrogen storage system.(2)The optical characteristics of X-SVG and X-DVG-4 were investigated.The outcome demonstrates that the electron polarization and shielding effect are reduced in the structure.As the quantity of chargecarriers grows with frequency,the absorption of available energy in the low frequency range decreases,the absorption of observable light with photon energies between2 eV and 6 eV increases.The blue shift of the transition metal energy loss function increases the resonance frequency of atomic energy.X-SVG,X-DVG-4 hydrogen storage system to introduce solar energy can improve the capacity of hydrogen discharge.(3)The hydrogen absorption performance of X-SVG and X-DVG-4 materials was explored.The adsorption energy of intrinsic graphene on hydrogen molecules is all less than0.1eV,far less than 0.2eV,and its sorption is weakly physisorbed.The Al modified Si-doped graphene(SLG+Si+Al)energy of attract is between 0.2eV and 0.6eV,and its mass percentage of residual hydrogen is 2.68 wt%.And the defective DVG-4 structure is 5.97wt%.The adsorption energy of SVG and DVG-4 system modified by transition metal for hydrogen adsorption is the same as that of SLG+Si+Al,which is within the range of reversible adsorption,The hydrogen storage capacity of X-SVG(Sc、Y、Ti)was 1.87wt%,2.04 wt% and 1.56wt%,respectively,and that of X-DVG-4(Sc、Y、Ti)was 4.06wt%,4.59wt% and 3.47wt%,respectively,which proved that the hydrogen storage stability and density of the transition metal-modified double defect graphene were higher than those of the intrinsic graphene and Sl G +Si+Al.