Theoretical Research On The Regulation Of The Electronic Structure Of Graphyne And Its Gas Adsorption Properties

The massive consumption of fossil fuels has led to energy shortages and various environmental problems such as global warming and severe air pollution,making the search for cleaner energy sources to replace traditional fossil fuels an urgent priority.Natural gas and hydrogen,which are mainly composed of methane（CH₄）,present great opportunities and challenges,especially in the area of clean energy vehicles.The gaseous nature still poses technical challenges for the safe operation and efficient storage of on-board CH₄ and hydrogen.It has been found that storage of CH₄ and H₂in porous materials is a safe and efficient storage method due to their good adsorption properties and lighter mass.Graphyne combine the advantages of molecular sieves and MOF materials for gas storage,with large specific surface area and regular pore structure as well as sp and sp² hybridization for alkyne bond formation,showing significant advantages in gas adsorption and storage.In this study,the CH₄ molecular adsorption properties and hydrogen storage properties of metal-atom modified 6,6,12-graphyne alkynes are investigated based on giant regular Monte Carlo simulations and density flooding theory studies.According to giant canonical Monte Carlo,the CH₄ adsorption of Sc modified6,6,12-graphyne can reach 72.21 wt.%at 233 K,40bar.A first-principles study revealed that the most stable modification site for Sc atoms on 6,6,12-graphyne systems is the central pore site of the rhombic acetylene ring,embedded in the plane where the d orbital of the Sc atom can form a strong hybridization with the p orbital of the C atom in 6,6,12-graphyne with a binding energy of-5.181 e V on both sides,its average adsorption energy is-0.178 e V,and the adsorption capacity is as high as 72.13 wt.%,exceeding the Department of Energy standard（50 wt.%）,which confirms each other with the results of the giant canonical Monte Carlo simulation,and verifies the accuracy of the results.Sc modified 6,6,12-graphyne bifaces can adsorb up to 42.Study of the hydrogen storage properties of metal-modified 6,6,12-graphyne.The unembedded Na atoms are more favourable for the adsorption of H₂ molecules than the Sc and Ca modifications,and the two Na atoms prefer to be modified on either side of the rhombic macropore site of 6,6,12-graphyne with an average binding energy of-2.357 e V,which is greater than its cohesion energy and less prone to metal agglomeration.interaction and both generate an electric field.The adsorption of H₂ at temperatures ranging from 77 K,233 K and 298 K and pressures ranging from 1 to 100bar was simulated using GCMC and the Na-modified 6,6,12-graphyne was found to have a hydrogen storage capacity of 16.16 wt.%at 77 K and 100bar.First principles calculations show that Na modified 6,6,12-graphyne can adsorb 13 pairs of H₂molecules on both sides with an average adsorption energy of-0.102 e V and a high adsorption capacity of 16.55 wt.%,which far exceeds the Department of Energy standard.The above studies show that the modified 6,6,12-graphyne system with metal atoms has good CH₄ and H₂ storage properties and that 6,6,12-graphyne is a high-capacity CH₄ and H₂ storage material.