| Hydrogen energy is recognized as an environmentally friendly energy source,it has the characteristics of highly efficient and reversible.It is expected to replace fossil fuels as a new type of green and sustainable energy in the 21 st century.For the application of hydrogen energy in different fields,hydrogen storage materials should have good hydrogen storage performance and large mass and volume density at ambient condition,the hydrogen storage process should be reversible.Two-dimensional materials are being widely studied as a medium for hydrogen storage,because these two-dimensional structures have a large surface volume ratio,providing a promising way for the development of the next generation of hydrogen storage media.Two-dimensional germanium selenide has become an important material in the growing family of two-dimensional materials.Its abundant reserves,environmental friendliness and excellent photoelectric properties make GeSe particularly attractive in the field of semiconductor applications.In this paper,hydrogen storage performance modulation of hydrogen molecule on two dimensional germanium selenide(GeSe)modified by alkali metal atom is studied based on first-principles calculation.And the alkali metal atoms on the surface of the two-dimensional GeSe,microscopic structure and electronic properties,alkali metal atoms in the two-dimensional diffusion and drift mechanism,the alkali metal atoms on the surface of the GeSe modified two-dimensional selenide microscopic structure and electronic properties of germanium after adsorption of hydrogen,alkali metal atoms modified two-dimensional selenide hydrogen storage properties of germanium and reversibility is studied,the conclusion is as follows:(1)The microscopic electronic structure of alkali metal atoms on two-dimensional GeSe surface is studied.The binding energy of alkali metal atoms(Li,Na,K)is the highest at the high symmetry adsorption site H1,and the modification is more stable.Li atom has the strongest electrostatic interaction with the two-dimensional germanium selenide atom layer,and the main bonding mode is covalent bond.It is not easy for alkali metal atoms to form clusters on the two-dimensional GeSe surface.Meanwhile,alkali metal atoms tend to diffuse along the zigzag direction of two-dimensional GeSe surface.Moreover,the diffusion barrier of Li,Na and K atoms decreases with the increase of atomic radius.(2)Hydrogen molecular adsorption of alkali metal modified two-dimensional GeSe monatomic layer was studied.The alkali metal GeSe monatomic layer does not readily absorb hydrogen.After modification of two-dimensional GeSe atomic layer by alkali metal,electrostatic interaction between two-dimensional GeSe base modified by alkali metal and hydrogen molecule increases,and hydrogen adsorption increases.Comprehensive analysis of local density of states and part of the state density and found that the hydrogen molecules corresponding state density peak appears in the position of the Fermi level is about 9.5 eV,alkali metal atomic ionization effect of the hydrogen molecules at a lower adsorption,can adsorption in the two-dimensional GeSe surface hydrogen atoms in lithium adsorption on the surface of the modified two-dimensional GeSe base can satisfy the standard of the U.S.department of energy(doe),and can be used for hydrogen storage material.(3)The maximum hydrogen storage capacity of Li atom modified two-dimensional GeSe system was calculated,and its average adsorption energy was-0.12 eV,within the range of the adsorption energy of hydrogen dissociated from the base surface.And the hydrogen adsorption is reversible.The hydrogen storage mass density ratio of 5.529 wt % also exceeded the standard of the us department of energy.The results showed that the two-dimensional GeSe modified by Li atom was a promising hydrogen storage material... |
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