A prediction method for physical adsorption hydrogen storage materials

Abstract

The present application discloses a prediction method for a physical adsorption hydrogen storage material, the physical adsorption hydrogen storage material includes a two-dimensional nanomaterial doped with metal atoms, and the prediction method includes the following steps: replacing the hydrogen atom group at the armchair boundary position of the stable material structure with metal atoms in the computer software for atomic scale material simulation, and calculating the binding energy and maximum hydrogen storage weight fraction of the titanium atoms in the material structure doped with metal atoms. The present application predicts a new type of physical adsorption hydrogen storage material, the hydrogen storage weight fraction can reach up to 7.86wt%, and the material itself is only composed of carbon, hydrogen, oxygen, nitrogen and titanium and other very light atoms, which reduces the weight of the hydrogen storage material itself and provides a new option for hydrogen storage and transportation.

Description

Technical Field

[0001] The present application relates to the computational prediction of hydrogen storage performance of an artificially synthesized two-dimensional material, and belongs to the field of physical adsorption hydrogen storage materials. Background Art

[0002] Hydrogen energy has always been regarded as a clean, green and renewable new energy that can replace traditional fossil energy. Hydrogen is abundant on the earth and is easily accessible. At the same time, hydrogen fuel has a very high energy density, up to 142MJ / Kg, which is three times that of traditional fossil fuels. One of the major uses of fossil fuels is automotive fuel, and hydrogen-powered vehicles are also developing rapidly. According to the performance requirements for on-board hydrogen storage materials issued by the U.S. Department of Energy (DOE) in 2020, the hydrogen storage weight fraction of hydrogen-powered vehicles should reach 4.5wt% and eventually reach 6.5wt%; the volume density should reach 30gH 2 / L; the working temperature of hydrogen storage materials is between -40℃ and 60℃; the release pressure of hydrogen is between 0.5-1.2MPa. At present, the technology of industrial hydrogen production is relatively mature, and hydrogen can be produced through methods such as hydrogen production from chemical byproducts, coal gasification, and water electrolysis. However, the current high cost of hydrogen storage and transportation, the difficulty of storing and using on-board hydrogen, and safety issues are all problems that need to be solved in the use of hydrogen energy.

[0003] In recent decades, in order to solve the technical problems of hydrogen storage, people have studied and developed a variety of hydrogen storage methods. According to the environmental conditions of hydrogen storage and the bonding strength between hydrogen and hydrogen storage materials, hydrogen storage methods can be divided into: physical hydrogen storage, chemical hydrogen storage and physical adsorption hydrogen storage. Physical hydrogen storage mainly compresses and liquefies hydrogen by pressurizing and cooling it, and improves the storage efficiency of hydrogen by increasing the storage density of hydrogen. This is also the most commonly used hydrogen storage method. However, it has many disadvantages: first, the storage tanks for compressed gas have great safety hazards. Secondly, the transportation and storage of compressed hydrogen require high costs. Finally, compressed gas has high requirements for containers and harsh process requirements.

[0004] There are two main ways to store hydrogen chemically: one is to react hydrogen with metals to form metal hydrides to store hydrogen. The most typical example is MgH 2 、PdH、LaNi 5 The hydrides formed by this type of hydrogen storage method are highly stable and easy to transport and store. However, the hydrides formed often have a very high hydrogen storage temperature (about 300°C), harsh reaction conditions, and high requirements for the material dehydrogenation environment. The other type is to use naturally occurring hydride materials to react and release hydrogen, such as ammonia borane (NH 3 BH 3), hydrolysis of sodium borohydride (NaBH 4 ). However, this material can only release hydrogen once and cannot store hydrogen reversibly. It also has the disadvantages of high reaction temperature and the presence of by-products during the hydrogen release process, which makes these hydrogen storage materials difficult to put into use.

[0005] Physical adsorption hydrogen storage is a new type of hydrogen storage method developed in recent years. Currently, the most studied methods mainly include three categories: Metal Organic Frameworks (MOF) materials, MXene materials and carbon-based nanomaterials. This hydrogen storage method mainly utilizes the strong adsorption capacity of hydrogen storage materials for hydrogen, so that hydrogen and materials are connected by van der Waals bonds, thereby realizing the storage of hydrogen. Compared with the first two hydrogen storage methods, this hydrogen storage method has the advantages of high hydrogen storage, strong safety and low reaction conditions. Pure physical adsorption hydrogen storage materials often fail to meet the hydrogen storage requirements, so people enhance the hydrogen storage performance of materials by doping metal atoms with stronger adsorption capacity for hydrogen on the materials. However, due to the large cohesive energy of metal atoms, the doped metal atoms are easy to detach from the material and form clusters, which greatly reduces the hydrogen storage capacity of the material and also makes the existing physical adsorption hydrogen storage materials unable to be used for a long time. Therefore, finding a high-density physical adsorption hydrogen storage material that can stably dope metal atoms is the key to solving the current hydrogen storage problem. Summary of the invention

[0006] To solve the above problems, as another aspect of the present application, the present application also proposes a physical adsorption hydrogen storage material method, which is universal and representative. New organic synthetic materials with similar characteristics to the new two-dimensional materials mentioned in the present application can be considered as hydrogen storage materials, and the hydrogen storage performance can be considered and studied through the technical solutions mentioned in the present application.

[0007] A prediction method for a physical adsorption hydrogen storage material, wherein the physical adsorption hydrogen storage material comprises a two-dimensional nanomaterial doped with metal atoms, and the prediction method comprises the following steps:

[0008] 1) Setting the atomic coordinates and building the material structure according to the bond lengths and bond angles between the atoms of the reaction raw materials of the two-dimensional nanomaterial;

[0009] 2) inputting the material structure constructed in step 1) into a computer software for atomic-scale material simulation for computational optimization to obtain an optimized stable material structure;

[0010] 3) In the computer software for atomic-scale material simulation, the hydrogen atom groups at the armchair boundary positions of the stable material structure are replaced with metal atoms, and the binding energy and maximum hydrogen storage weight fraction of the titanium atoms in the material structure doped with metal atoms are calculated.

[0011] Optionally, in step 2), computer software for atomic-scale material simulation is used to self-consistently solve the Kohn-Sham equation through density functional theory to obtain the ground state energy of the system in multiple electrons; when the atomic real energy in the system reaches the convergence criterion, a stable material structure is obtained.

[0012] Optionally, the convergence criteria are: the cutoff energy is 400 eV, the force on each atom is less than

[0013] Optionally, the two-dimensional nanomaterial has a hollow structure, and the armchair boundary position is located within the hollow structure.

[0014] Optionally, the two-dimensional nanomaterial comprises the following structural unit I:

[0015]

[0016] Optionally, the method for calculating the binding energy and maximum hydrogen storage weight fraction of titanium atoms in the material structure doped with metal atoms in step 3) comprises the following steps:

[0017] (a) The hydrogen atom group at an armchair boundary position in the central void of the stable material structure is removed and replaced by metal atom doping. After optimizing the material structure, the binding energy of the metal atom is calculated;

[0018] (b) repeating step (a) until metal atoms are doped to replace hydrogen atoms at all armchair boundary positions; obtaining the binding energy of metal atoms with different doping amounts;

[0019] (c) The material obtained in step (b) adsorbs hydrogen, and increases the number of hydrogen molecules adsorbed on each metal atom one by one until the binding energy of the newly added hydrogen molecules no longer meets the reversible hydrogen storage requirements at room temperature, and calculates the average binding energy of each hydrogen molecule and the hydrogen storage weight fraction of the material.

[0020] Another aspect of the present invention is to provide a physical adsorption hydrogen storage material, thereby obtaining a new type of physical adsorption hydrogen storage material, in which the hydrogen storage weight fraction can reach up to 7.86wt%. At the same time, the material itself is composed of only light atoms such as carbon, hydrogen, oxygen, nitrogen and doped metals, which reduces the weight of the hydrogen storage material itself and provides a new option for hydrogen storage and transportation.

[0021] A physical adsorption hydrogen storage material; wherein the two-dimensional nanomaterial comprises the following structural unit I:

[0022]

[0023] The hole in the center of the structural unit I contains 6 armchair boundaries; metal atoms replace the hydrogen atom group at at least one of the armchair boundary positions.

[0024] Optionally, the metal atom includes at least one of a titanium atom, a scandium atom, a lithium atom, a calcium atom, a magnesium atom, a chromium atom, and an iron atom.

[0025] Optionally, the metal atom is a titanium atom.

[0026] Optionally, the metal atom replaces a group of 3-6 hydrogen atoms at the armchair edge positions.

[0027] The preparation method of the above-mentioned physical adsorption hydrogen storage material comprises the following steps:

[0028] 1) preparing a two-dimensional nanomaterial, wherein the two-dimensional nanomaterial comprises a structural unit I;

[0029] 2) Use metal atoms to replace the hydrogen atoms at the armchair boundaries of two-dimensional nanomaterials.

[0030] Optionally, the preparation method of the two-dimensional nanomaterial is: reflux and stir the solution containing triphenylamine and tribromide pyridine to react, evaporate the solvent after the reaction is completed, and purify the product by column chromatography to obtain a precursor; through an Ullmann coupling reaction, debrominate the precursor and then couple it, and deposit it on the preheated Au single crystal surface to obtain the two-dimensional nanomaterial.

[0031] Optionally, the reaction conditions of the Ullmann coupling reaction are: the pressure is 1 to 3×10 -10 mbar, and the temperature is 390-410℃.

[0032] As a specific implementation in this application:

[0033] Step 1: Calculate the material P to be used in the simulation 2 The TANG structure was constructed and optimized using the VASP commercial computing software package to obtain the lowest energy stable structure and read the total energy of the unit cell in the calculation results.

[0034] Step 2: Remove the two hydrogen atoms at an armchair boundary position in the central cavity of the material from the structure optimized in step 1, calculate the doping of metal titanium atoms, optimize the structure, and read and calculate the binding energy of the titanium atoms.

[0035] Step 3 Repeat the operation of step 2 and finally 2 All six positions in the hexagonal voids of the TANG material are doped with metallic titanium atoms to obtain the final composite hydrogen storage material.

[0036] Step 4 uses the material obtained in step 3 to adsorb hydrogen, gradually increasing the hydrogen molecules adsorbed on each titanium atom until the binding energy of the newly added hydrogen molecules no longer meets the reversible hydrogen storage requirements at room temperature (0.2-0.6 eV), and finally calculates the average binding energy of each hydrogen molecule and the final hydrogen storage weight fraction of the material.

[0037] Optionally, the hydrogen storage material can be subjected to molecular dynamics simulation to demonstrate the stability of the material at room temperature and the rate of storing and releasing hydrogen.

[0038] Optionally, the hydrogen storage material can read the CHGCAR file and calculate and analyze the local charge density to observe the electron distribution and flow direction inside the material to analyze the rationality of the composite material structure.

[0039] The hydrogen atom group in this application refers to two hydrogen atoms on the armchair boundary structure.

[0040] The present invention is achieved by using a new two-dimensional material P 2 The doping of titanium atoms and the storage capacity of hydrogen were studied on TANG, and a new physical adsorption hydrogen storage material was successfully obtained that can stably dope titanium atoms and has a hydrogen storage weight density greater than the final requirement of DOE. The material itself has a large surface area to absorb hydrogen, and the material also has a side length of The hexagonal hole is thicker than graphene. GDY They are all large, which is conducive to the penetration and adsorption of hydrogen, as well as the doping of metal elements, which facilitates the chemical modification of materials and ensures that there is a certain distance between the doped metal atoms to reduce interactions. At the same time, this new type of hydrogen storage material does not use heavy metal elements, which ensures the lightness and portability of the material. This enables the material to solve the problems faced by most hydrogen storage materials. It provides a new method to solve the problem of difficulty in storage and transportation of hydrogen during use, and also opens up a new path for the realization of hydrogen energy vehicles with solid material hydrogen storage. At the same time, this method and calculation process for considering the hydrogen storage capacity of new materials also provides new ideas for people to find other new physical adsorption hydrogen storage materials.

[0041] The beneficial effects of this application include:

[0042] 1 This application is based on the new two-dimensional material P 2 By doping metallic titanium atoms into TANG, a new type of physical adsorption hydrogen storage material was obtained. The hydrogen storage weight fraction can reach up to 7.86wt%. At the same time, the material itself is composed of only light atoms such as carbon, hydrogen, oxygen, nitrogen and titanium, which reduces the weight of the hydrogen storage material itself and provides a new option for hydrogen storage and transportation.

[0043] 2 In the titanium-doped hydrogen storage material studied in this application, the binding energy between titanium atoms and the substrate can reach 6.65 eV on average, which is much larger than the binding energy of titanium metal bulk in experiments (4.85 eV) and theory (5.40 eV). This ensures the stability of titanium metal doping, thereby greatly improving the stability of the composite material and ensuring the service life of the hydrogen storage material.

[0044] 3 This application doped titanium atoms into a new two-dimensional material and then adsorbed hydrogen. The average binding energy of each hydrogen molecule is about 0.33 eV. This binding energy is between 0.2 eV and 0.6 eV, which is a necessary condition to ensure the reversible storage of hydrogen at room temperature, and broadens the application prospects of hydrogen storage materials.

[0045] 4 The material in this application has structural advantages. The material itself has a large central cavity, which increases the flow rate of hydrogen in the material and effectively shortens the reaction time of material storage and release of hydrogen.

[0046] 5 The research method mentioned in this application is universal and representative. New organic synthetic materials with similar characteristics to the new two-dimensional materials mentioned in this application can be considered as hydrogen storage materials, and the hydrogen storage performance can be considered and studied through the technical solutions mentioned in this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The optimized new two-dimensional material P in this application 2 Schematic diagram of the unit cell structure of TANG. The numbers 1, 2, and 3 represent three high-symmetry sites: 1. Armchair boundary; 2. Zigzag boundary; 3. Nitrogen atom head. In the figure, N1 and N2 are nitrogen atoms, O1, O2, and O3 are oxygen atoms, and the black atoms among the unlabeled atoms are carbon atoms, and the gray atoms are hydrogen atoms; the unit cell size is

[0048] Figure 2 The metal atom doping P is calculated in the embodiment of the present application. 2 Flowchart of TANG hydrogen storage performance.

[0049] Figure 3 This is a comparison chart of the binding energies of the materials obtained in Examples 1-4 of the present application and different metal atoms doped at different high symmetry points, including the experimental and calculated cohesive energy of the metal bulk.

[0050] Figure 4 Comparison of the binding energy of different numbers of titanium atoms obtained in Example 1 of the present application with the cohesive energy of bulk titanium metal.

[0051] Figure 5 This is a comparison chart of the average binding energy of hydrogen of the sample obtained in Example 1 of the present application and the room temperature reversible hydrogen storage standard. DETAILED DESCRIPTION

[0052] The calculation method in the embodiment of the present application is as follows:

[0053] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0054] The calculation used VASP (Vienna Ab-initio Simulation Package), a commercial software compiled by the Hafner group at the University of Vienna that can perform high-performance calculations on systems with periodic boundaries. This software uses density functional theory based on first principles and adopts ultrasoft pseudopotential or projected augmented wave methods to calculate the total energy of the electronic structure using an energy minimization scheme.

[0055] The constructed and optimized material structure is directly observed using VESTA material structure visualization tool software.

[0056] The parameters used in the calculations are as follows: the cutoff energy taken in the calculations is 400 eV;

[0057] The material structure is then optimized until the force on each atom is less than This can ensure that the total energy of the optimized structure is low enough and the structure is more stable;

[0058] Select the k-point setting K-POINT in the calculation to be 4×4×1;

[0059] In order to exclude the influence of interlayer spacing on the hydrogen storage capacity of the material, we set the vacuum layer between the two-dimensional material layers to The calculation parameters include but are not limited to these.

[0060] Example 1

[0061] Two-dimensional nanomaterials 2 Preparation method of TANG:

[0062] 17.1 g of pyridine tribromide was added to a solution of triphenylamine (1.5 g, 3.6 mmol), and the mixture was refluxed and stirred for 6 hours. The solution was evaporated, and the crude material was dissolved in ethyl acetate, washed with brine, and dried in vacuo. Purification by column chromatography gave a pale yellow solid (2.1 g, 89%), which was purified to give the precursor. -10 mbar pressure and 400℃, through Ullmann coupling reaction, in a size of 100×100nm 2The precursor obtained in the step is subjected to a debromination reaction and then coupled, and deposited on the preheated Au (111) single crystal surface to obtain the two-dimensional nanomaterial P 2 TANG.

[0063] In this embodiment, the steps of structure construction, structure optimization, metal atom doping and hydrogen adsorption are used to construct the P doped with metal titanium atoms. 2 TANG hydrogen storage materials. Figure 2 As shown, the specific operations include:

[0064] (1) According to the above preparation method P 2 The TANG structure is used to initially construct the unit cell, and the coordinates of all atoms are input based on key data such as the bond length and bond angle between atoms to build the material structure.

[0065] (2) Name the material structure file constructed in the previous step POSCAR as one of the input files for VASP software calculations. The file includes information such as lattice size, atomic type, and coordinates.

[0066] Then set up the input files required by other VASPs: INCAR mainly inputs various parameters that control the calculation system. It annotates the system conditions of the calculation, selects the calculation method and calibrates the convergence criteria: the cutoff energy is 400eV, the force on each atom is less than The parameter selection is as described above; KPOINTS inputs the setting mode of Brillouin zone k-point sampling: 4×4×1; POTCAR inputs the pseudopotential used in the calculation: GGA pseudopotential. All calculations in this application use the generalized gradient approximation (ie, GGA pseudopotential).

[0067] (3) Submit the four input files obtained in the previous step to the server for calculation, and use the VASP software package to perform structural optimization calculations on the material system. The VASP software uses density functional theory to self-consistently solve the Kohn-Sham equation to obtain the ground state energy of the system in multiple electrons. When the atomic real energy in the system reaches the force and energy convergence accuracy we calibrated in INCAR, it can be considered that the system has reached a stable structure. At this time, the atoms in the system have been sufficiently relaxed, and the structure is reasonable enough under our calibrated conditions. The structure obtained after optimization is as follows Figure 1 shown.

[0068] (4) The material obtained in the previous step is doped with metal titanium atoms. We gradually remove the six groups of two hydrogen atoms at the six armchair positions of the central cavity of the material to enhance the material's adsorption capacity for doped metal atoms, and dope metal atoms at the vacant high symmetry points respectively. After that, the structure is optimized respectively, and the binding energy of doping 1-6 metal titanium atoms is calculated, as shown in FIG. Figure 4As shown, to observe the stability of titanium atom doping.

[0069] (5) We adsorb hydrogen molecules on the material doped with 6 titanium atoms, gradually increasing the number of adsorbed hydrogen molecules, e.g. Figure 5 As shown, the maximum hydrogen storage weight fraction of the material that can meet the above conditions is observed. 2 TANG's theoretical maximum hydrogen storage capacity.

[0070] Example 2

[0071] In this embodiment, the steps of structure construction, structure optimization, metal atom doping and hydrogen adsorption are used to construct the P doped with metal lithium atoms. 2 The calculation process of TANG hydrogen storage material is basically the same as that of Example 1. The difference is that metal lithium atoms are used for doping and the hydrogen storage capacity is calculated.

[0072] Example 3

[0073] In this embodiment, the steps of structure construction, structure optimization, metal atom doping and hydrogen adsorption are used to construct the P doped with metal calcium atoms. 2 The calculation process of TANG hydrogen storage material is basically the same as that of Example 1. The difference is that metal calcium atoms are used for doping and the hydrogen storage capacity is calculated.

[0074] Example 4

[0075] In this embodiment, the steps of structure construction, structure optimization, metal atom doping and hydrogen adsorption are used to construct the P doped with metal scandium atoms. 2 TANG hydrogen storage material, the calculation process is basically the same as that of Example 1. The difference is that metal scandium atoms are used for doping and the hydrogen storage capacity is calculated. The results obtained in the above four examples are analyzed.

[0076] First, P 2 The removal of two hydrogen atoms at the armchair position 3 of the TANG site and then doping with metal atoms can significantly increase the binding energy of metal atoms, such as Figure 3 The gain effect produced by this operation is common because the removal of hydrogen atoms leads to the generation of free charges on the carbon atoms in the armchair positions, which generate strong attraction between these charges and metal atoms, greatly increasing the binding energy of metal atoms. The enhanced binding energy is much larger than the cohesive energy of the metal bulk itself obtained in the calculation and experiment, which ensures the stability of metal atom doping.

[0077] Secondly, because titanium atoms have the largest binding energy and the strongest adsorption capacity for hydrogen molecules, other metal atoms are difficult to reach the hydrogen storage standards specified by DOE after calculation. Therefore, titanium is the most suitable material to be doped into P 2 Metal atoms on TANG.

[0078] Then, the doping of titanium metal atoms is gradually increased. Since there are 6 identical armchair sites in the primitive cell of the material, up to 6 titanium atoms can be stably doped in one primitive cell. The distance between these 6 titanium atoms is This spacing can also ensure that the titanium atoms are relatively independent and do not affect each other, and also ensure space for the material to store hydrogen.

[0079] Finally, the hydrogen storage performance of the composite material was calculated in a primitive cell doped with 6 titanium atoms. Because room temperature reversible hydrogen storage requires that the binding energy of hydrogen cannot be too high, which will make it difficult to release hydrogen; nor can it be too low, which will lead to unstable hydrogen storage. Therefore, the binding energy of hydrogen at 0.2eV-0.6eV is one of the necessary conditions for room temperature reversible hydrogen storage. According to this condition, we gradually increase the number of adsorbed hydrogen (since hydrogen storage between titanium atoms is relatively independent, we can regard the number of adsorbed hydrogen on each titanium atom as the same, which is convenient for calculation without affecting the final result). The average binding energy of each hydrogen is calculated as follows Figure 5 As shown, it remains within the calibration range throughout the entire process, indicating that the material can achieve reversible hydrogen storage at room temperature.

[0080] Example 5

[0081] In this embodiment, the final hydrogen storage structure obtained in Example 1 is subjected to a hydrogen release simulation to determine the reversibility of the hydrogen storage performance of the hydrogen storage material. By removing hydrogen from the final material that has adsorbed hydrogen in Example 1 and simulating the process of hydrogen release from the material, it can be finally obtained that the decrease in the binding energy of the material when each hydrogen on each titanium atom is released is almost the same as the increase in the binding energy of hydrogen. The average binding energy of each hydrogen in the simulated release process of hydrogen is also between 0.2-0.6 eV. According to the conditions of reversible hydrogen storage, hydrogen can be reversibly stored and released in the material.

[0082] Comparative Example 1

[0083] In this comparative example, the steps of structure construction, structure optimization, metal atom doping and hydrogen adsorption are used to construct the metal atom-doped P 2 TANG hydrogen storage material. The preliminary operation steps of this comparative example are the same as the first three steps of Example 1. And the optimized P 2 TANG structure.

[0084] Then calculate the optimized structure obtained in the previous step. Place the metal atom directly on top of the nitrogen atom, such as Figure 1 The site 1 in the structure is optimized and the binding energy of the metal atom is calculated. The calculation results are shown in Figure 3 The calculation site 1 is shown in FIG.

[0085] Comparative Example 2

[0086] This comparative example is basically the same as comparative example 1, except that the metal atoms doped in the test calculation are directly placed near the zigzag boundary in the material hole, such as Figure 1 The site 2 in the structure is optimized and the binding energy of the metal atom is calculated. The calculation results are shown in Figure 3 The calculation site 2 is shown in FIG.

[0087] The main purpose of the comparative example is to find out that the binding energy of metal atoms directly placed on the material will be relatively small. This is also one of the reasons why metal atoms are difficult to stably dope in previous adsorption-type hydrogen storage materials. In this application, by selecting suitable materials and removing hydrogen atoms on the materials before doping with metal atoms, the stability of metal atom doping is improved and this problem is solved.

[0088] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A prediction method for physical adsorption hydrogen storage materials, It is characterized in that The physical adsorption hydrogen storage material includes a two-dimensional nanomaterial doped with metal atoms, and the prediction method includes the following steps: 1) Setting the atomic coordinates and building the material structure according to the bond lengths and bond angles between the atoms of the reaction raw materials of the two-dimensional nanomaterial; 2) inputting the material structure constructed in step 1) into a computer software for atomic-scale material simulation for computational optimization to obtain an optimized stable material structure; 3) In computer software for atomic-scale material simulation, the hydrogen atom groups at the armchair boundary positions of the stable material structure are replaced with metal atoms, and the binding energy and maximum hydrogen storage weight fraction of the metal atoms in the metal atom-doped material structure are calculated; Wherein, the two-dimensional nanomaterial comprises the following structural unit I: The hole in the center of the structural unit I contains 6 armchair boundaries; the metal atom replaces the hydrogen atom group at at least one of the armchair boundary positions; The metal atoms include at least one of titanium atoms, scandium atoms, lithium atoms, calcium atoms, magnesium atoms, chromium atoms, and iron atoms.

2. The prediction method according to claim 1, It is characterized in that In the step 2), computer software for atomic-scale material simulation is used to self-consistently solve the Kohn-Sham equation through density functional theory to obtain the ground state energy of the system in multiple electrons; when the atomic real energy in the system reaches the convergence standard, a stable material structure is obtained.

3. The prediction method according to claim 2, It is characterized in that The convergence criteria are: the cutoff energy is 400 eV, the force on each atom is less than The two-dimensional nanomaterial has a hollow structure, and the armchair boundary position is located in the hollow structure.

4. The prediction method according to claim 1, It is characterized in that The method for calculating the binding energy and the maximum hydrogen storage weight fraction of the titanium atoms in the material structure doped with metal atoms in step 3) comprises the following steps: (a) The hydrogen atom group at an armchair boundary position in the central void of the stable material structure is removed and replaced by metal atom doping. After optimizing the material structure, the binding energy of the metal atom is calculated; (b) repeating step (a) until metal atoms are doped to replace hydrogen atoms at all armchair boundary positions; obtaining the binding energy of metal atoms with different doping amounts; (c) The material obtained in step (b) adsorbs hydrogen, and increases the number of hydrogen molecules adsorbed on each metal atom one by one until the binding energy of the newly added hydrogen molecules no longer meets the reversible hydrogen storage requirements at room temperature, and calculates the average binding energy of each hydrogen molecule and the hydrogen storage weight fraction of the material.

5. A physical adsorption hydrogen storage material, It is characterized in that The structure of the physical adsorption hydrogen storage material is predicted by the prediction method according to any one of claims 1-4.

6. The physical adsorption hydrogen storage material according to claim 5, It is characterized in that The metal atom replaces a group of 3 to 6 hydrogen atoms at the armchair edge positions.

7. A method for preparing a physical adsorption hydrogen storage material according to any one of claims 5 to 6, It is characterized in that The steps include: 1) preparing a two-dimensional nanomaterial, wherein the two-dimensional nanomaterial comprises a structural unit I; 2) Use metal atoms to replace the hydrogen atom groups at the armchair boundary positions within the hollow structure of two-dimensional nanomaterials.

8. The method for preparing the physical adsorption hydrogen storage material according to claim 7, It is characterized in that The preparation method of the two-dimensional nanomaterial comprises: refluxing and stirring a solution containing triphenylamine and tribromide pyridine for reaction, evaporating the solvent after the reaction is completed, and purifying the product by column chromatography to obtain a precursor; Through the Ullmann coupling reaction, the precursor is subjected to a debromination reaction and then coupled, and then deposited on the surface of a preheated Au single crystal to obtain the two-dimensional nanomaterial.

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