Method for improving thermoelectric performance of two-dimensional graphene-based topological material

Abstract

The invention discloses a method for improving thermoelectric performance of a two-dimensional graphene-like topological material, and belongs to the technical field of new energy materials. The electronic structure parameters of the hydrogenated modified material are calculated through the density functional theory, and then the hydrogen modified material with the proper structure is screened; analyzing the thermal stability at high temperature through AIMD molecular dynamics simulation; the Seebeck coefficient of the target hydrogenation model is calculated through the Boltzmann transport theory; the lattice thermal conductivity of a target hydrogenation model is calculated through ShengBTE software, the conductivity is calculated in combination with a BoltzTraP2 code, the thermoelectric figure of merit of the material is obtained, the material structure with excellent thermoelectric performance and high-temperature structural stability is obtained through calculation, and a reliable path is provided for improvement of the thermoelectric performance of the two-dimensional material. The method breaks through the limitation of a traditional doping or composite modification method, is not only suitable for graphene-like materials, but also can be popularized to other two-dimensional materials and novel semiconductor systems, and has high applicability and perspectiveness.

Description

Technical Field

[0001] The invention relates to a method for improving the thermoelectric performance of a two-dimensional graphene-based topological material, and belongs to the technical field of new energy materials. Background Art

[0002] With the continuous development of science and technology, thermoelectric materials, as a functional material that can directly realize the mutual conversion of thermal energy and electrical energy, are increasingly valued in the fields of energy utilization, refrigeration equipment and space exploration. These materials are usually required to have a high thermoelectric figure of merit (zT) to achieve more efficient energy conversion efficiency. However, most of the current thermoelectric materials, while improving their performance, are often accompanied by problems such as reduced material stability, increased production costs and limited scope of application.

[0003] In recent years, two-dimensional graphene-based materials have shown great potential in the field of thermoelectrics due to their unique physical and chemical properties and structural flexibility. Traditional methods for improving the performance of two-dimensional materials mainly rely on technologies such as doping, composite and surface functionalization. Although these methods have improved thermoelectric performance to a certain extent, they have limitations such as complex operation and limited performance improvement.

[0004] Although existing modification methods have made some progress in improving thermoelectric performance, the following problems still exist: (1) There is a lack of systematic optimization strategies in the material modification process, making it difficult to achieve a balance between performance improvement and material stability. (2) Some modification methods have strict requirements on material preparation conditions, which limits their promotion and application in actual production. (3) Performance improvement is mainly focused on electrical transport optimization, and thermal conductivity regulation technology is not yet mature, making it difficult to further improve the overall thermoelectric figure of merit.

[0005] In response to the above problems, the present invention proposes a method for improving the thermoelectric properties of two-dimensional graphene-based topological materials, providing a novel and feasible technical approach for the research and development of high-efficiency thermoelectric materials. Summary of the invention

[0006] In order to overcome the problems in the background technology, the purpose of the present invention is to provide a method for improving the thermoelectric properties of two-dimensional graphene-based topological materials, and to guide the improvement of the thermoelectric properties of two-dimensional graphene-based topological materials.

[0007] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0008] A method for improving the thermoelectric performance of a two-dimensional graphene-based topological material comprises the following steps:

[0009] (1) Construct hydrogenation models based on two-dimensional graphene-based materials with topological properties;

[0010] (2) optimizing the constructed hydrogenation model by first-principles calculation to obtain the electronic structure parameters of the hydrogenated material. When the electronic structure parameters meet the conditions, the hydrogenation model is the target hydrogenation model;

[0011] (3) Through AIMD molecular dynamics simulation, the thermal stability of the target hydrogenation model at high temperature is analyzed;

[0012] (4) Using the Boltzmann transport theory, calculate the Seebeck coefficient of the target hydrogenation model;

[0013] (5) The lattice thermal conductivity of the target hydrogenated model was calculated using ShengBTE software, and the electrical conductivity was calculated using the BoltzTraP2 code, ultimately yielding the thermoelectric figure of merit of the material.

[0014] When the thermoelectric figure of merit zTafter of the hydrogenated material is higher than that before hydrogenation, and the AIMD calculation shows that the hydrogenated material maintains chemical stability within the target operating temperature range (e.g., 300-800K) without phase change or decomposition (use VESTA software to view the CONTCAR file generated after the calculation to view the chemical bond breakage between atoms), it indicates that the material has good thermoelectric performance. If the thermoelectric figure of merit and thermal stability do not meet the above conditions, then the hydrogen atom adsorption position and adsorption quantity (i.e., hydrogenation ratio and distribution) in the hydrogenation model in step (1) are changed to re-establish a new hydrogenation model so that the new hydrogenation model meets the thermoelectric figure of merit and thermal stability conditions.

[0015] More preferably, the thermoelectric figure of merit of the hydrogenated material / the thermoelectric figure of merit of the material before hydrogenation is greater than 1.2, and using AIMD calculation, the hydrogenated material maintains chemical stability within the target operating temperature range (such as 300-800K) without phase change or decomposition, indicating that the material has excellent thermoelectric properties.

[0016] The present invention constructs a method for improving the thermoelectric properties of two-dimensional graphene-based topological materials through theoretical calculations to ensure that the material maintains high-temperature structural stability while improving the thermoelectric performance.

[0017] Preferably, the two-dimensional material with topological properties includes but is not limited to graphene, borophene, transition metal sulfide and other graphene-like materials. More preferably, the two-dimensional graphene-like material with topological properties is graphene, borophene or transition metal sulfide.

[0018] Preferably, the hydrogenation model is a model of hydrogen atom adsorption behavior at different positions on a two-dimensional graphene-based material with topological properties, and the adsorption behavior is single-sided hydrogenation, double-sided hydrogenation or partial hydrogenation.

[0019] Preferably, the hydrogenation model is subjected to density functional theory calculation using VASP software package, during which the electronic structure parameters of the hydrogenated material are obtained by hybrid functional calculation using PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof2006).

[0020] Preferably, the electronic structure parameters include electronic energy band, state density and effective mass.

[0021] Preferably, in step (2), when the energy convergence is less than 10 -6 eV, the force converges to less than , the optimization is completed.

[0022] Preferably, in step (2), when the electron energy band is 0.2-2.0 eV, the state density is within the range of ±0.1 eV of the Fermi level, and the local state density needs to reach 10^21 states / eV·cm 3 When the above conditions are met and more than two energy level degeneracy phenomena are shown in the energy level distribution, and the effective mass of electrons or holes is 0.15 to 1.5 times of the electron mass, the hydrogenation model is the target hydrogenation model; otherwise, the hydrogen atom adsorption behavior of the hydrogenated material is changed to recreate the hydrogenation model until the electronic structure parameters of the hydrogenation model meet the conditions, then the hydrogenation model is the target hydrogenation model.

[0023] Local Density of States (LDOS) is a description of the density of states at a specific location / energy range or local area, such as the distribution of electronic states around a certain atom or at a specific location in a crystal lattice.

[0024] The energy level degeneracy phenomenon is that the interval between multiple energy levels is less than 0.01eV.

[0025] Beneficial effects of the present invention: The present invention calculates the electronic structure parameters of hydrogenated modified materials by density functional theory, and then screens hydrogen-modified materials with suitable structures; then analyzes thermal stability at high temperatures by AIMD molecular dynamics simulation; calculates the Seebeck coefficient of the target hydrogenated model by Boltzmann transport theory; uses ShengBTE software to calculate the lattice thermal conductivity of the target hydrogenated model, and combines the BoltzTraP2 code to calculate the electrical conductivity to obtain the thermoelectric figure of merit of the material. The material structure with excellent thermoelectric performance and high-temperature structural stability is obtained by the above calculation, which provides a reliable path for improving the thermoelectric performance of two-dimensional materials. In addition, the method described in the present invention breaks through the limitations of traditional doping or composite modification methods, and is not only applicable to graphene-like materials, but can also be extended to other two-dimensional materials and new semiconductor systems, and has high applicability and foresight. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagrams of the structures of the unhydrogenated graphene and the target hydrogenated model 2H-graphenylene created in Example 1, (a) is a schematic diagram of the structure of the unhydrogenated graphene, and (b) is a schematic diagram of the structure of the target hydrogenated model 2H-graphenylene.

[0027] Figure 2 Energy band diagram of the target hydrogenation model 2H-graphenylene.

[0028] Figure 3 The electron localization function diagram of the target hydrogenation model 2H-graphenylene.

[0029] Figure 4 The Seebeck coefficient diagram of the target hydrogenated model 2H-graphenylene calculated in Example 1 at different temperatures, (a) is a functional relationship diagram between the Seebeck coefficient values ​​of n-type and p-type 2H graphene and the carrier concentration at 300, 550 and 800K along the X direction. (b) is a functional relationship diagram between the Seebeck coefficient values ​​of n-type and p-type 2H graphene and the carrier concentration at 300, 550 and 800K along the Y direction.

[0030] Figure 5 The power factor diagram of the target hydrogenated model 2H-graphenylene calculated in Example 1 at different temperatures, (a) is the PF value of the p-type doped material at 300K, 550K and 800K, and (b) is the PF value of the n-type doped material at 300K, 550K and 800K.

[0031] Figure 6 This is the structural stability image of the target hydrogenated model 2H-graphenylenede calculated in Example 1 at 800K.

[0032] Figure 7 The phonon spectrum of the target hydrogenated model 2H-graphenylenede calculated in Example 1. In the figure, C is the phonon frequency of the C atom, and H is the phonon frequency of the H atom.

[0033] Figure 8Thermoelectric figures of merit of unhydrogenated graphene and target hydrogenated model 2H-graphenylene created in Example 1, (a) is the functional relationship between the thermoelectric figure of merit (ZT) and carrier concentration of n and p-type 2H-graphenylenede in the X direction at 300K, 550K and 800K, (b) is the functional relationship between the thermoelectric figure of merit (ZT) and carrier concentration of n and p-type 2H-graphenylenede in the Y direction at 300K, 550K and 800K, (c) is the functional relationship between the thermoelectric figure of merit (ZT) and carrier concentration of n and p-type unhydrogenated graphenylenede in the X direction at 300K, 550K and 800K, (d) is the functional relationship between the thermoelectric figure of merit (ZT) and carrier concentration of n and p-type unhydrogenated graphenylenede in the Y direction at 300K, 550K and 800K.

[0034] Fig. 9 Flowchart of a method for improving the thermoelectric properties of two-dimensional graphene-based topological materials. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] All chemical reagents not specified in the examples and comparative examples of the present invention were commercially available analytically pure for experiments.

[0037] Example 1

[0038] A method for improving the thermoelectric performance of a two-dimensional graphene-based topological material comprises the following steps:

[0039] (1) Graphene was selected as the research object. This two-dimensional material has a unique pore structure and stable energy band distribution. Through high-throughput calculations and screening of material databases (such as Materials Project, AFLOW, etc.), graphene was confirmed to have good electronic structure characteristics and geometric stability. In order to further optimize its thermoelectric performance, graphene was hydrogenated. A two-dimensional graphene model was established through MS (Materials Studio), and then the hydrogenation model was constructed by conducting hydrogen atom adsorption behavior at different positions on the two-dimensional graphene with topological characteristics; the adsorption behavior was single-sided hydrogenation, double-sided hydrogenation or partial hydrogenation.

[0040] The adsorption behavior (single-sided hydrogenation, double-sided hydrogenation or partial hydrogenation) described in the present invention is not the behavior of a single adsorption position, but a collective behavior including multiple possible adsorption positions. For example: Single-sided hydrogenation: hydrogen atoms may be adsorbed at the center, edge or hole position of the six-membered ring on the surface of the two-dimensional material, forming a variety of adsorption models. Double-sided hydrogenation: The distribution of hydrogen atoms on both sides of the surface can be a symmetrical distribution (such as adsorption corresponding to the center of the six-membered ring) or an asymmetric distribution (such as random adsorption). Partial hydrogenation: Adsorption may be concentrated in local areas of the material, such as edges, defect positions or near holes.

[0041] To ensure the comprehensiveness of the research, for each adsorption behavior (single-sided, double-sided, partial), the present invention establishes multiple hydrogenation models at multiple adsorption positions and adsorption ratios. In order to improve the calculation efficiency, density functional theory calculations are used to evaluate and compare the multiple hydrogenation models, thermal stability and thermoelectric figure of merit.

[0042] In summary, each adsorption behavior contains multiple adsorption positions and different adsorption quantities. The specific positions and quantities are determined through theoretical calculations and simulation screening to ensure the comprehensiveness and scientificity of the model.

[0043] (2) The constructed hydrogenation model was optimized by density functional theory (DFT) calculation using VASP (Vienna Ab-initio Simulation Package). During the calculation process, PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof2006) hybrid functionals were used for structural optimization. When the optimization condition reached an energy convergence of less than 10 -6 eV, the force converges to less than When the electron energy band is 0.2-2.0eV and the state density is within the range of ±0.1eV of the Fermi level, the local state density needs to reach 10 21 states / eV·cm 3When the above is true, and more than two energy level degeneracy phenomena are shown in the energy level distribution, and the effective mass of electrons or holes is 0.15 to 1.5 times the mass of electrons, the hydrogenation model is the target hydrogenation model; otherwise, the hydrogen atom adsorption behavior of the hydrogenated material is changed to recreate the hydrogenation model until the electronic structure parameters of the hydrogenation model meet the conditions, then the hydrogenation model is the target hydrogenation model. According to the density functional theory (DFT) calculation results, the adsorption energy of hydrogen atoms when adsorbed at the six-membered ring position is the lowest, and the adsorption behavior is the most stable. Compared with other adsorption positions (such as edges or holes), the six-membered ring position can maintain the electronic structure symmetry of graphene to the greatest extent, while significantly improving the thermoelectric properties of the material. In this embodiment, in the target hydrogenation model, hydrogen atoms are selectively adsorbed at the six-membered ring position of graphene to form a 2H-graphenylene structure (such as Figure 1 As shown in Figure 1 As shown in Figure 2, the 2H-graphenylene structure includes the symmetrical distribution of hydrogen atoms in the six-membered ring. Through selective adsorption, hydrogen atoms form a specific arrangement on the six-membered ring, resulting in the opening of the electronic band gap of the material and the change of the state density, which provides a basis for the improvement of thermoelectric performance.

[0044] S2-1: In the density functional theory (DFT) calculations, the Vienna ab initio simulation package (VASP) was used: First, the electronic structure was calculated by using the Perdew-Burke-Ernzerhof (PBE) functional in the generalized gradient approximation (GGA) to deal with the exchange-correlation contribution, combined with the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional to more accurately describe the band gap structure of the material.

[0045] In the specific calculation, the plane wave cutoff energy was set to 420-550 eV, and the Brillouin zone was sampled through a 6×6×1 k-point grid to ensure the calculation accuracy of the electronic energy band. In addition, to avoid interlayer interaction, a vertical The optimization of the lattice structure is done by setting the convergence criteria of force and energy as and 10 -6 Under these settings, the generated electronic band data can be extracted and plotted by post-processing tools (such as VASPkit or P4Vasp) to show the energy distribution and electronic state characteristics.

[0046] S2-2: The calculation of the density of states (DOS) is based on static calculations, and relevant parameters (such as LORBIT = 11 for outputting state density information; ISMEAR = -5 and SIGMA = 0.05 for bandgap materials) are set to improve the calculation accuracy. During the calculation process, the state density data is generated using an appropriate k-point grid, and the total state density (TDOS) and partial state density (PDOS) graphics and data are generated through tools (such as VASPkit) to analyze the electronic state distribution characteristics of the material.

[0047] S2-3: The calculation of effective mass is achieved by analyzing the dispersion relationship of the electron energy band (Ek curve). This study extracted the energy extreme points near the Fermi level and determined the effective mass of electrons and holes by calculating their second-order derivatives. The fitting and analysis of effective mass can be done automatically using the VASPkit software, or it can be calculated manually by fitting the energy band data. To ensure the accuracy of the calculation, high-precision calculation parameters (such as PREC=Accurate) are used, and a high-density k-point grid is used to sample the energy distribution in detail.

[0048] according to Figure 2 It can be seen that compared with the target hydrogenated model and the unhydrogenated graphene model, the hydrogenation treatment significantly changes the electronic structure of the material, especially the opening of the band gap and the electron localization phenomenon. The hydrogenated 2H-graphenylene shows a wider band gap than the original graphenylene (such as Figure 2 ) and more obvious electron localization phenomena (such as Figure 3 ), which provides a theoretical basis for its excellent thermoelectric performance. In addition, 2H-graphenylene changes the energy band distribution of the material, especially making the conduction band and valence band overlap with similar energy bands, increasing the effective carrier concentration of electrons in the material, and providing a good electronic structure foundation for the improvement of thermoelectric performance.

[0049] (3) At 800K, the hydrogenated material was simulated by ab initio molecular dynamics (AIMD) for 5ps (time step of 1fs) using the canonical ensemble (NVT) condition controlled by the Nosé-Hoover thermostat. The simulation showed that the hydrogenated material could still maintain a stable structure (e.g. Figure 6 ) and exhibits excellent thermal stability.

[0050] Phonon dispersion analysis confirmed that hydrogenation treatment led to enhanced phonon scattering of the material, successfully reducing the lattice thermal conductivity. Figure 7As shown, the experimentally measured phonon scattering spectrum is highly consistent with the results of simulation calculations, indicating that the effect of hydrogenation modification on phonon propagation is consistent with the calculated results, which provides theoretical support for the low lattice thermal conductivity of the material.

[0051] (4) The BoltzTraP2 code was used to calculate the Seebeck coefficient of hydrogenated 2H-graphenylene based on the Boltzmann transport theory. By comparing the electron transport properties of pristine graphene and hydrogenated 2H-graphenylene, the results show that the Seebeck coefficient of the hydrogenated material is significantly improved at higher carrier concentrations (e.g. Figure 4 ), the Seebeck coefficients of hydrogenated 2H-graphenylene at 300K, 550K, and 800K are 478.7μV / K, 458.1μV / K, and 412.1μV / K, respectively, while the maximum Seebeck coefficients of pristine graphene at 300K, 550K, and 800K are 147.2μV / K, 112.3μV / K, and 89.3μV / K, respectively.

[0052] At the same time, the power factor of hydrogenated 2H-graphenylene was also calculated based on the Boltzmann transport theory using the BoltzTraP2 code, and the power factor of hydrogenated 2H-graphenylene was also enhanced (e.g. Figure 5 ). The changes in Seebeck coefficient and power factor are mainly attributed to the band gap change and electron localization phenomenon, which effectively promote the improvement of the thermoelectric performance of 2H-graphenylene.

[0053] (5) Using ShengBTE (Boltzmann Transport Equation) software, calculate the lattice thermal conductivity of the target hydrogenated model through the Boltzmann transport equation, including: using VASP and related tools to generate second-order force constants (FORCE_CONSTANTS) and third-order force constants data to describe phonon frequency and scattering mechanism. Configure the parameters required by ShengBTE (such as Brillouin zone mesh density, temperature range, etc.), run the software and obtain the lattice thermal conductivity tensor results.

[0054] Then, based on the material band structure data (such as vasprun.xml), a high-density K-point grid is used to ensure the calculation accuracy, extract the key information of the material's Fermi level and electronic state density, and generate an input file. Configure the calculation parameters (such as temperature and carrier concentration range), run BoltzTraP2 and output the conductivity, and finally obtain the thermoelectric figure of merit of the material as 1.66.

[0055] Since the thermoelectric figure of merit of hydrogenated 2H-graphenylene is 1.66, which is greater than that of unhydrogenated graphene, and the hydrogenated 2H-graphenylene can still maintain a stable structure at 800K, the hydrogenated 2H-graphenylene material constructed by the present invention not only has excellent thermal stability, but also has good thermoelectric performance.

[0056] Example 2

[0057] In order to verify whether the method of Example 1 can provide guidance for the synthesis of materials and to verify the accuracy of the method for improving the thermoelectric properties of two-dimensional graphene-based topological materials described in the present invention, the experiment of Example 2 was set up to prepare the material of the structure constructed in Example 1, and the influence of hydrogenation modification on the electronic structure and lattice of the material was confirmed by characterization methods such as X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The Seebeck coefficient, electrical conductivity and thermal conductivity were tested using a thermoelectric measurement system, and the thermoelectric figure of merit (ZT) was calculated and compared with the theoretical results of Example 1.

[0058] A method for improving the thermoelectric performance of a two-dimensional graphene-based topological material comprises the following steps:

[0059] (1) A single-layer graphene film was grown on a porous copper foil using chemical vapor deposition (CVD) and then transferred to a Si / SiO2 substrate. Next, the material was annealed at 200°C for 2 hours in an argon environment to remove surface impurities and obtain graphene.

[0060] (2) Place graphene in a mixed atmosphere of argon and hydrogen (hydrogen concentration is 0.5%-2%), control the temperature at 250°C, and treat the sample for 2 hours under the excitation of a low-power (30-50W) plasma generator to activate the hydrogen to decompose and generate diatomic hydrogen. The material sample is cooled to room temperature under the protection of inert gas nitrogen. During this process, the sample is transferred to a vacuum drying oven to ensure its stability in a low-humidity environment. Subsequently, the sample surface is cleaned with an isopropanol solution to remove residual impurities and gas source reaction products to ensure that the surface of the material is clean and pure, and hydrogenated 2H-graphenylene is obtained. In the hydrogenated 2H-graphenylene structure, the hydrogen atoms are selectively adsorbed at the six-membered ring position of graphenylene, which is the same as the 2H-graphenylene model structure constructed in Example 1.

[0061] During the experiment, Raman spectroscopy and infrared spectroscopy were used to characterize the material and verify its thermal stability. Specifically, after hydrogenation of 2H-graphenylene at high temperature (800K), its Raman spectrum showed that the shifts of the G and D peaks were 1580cm -1and 1350cm -1 , the peak intensity ratio ID / IG changed by less than 5%, from 0.12 to 0.35, reflecting that the hydrogenation process introduced more lattice defects, indicating that the material structure remained stable at high temperatures. XPS analysis showed that before hydrogenation modification, C=C bonds accounted for 80% of the total area of ​​the C1s peak, while CC bonds accounted for 20%; after hydrogenation modification, the proportion of CH bonds increased significantly to 35%, indicating that hydrogenation modification successfully introduced a new chemical state. In addition, infrared spectroscopy tests showed that the CH bond absorption peak remained at 2950cm -1 These data indicate that the thermal stability of the experimentally prepared material is consistent with the calculated results ( Figure 7 ) is consistent.

[0062] The test material was cut into rectangular samples with a size of 10 mm × 2 mm × 1 mm. The sample surface was polished using a polishing machine to ensure smoothness and remove the oxide layer. Then, anhydrous ethanol or isopropyl alcohol was used to remove surface impurities.

[0063] The thermoelectric performance test system described in this embodiment includes: Seebeck coefficient test module; conductivity test module and thermal conductivity test module; temperature control system (heater and cooler): precise temperature control range: 300-800K; temperature difference range: 40-60K. Data acquisition equipment: high-precision voltmeter (precision ±1μV / pm); thermocouple and temperature controller (precision ±0.1K / pm).

[0064] The Seebeck coefficient, electrical conductivity and thermal conductivity modules are calibrated using standard samples such as Bi2Te3 or NiCr alloys.

[0065] The test steps for Seebeck coefficient, electrical conductivity and thermal conductivity include:

[0066] 1). Seebeck coefficient test

[0067] 1. Sample fixation: Mount both ends of the sample on the copper thermode to ensure close contact. Place two thermocouples on the sample surface to measure the temperature difference (ΔT).

[0068] 2. Temperature difference application: one end is heated to the target temperature (such as 800K), and the other end is maintained at a slightly lower temperature (such as 750K), forming a temperature difference of 50K.

[0069] 3. Data acquisition: record the temperature difference ΔT across the thermocouple and the thermoelectric potential (ΔV) across the sample.

[0070] 4. Calculate the Seebeck coefficient: S = ΔV / ΔT (unit: V / K or mV / K)

[0071] 2). Conductivity test

[0072] 1. Sample connection: Use the four-probe method: fix two pairs of current probes and voltage probes on the sample surface, and the test point spacing is about 5mm.

[0073] 2. Power-on measurement: Pass a known current and record the current value I and voltage drop V. Calculate the resistance R = V / I.

[0074] 3. Calculate the conductivity: σ = LR·A, where: L = 10 mm is the sample length; A = 2 mm is the cross-sectional area.

[0075] 3). Thermal conductivity test

[0076] 1. Sample installation: Fix the sample in the steady-state method or laser flash method test module. Install a heat flow meter or thermocouple on the sample surface to ensure that the test points are evenly distributed.

[0077] 2. Temperature difference application: Apply a known heat flux density q at both ends of the sample and record the temperature difference ΔT.

[0078] 3. Data recording: record the heat flux density and temperature difference in the state.

[0079] 4. Calculate thermal conductivity: κ = q·L / (ΔT·A)

[0080] Comprehensive analysis and calculation

[0081] 1. Calculation of thermoelectric figure of merit: Calculate zT=S based on the above measured data 2 *σ*T / κ, T is the measurement environment temperature.

[0082] 2. Data verification: Repeat each set of measurements 3 times and calculate the average value.

[0083] Compare the results with those of standard samples to ensure the accuracy and consistency of the data.

[0084] In the thermoelectric performance test, the Seebeck coefficient, electrical conductivity and thermal conductivity of the material measured by the thermoelectric measurement system were 246.7mV / K, 1.9*10 6 S / m and 85.6W / mK, the calculated ZT value is 1.081. Figure 8 As shown in the figure, by calculating the thermoelectric figure of merit (ZT) and comparing it with the theoretical calculation results, the effect of hydrogenation modification on the thermoelectric performance of the material is verified. A higher ZT value indicates that the material has higher efficiency in the thermoelectric conversion process, which is also a key indicator for evaluating thermoelectric performance. According to the experiment and the calculated ZT value after hydrogenation, it is 1.66 (the calculated ZT value is shown in Figure 8 (a), (b)), which is significantly higher than the original graphenylene without hydrogenation treatment, whose ZT value is about 0.47 (the calculated zT value is shown in Figure 8 (c), (d)). This result verifies that hydrogenation modification can effectively improve the thermoelectric performance of the material.

[0085] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials, characterized in that: The following steps are involved: (1) Construct hydrogenation models based on two-dimensional graphene-based materials with topological properties; (2) optimizing the constructed hydrogenation model by first-principles calculation to obtain the electronic structure parameters of the hydrogenated material. When the electronic structure parameters meet the conditions, the hydrogenation model is the target hydrogenation model; (3) Through AIMD molecular dynamics simulation, the thermal stability of the target hydrogenation model at high temperature is analyzed; (4) Using the Boltzmann transport theory, calculate the Seebeck coefficient of the target hydrogenation model; (5) The lattice thermal conductivity of the target hydrogenated model was calculated using ShengBTE software, and the electrical conductivity was calculated using the BoltzTraP2 code, ultimately yielding the thermoelectric figure of merit of the material.

2. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 1, characterized in that: The two-dimensional graphene-based material with topological properties is graphene, borophene or transition metal sulfide.

3. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 1, characterized in that: The hydrogenation model is a model of hydrogen atom adsorption behavior at different positions on a two-dimensional graphene-based material with topological properties, and the adsorption behavior is single-sided hydrogenation, double-sided hydrogenation or partial hydrogenation.

4. The method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 1, characterized in that: The density functional theory calculation of the hydrogenated model is performed by using the VASP software package, and in this process, the electronic structure parameters of the hydrogenated material are obtained by using PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof2006) hybrid functional calculations.

5. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 4, characterized in that: The electronic structure parameters include electronic energy band, state density and effective mass.

6. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 1, characterized in that: In step (2), when the energy convergence is less than 10 -6 eV, the force converges to less than , the optimization is completed.

7. A method for improving the thermoelectric performance of two-dimensional graphene-based topological materials according to claim 5, characterized in that: In step (2), when the electron energy band is 0.2-2.0 eV, the state density is within ±0.1 eV around the Fermi level, and the local state density must reach 10^21 states / eV·cm 3 When the above conditions are met and more than two energy level degeneracy phenomena are shown in the energy level distribution, and the effective mass of electrons or holes is 0.15 to 1.5 times of the electron mass, the hydrogenation model is the target hydrogenation model; otherwise, the hydrogen atom adsorption behavior of the hydrogenated material is changed to recreate the hydrogenation model until the electronic structure parameters of the hydrogenation model meet the conditions, then the hydrogenation model is the target hydrogenation model.

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