A method for improving thermoelectric performance of two-dimensional graphenelike topological material

Abstract

The application discloses a method for improving thermoelectric performance of two-dimensional graphenelike topological material, and belongs to the technical field of new energy materials. The electronic structure parameters of hydrogen-modified material are calculated through the density functional theory, and then the hydrogen-modified material with a suitable structure is screened; then the thermal stability under high temperature is analyzed through AIMD molecular dynamics simulation; the Seebeck coefficient of the target hydrogenated model is calculated through the Boltzmann transport theory; the lattice thermal conductivity of the target hydrogenated model is calculated by using ShengBTE software, the conductivity is calculated by combining BoltzTraP2 code, and the thermoelectric merit value of the material is obtained; the material structure with excellent thermoelectric performance and high-temperature structural stability is obtained through the above calculation, and a reliable path for improving the thermoelectric performance of two-dimensional material is provided. Moreover, the method breaks through the limitations of traditional doping or composite modification methods, is suitable for graphenelike materials, can be popularized to other two-dimensional materials and new semiconductor systems, and has high applicability and foresight.

Description

TECHNICAL FIELD

[0001] The application relates to a method for improving the thermoelectric performance of a two-dimensional graphene-like topological material and belongs to the technical field of new energy materials. BACKGROUND

[0002] With the continuous development of science and technology, thermoelectric materials, as a kind of functional material capable of directly realizing the mutual conversion between heat and electricity, are increasingly valued in the fields of energy utilization, refrigeration equipment and space exploration. These materials are usually required to have high thermoelectric figure of merit (zT) to achieve higher energy conversion efficiency. However, at present, most thermoelectric materials, while improving performance, often have problems such as reduced material stability, increased production cost and limited application range.

[0003] In recent years, two-dimensional graphene-like materials have shown great potential in the field of thermoelectricity due to their unique physical and chemical properties and structural flexibility. Traditional methods for improving the performance of two-dimensional materials mainly rely on doping, compounding and surface functionalization, etc. Although these methods have improved the thermoelectric performance to some 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, there are still the following problems: (1) There is a lack of systematic optimization strategy in the material modification process, making it difficult to balance performance improvement and material stability. (2) Some modification methods have strict requirements for material preparation conditions, limiting their application in actual production. (3) Performance improvement mainly focuses on optimizing electrical transport, and heat conductivity regulation technology is not mature, making it difficult to further improve the overall thermoelectric figure of merit.

[0005] In view of the above problems, the application provides a method for improving the thermoelectric performance of a two-dimensional graphene-like topological material, which provides a novel and feasible technical approach for the research and development of high-efficiency thermoelectric materials. SUMMARY

[0006] In order to overcome the problems in the background art, the purpose of the present application is to provide a method for improving the thermoelectric performance of a two-dimensional graphene-like topological material, and to guide the improvement of the thermoelectric performance of a two-dimensional graphene-like topological material.

[0007] In order to achieve the above-mentioned purpose, the present application realizes the following technical scheme:

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

[0009] (1) constructing a hydrogenation model based on a two-dimensional graphene-like material with topological properties;

[0010] (2) optimizing the hydrogenation model by first principle calculation to obtain the electronic structure parameters of the hydrogenated material, and the hydrogenation model is the target hydrogenation model when the electronic structure parameters meet the conditions;

[0011] (3) analyzing the thermal stability of the target hydrogenation model at high temperature by AIMD molecular dynamics simulation;

[0012] (4) calculating the Seebeck coefficient of the target hydrogenation model by using Boltzmann transport theory;

[0013] (5) calculating the lattice thermal conductivity of the target hydrogenation model by using ShengBTE software, and calculating the electrical conductivity by combining BoltzTraP2 code, and finally obtaining the thermoelectric figure of merit of the material.

[0014] When the thermoelectric figure of merit zTafter of the hydrogenated material is higher than the thermoelectric figure of merit before hydrogenation, and the hydrogenated material maintains chemical stability without phase change or decomposition phenomenon in the target working temperature (such as 300-800K) range by using AIMD calculation (using VESTA software to view the CONTCAR file generated after calculation to view the chemical bond rupture between atoms), it is indicated that the material has good thermoelectric performance, if the thermoelectric figure of merit and the thermal stability do not meet the above conditions, then the hydrogenation model in step (1) is changed to change the hydrogen atom adsorption position and the adsorption amount (i.e. hydrogenation ratio and distribution) to establish a new hydrogenation model so that the new hydrogenation model meets the conditions of thermoelectric figure of merit and thermal stability.

[0015] More preferably, the thermoelectric figure of merit of the hydrogenated material / the thermoelectric figure of merit of the material before hydrogenation>1.2, and the hydrogenated material maintains chemical stability without phase change or decomposition phenomenon in the target working temperature (such as 300-800K) range by using AIMD calculation, which indicates that the material has excellent thermoelectric performance.

[0016] The application constructs a method for improving the thermoelectric performance of two-dimensional graphene-like topological materials by theoretical calculation to ensure that the material maintains high-temperature structural stability while improving the thermoelectric performance.

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

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

[0019] Preferably, the electronic structure parameters of the hydrogenated material are calculated by using the VASP software package to perform density functional theory calculation on the hydrogenated model, in which PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof 2006) hybrid functionals are adopted.

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

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

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

[0023] The local density of states (LDOS) is a description of the state density of a specific position / some energy range or local region, for example, the electronic state distribution around a certain atom or a certain specific position of a crystal lattice.

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

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

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

[0027] Figure 2 The band diagram of the target hydrogenated model 2H-graphenylene.

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

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

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

[0031] Figure 6 The structure stability image of the target hydrogenated model 2H-graphenylene de calculated for Example 1 at 800 K.

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

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

[0034] Figure 9 A flow chart of a method for improving the thermoelectric performance of a two-dimensional graphitelike topological material. DETAILED DESCRIPTION

[0035] The application will be further described in connection with specific embodiments, but the scope of protection of the application is not limited thereto.

[0036] Chemical reagents not described in the examples and comparative examples of the application are commercially available and used in experiments in analytical purity.

[0037] Example 1

[0038] A method for improving the thermoelectric performance of a two-dimensional graphitelike topological material, comprising the following steps:

[0039] (1) Select graphene as the research object, this two-dimensional material has a unique pore structure and stable energy band distribution. Through high-throughput calculation and material database (such as Materials Project, AFLOW, etc.) screening, graphene is confirmed to have good electronic structure characteristics and geometric stability. In order to further optimize its thermoelectric performance, graphene is modified by hydrogenation. A two-dimensional graphene model is established by MS (Materials Studio), and then hydrogen atom adsorption behavior is performed on different positions of the two-dimensional graphene with topological characteristics to construct a hydrogenated model; the adsorption behavior is 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 application is not a single adsorption site behavior, but a collective behavior including multiple possible adsorption sites. For example: single-sided hydrogenation: hydrogen atoms can be adsorbed at the center of the six-membered ring on the surface of the two-dimensional material, at the edge position or at the hole position, forming multiple adsorption models. Double-sided hydrogenation: the distribution of hydrogen atoms on both sides of the surface can be symmetric distribution (such as six-membered ring center corresponding adsorption) or asymmetric distribution (such as random adsorption). Partial hydrogenation: adsorption can be concentrated in local areas of the material, such as edges, defect positions or near holes.

[0041] To ensure the comprehensiveness of the study, for each adsorption behavior (single-sided, double-sided, partial), the present application establishes multiple hydrogenation models at multiple adsorption sites and adsorption ratios. In order to improve computational efficiency, multiple hydrogenation models are evaluated by density functional theory calculations, and the thermal stability and thermoelectric optimization values are compared.

[0042] In summary, each adsorption behavior includes multiple adsorption sites and different adsorption quantities, and the specific position and quantity are determined by theoretical calculation and simulation screening, thereby ensuring the comprehensiveness and scientificity of the model.

[0043] (2) The constructed hydrogenation model is subjected to density functional theory (DFT) calculation using the VASP (Vienna Ab-initio Simulation Package) software package to optimize the hydrogenation model. In the calculation process, PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof 2006) hybrid functionals are used for structure optimization. When the optimization conditions reach energy convergence less than 10 -6 eV, force convergence less than , optimization is completed, and detailed analysis of electronic band, state density and effective mass is performed. When the electronic band is 0.2-2.0 eV, the state density is within the Fermi energy level ± 0.1 eV, and the local state density needs to reach 10 21 states / eV·cm 3The above, and in the energy level distribution shows more than two energy level degeneration phenomenon, the effective mass of electron or hole is 0.15-1.5 times the electron mass, the hydrogenation model is the target hydrogenation model; otherwise, change the hydrogen atom adsorption behavior of the hydrogenation material 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 calculation results of density functional theory (DFT), the adsorption energy of hydrogen atom 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 edge or hole), the six-membered ring position can maximize the symmetry of the electronic structure of graphene, while significantly improving the thermoelectric performance of the material. In this embodiment, the hydrogen atoms in the target hydrogenation model are selectively adsorbed at the six-membered ring position of graphene to form a 2H-graphenylene structure (as shown in Figure 1 The 2H-graphenylene structure includes the symmetric distribution of hydrogen atoms at the six-membered ring position, as shown in Figure 1 By selective adsorption, hydrogen atoms form a specific arrangement on the six-membered ring, resulting in the opening of the material's electronic band gap 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) calculation, the Vienna ab initio simulation package (VASP) was used: first, the calculation of the electronic structure was processed by using the Perdew-Burke-Ernzerhof (PBE) function in the generalized gradient approximation (GGA) to deal with the exchange correlation contribution, and 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 420-550eV, and the k-point grid of 6x6x1 was used to sample the Brillouin zone to ensure the calculation accuracy of the electronic band. In addition, to avoid the interaction between the layers, a vacuum layer of 20A was introduced in the vertical direction. The optimization of the lattice structure was completed by setting the convergence criteria of force and energy to and 10 -6 eV respectively. 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 calculation, and relevant parameters are set (such as LORBIT = 11 for outputting state density information; ISMEAR = -5 and SIGMA = 0.05 for band gap materials) to improve the calculation accuracy. In the calculation process, the state density data is generated by using appropriate k-point grid, and the total density of states (TDOS) and partial density of states (PDOS) are generated by using tools (such as VASPkit) to generate graphics and data for analyzing the electronic state distribution characteristics of the material.

[0047] S2-3: The calculation of effective mass is realized by analyzing the dispersion relation of electronic energy band (E-k curve). In this study, the energy extreme point near the Fermi level is extracted, and the effective mass of electron and hole is determined by calculating its second derivative. The fitting and analysis of effective mass can be automatically completed by using VASPkit software, or manually calculated by fitting band data. In order to ensure the accuracy of calculation, high-precision calculation parameters (such as PREC = Accurate) are used, and 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 hydrogenation model and the graphene model without hydrogenation, hydrogenation significantly changes the electronic structure of the material, especially the opening of the band gap and the phenomenon of electron localization. The hydrogenated 2H-graphenylene exhibits a wider band gap (such as Figure 2 ) and a more obvious electron localization phenomenon (such as Figure 3 ) than the original graphenylene, which provides a theoretical basis for its excellent thermoelectric performance. In addition, 2H-graphenylene changes the energy band distribution of the material, especially the overlap of the conduction band and the valence band with the similar energy band, which improves the effective carrier concentration of electrons in the material and provides a good electronic structure foundation for the improvement of thermoelectric performance.

[0049] (3) Under the condition of NVT (Nosé-Hoover thermostat control), the ab initio molecular dynamics (AIMD) simulation of the hydrogenated material was carried out for 5 ps (time step of 1 fs) at 800 K. The simulation shows that the hydrogenated material can still maintain a stable structure (such as Figure 6 ) at 800 K and exhibits excellent thermal stability.

[0050] Through phonon dispersion analysis, it is verified that the hydrogenation treatment leads to the enhancement of phonon scattering of the material, which successfully reduces the lattice thermal conductivity. Figure 7As shown, the experimentally measured phonon scattering spectrum is highly consistent with the results of simulation calculation, indicating that the effect of hydrogenation modification on phonon propagation is consistent with the calculation results, which provides theoretical support for the low lattice thermal conductivity of the material.

[0051] (4) The BoltzTraP2 code is used to calculate the Seebeck coefficient of 2H-graphenylene after hydrogenation based on the Boltzmann transport theory. By comparing the electronic transport properties of the original graphene and 2H-graphenylene after hydrogenation, the results show that the Seebeck coefficient of the modified material is significantly improved at high carrier concentration (such as Figure 4 ), the Seebeck coefficient of 2H-graphenylene after hydrogenation at 300K, 550K, 800K is 478.7μV / K, 458.1μV / K, 412.1μV / K, respectively, and the maximum Seebeck coefficient of the original graphene at 300K, 550K, 800K is 147.2μV / K, 112.3μV / K, 89.3μV / K, respectively.

[0052] At the same time, the BoltzTraP2 code is used to calculate the power factor of 2H-graphenylene after hydrogenation based on the Boltzmann transport theory, and the power factor of 2H-graphenylene after hydrogenation is also enhanced (such as Figure 5 ). The changes in Seebeck coefficient and power factor are mainly due to the changes in band gap and electron localization phenomenon, which effectively promote the improvement of thermoelectric performance of 2H-graphenylene.

[0053] (5) The ShengBTE (Boltzmann Transport Equation) software is used to calculate the lattice thermal conductivity of the target hydrogenation model through the Boltzmann transport equation, which includes: using VASP and related tools to generate second-order force constants (FORCE_CONSTANTS) and third-order force constant data to describe phonon frequency and scattering mechanism. Configure the required parameters of ShengBTE (such as Brillion zone grid density, temperature range, etc.), run the software and get the lattice thermal conductivity tensor results.

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

[0055] Since the thermoelectric figure of merit of the 2H-graphenylene after hydrogenation is 1.66, which is greater than that of graphene without hydrogenation, and the 2H-graphenylene after hydrogenation can still maintain a stable structure at 800K, the 2H-graphenylene material constructed by the present application 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 verify the accuracy of the method for improving the thermoelectric performance of two-dimensional graphite-like graphene-based topological materials, the experiment of example 2 is set, the material of the structure constructed in example 1 is prepared, the influence of hydrogenation modification on the electronic structure and lattice of the material is confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and other characterization means, the Seebeck coefficient, electrical conductivity and thermal conductivity are tested by using the thermoelectric measurement system, and the thermoelectric figure of merit (ZT) is calculated and compared with the theoretical result of example 1.

[0058] A method for improving the thermoelectric performance of two-dimensional graphite-like graphene-based topological materials, comprising the following steps:

[0059] (1) Using chemical vapor deposition (CVD) method to grow single-layer graphene film on porous copper foil, and then transferring it to Si / SiO2 substrate. Next, the material is annealed at 200℃ for 2 hours in an argon environment to remove surface impurities to obtain graphene.

[0060] (2) Put the graphene into an argon and hydrogen mixed atmosphere (hydrogen concentration is 0.5%-2%), control the temperature at 250℃, and treat the sample under the excitation of a low-power (30-50W) plasma generator for 2 hours, activate hydrogen gas to generate diatomic hydrogen, and cool the material sample to room temperature under the protection of inert gas nitrogen. During this process, the sample is transferred to a vacuum drying box to ensure its stability in a low humidity environment. Subsequently, the sample surface is cleaned with isopropyl alcohol solution to remove residual impurities and gas source reaction products, so as to ensure the surface cleanliness and purity of the material, and obtain 2H-graphenylene after hydrogenation. The hydrogen atoms in the structure of 2H-graphenylene after hydrogenation are selectively adsorbed at the six-membered ring position of graphenylene, which is the same as the model structure of 2H-graphenylene constructed in example 1.

[0061] During the experiment, Raman spectroscopy and infrared spectroscopy were used to characterize the material and verify the thermal stability of the material. Specifically, after the 2H-graphenylene after hydrogenation is treated at high temperature (800K), its Raman spectrum shows that the displacement of G peak and D peak is 1580cm -1and 1350 cm -1 The peak intensity ratio ID / IG changed 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 C1s peak area, and C-C bonds accounted for 20%; after hydrogenation modification, the proportion of C-H bonds increased significantly to 35%, indicating that the hydrogenation modification successfully introduced new chemical states. In addition, infrared spectroscopy tests showed that the C-H bond absorption peak position remained near 2950 cm -1 , consistent with the display on the phonon spectrum. These data show that the thermal stability of the material prepared in the experiment is consistent with the calculation results( Figure 7 ).

[0062] The test material is cut into a rectangular sample with dimensions of 10 mm x 2 mm x 1 mm. The surface of the sample is polished using a polishing machine to ensure smoothness and remove the oxide layer. Then use anhydrous ethanol or isopropanol to remove surface impurities.

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

[0064] Use standard samples (such as Bi2Te3 or NiCr alloy) to calibrate the Seebeck coefficient, electrical conductivity and thermal conductivity modules.

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

[0066] 1). Seebeck coefficient test

[0067] 1. Sample fixation: Install the sample at both ends on the copper thermoelectric electrode to ensure close contact. Place two thermocouples on the surface of the sample 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 between the two thermocouples and the thermoelectric potential (ΔV) between the two ends of the sample.

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

[0071] 2). Electrical conductivity test

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

[0073] 2. Current measurement: Apply a known current, record the current value I and voltage drop V. Calculate the resistance R = V / I.

[0074] 3. Calculate 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 uniform distribution of test points.

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

[0078] 3. Data recording: Record the heat flux and temperature difference at the steady state.

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

[0080] Comprehensive analysis and calculation

[0081] 1. Calculate the thermoelectric figure of merit: Calculate zT = S 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 with standard sample results to ensure data accuracy and consistency.

[0084] In the thermoelectric performance test, the thermoelectric measurement system was used to measure the Seebeck coefficient, electrical conductivity and thermal conductivity of the material, which were 246.7 mV / K, 1.9*10 6 S / m and 85.6 W / mK, and the calculated ZT value was 1.081. As Figure 8 shown, by calculating the thermoelectric figure of merit (ZT) and comparing it with the theoretical calculation results, the improvement effect of hydrogenation on the thermoelectric performance of the material was verified. 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 calculation, the highest ZT value after hydrogenation 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, with a ZT value of about 0.47 (the calculated zT value is shown inFigure 8 (c), (d)). This result verifies that the hydrogenation modification can effectively improve the thermoelectric performance of the material.

[0085] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various modifications can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A method for improving the thermoelectric properties of two-dimensional graphene-based topological materials, characterized in that: Includes the following steps: (1) A hydrogenation model is constructed based on a two-dimensional graphene-like material with topological properties; the hydrogenation model is a model of hydrogen atom adsorption behavior at different positions on a two-dimensional graphene-like material with topological properties, wherein the adsorption behavior is single-sided hydrogenation, double-sided hydrogenation or partial hydrogenation. (2) Optimize the constructed hydrogenation model using first-principles calculations to obtain the electronic structure parameters of the hydrogenation material. When the electronic band is 0.2~2.0 eV, the density of states is within ±0.1 eV near the Fermi level, the local density of states must reach more than 10^21 states / eV·cm³, and more than two energy level degeneracy phenomena are shown in the energy level distribution. When the effective mass of electrons or holes is 0.15~1.5 times the electron mass, the hydrogenation model is the target hydrogenation model. Otherwise, change the hydrogen atom adsorption behavior of the hydrogenation material and 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. (3) The thermal stability of the target hydrogenation model at high temperature was analyzed by AIMD molecular dynamics simulation; (4) Using Boltzmann transport theory, calculate the Seebeck coefficient of the target hydrogenation model; (5) The thermal conductivity of the target hydrogenation model was calculated using ShengBTE software, and the electrical conductivity was calculated using BoltzTraP2 code. Finally, the thermoelectric figure of merit of the material was obtained.

2. The method for improving the thermoelectric properties 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, boronene, or a transition metal sulfide.

3. A method for improving the thermoelectric properties of two-dimensional graphene-based topological materials according to claim 1, characterized in that: The density functional theory calculations of the hydrogenation model were performed using the VASP software package. During this process, the electronic structure parameters of the hydrogenation material were obtained by hybrid functional calculations using PBE (Perdew-Burke-Ernzerhof) and HSE06 (Heyd-Scuseria-Ernzerhof 2006).

4. The method for improving the thermoelectric properties of two-dimensional graphene-based topological materials according to claim 3, characterized in that: The electronic structure parameters include electronic band structure, density of states, and effective mass.

5. The method for improving the thermoelectric properties 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, force convergence less than 10 -3 Optimization is complete at eV / Å.

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