A two-dimensional flexible composite material and a method for preparing the same

Abstract

This application provides a two-dimensional flexible composite material and its preparation method. The method involves heat-treating Bi₂Te₃ nanosheets to increase crystallinity and enhance the electrical conductivity of the two-dimensional ternary composite material. The Bi₂Te₃ / rGO mixture is then placed in a DMSO-treated PEDOT:PSS solution, which generates an interfacial scattering effect, reducing the thermal conductivity of the composite material and improving its thermoelectric conversion efficiency. Furthermore, PEDOT serves as a flexible matrix, while Bi₂Te₃ is a rigid material, enabling the formation of an interfacial layer with a large specific surface area and strong adhesion in the rGO binary composite material. This not only improves the mechanical stability of the composite film but also allows the material to withstand repeated bending without compromising its thermoelectric properties. The preparation steps employed in this method are simple and easily scalable. The addition of sodium dodecyl sulfonate enhances the surface activity of the Bi₂Te₃ nanosheets, achieving surface modification and improving the interfacial compatibility between rGO, Bi₂Te₃, and PEDOT, thereby enhancing the overall performance and long-term stability of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, specifically relating to a two-dimensional flexible composite material and its preparation method. Background Technology

[0002] Flexible thermoelectric materials, as key carriers for next-generation energy conversion technologies, have shown great potential in electronic sensing, microelectronic system functions, and solid-state refrigeration. Among them, Bi2Te3 is considered an ideal candidate material due to its excellent room-temperature thermoelectric properties, but its intrinsic brittleness makes it prone to fracture when bent to a diameter exceeding 8 mm, which severely restricts its flexible applications.

[0003] Existing technologies mainly achieve flexibility through polymer composites. For example, while PEDOT:PSS has good ductility, its inherent low conductivity limits thermoelectric conversion efficiency, requiring the addition of polar solvents such as acids and alkalis for adjustment. Furthermore, Bi₂Te₃ has a high Seebeck coefficient but low conductivity, and PEDOT exfoliated with polar solvents has high conductivity but a low Seebeck coefficient, indicating challenges in binary material composites. Patent CN113896838 uses Bi₂Te₃ nanosheets combined with PEDOT, reducing the bending radius to 5 mm, but exhibits a significant interfacial energy filtering effect, resulting in a conductivity of only 185 S / cm. Wang et al. used nanolithography to prepare PEDOT / Bi₂Te₃ composite films. A nanopore array template was prepared on a SiO₂ / Si substrate via nanolithography and hydrofluoric acid etching. Bi₂Te₃ was deposited into the template using thermal evaporation, followed by template removal. Then, a 70 nm diameter Bi2Te3 nanosphere array is generated in the PEDOT channel using a gas-phase polymerization process. Phonons are scattered by the Bi2Te3 nanolayer, and electron transport is retained in the continuous PEDOT, thereby improving the thermoelectric conversion performance of the composite film. However, this method is complex and requires high-end equipment, making it unsuitable for large-scale industrial production of flexible thermoelectric films.

[0004] Graphene, a carbon-based material, possesses excellent electrical conductivity. Introducing graphene to optimize the interface between graphene and carbon-based materials facilitates carrier transport; however, this method has not been reported in the material research of two-dimensional ternary composite films. Reduced graphene has attracted widespread attention from electrical materials researchers due to its high carrier mobility, but challenges remain in its composition design. While adding reduced graphene increases conductivity, excessive amounts can cause a surge in carrier concentration, leading to a decrease in the Seebeck coefficient. Furthermore, the formation of stacked reduced graphene layers can hinder carrier transport.

[0005] Therefore, the optimization of the composition and structural design of ternary composite materials are key issues that urgently need to be addressed in the research and application of flexible thermoelectric materials. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this application provides a two-dimensional flexible composite material and its preparation method. By precisely controlling the amount of reduced graphene, the conductivity, Seebeck coefficient, and mechanical flexibility of the composite material are balanced, thereby realizing the preparation of high-performance flexible thermoelectric materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In the first aspect, the present invention provides a method for preparing a two-dimensional flexible composite material, comprising the following steps:

[0009] Step S1: Place polyvinylpyrrolidone in a beaker, add ethylene glycol, and stir until a clear solution is formed. Add Bi(NO3)3·5H2O, TeO2 and 1g NaOH to the beaker and continue stirring until clear to form a precursor solution.

[0010] Step S2: Place the precursor solution in a reaction vessel lined with 100 mL of polytetrafluoroethylene, heat the reaction vessel, cool it after a preset heating time, transfer the solution in the reaction vessel to a centrifuge tube, centrifuge and collect it, wash and dry the centrifuged reactants to obtain Bi2Te3 nanosheets.

[0011] Step S3: Place Bi2Te3 nanosheets in deionized water and disperse them by ultrasonication to obtain a suspension. Add sodium dodecyl sulfonate to the suspension and perform magnetic stirring and ice bath stirring in sequence. After the ice bath stirring is completed, add a graphene oxide aqueous solution of a preset concentration and perform magnetic stirring and centrifugation to collect the precipitate in sequence. After washing and drying, Bi2Te3 / GO powder is obtained. The Bi2Te3 / GO powder is reduced to obtain Bi2Te3 / rGO.

[0012] Step S4: Take Bi2Te3 / rGO and put it into PEDOT:PSS solution treated with DMSO. After ultrasonic dispersion for a preset time, a mixed solution is formed. Cast the mixed solution into a film. After the film is cast, bake and impregnate in sequence to obtain a two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material.

[0013] Furthermore, in step S1, 50 mL of ethylene glycol is added and stirred vigorously until a clear solution is obtained. Then, 2 mmol Bi(NO3)3·5H2O, 3 mmol TeO2 and 1 g NaOH are added and stirred continuously until the solution is clear.

[0014] Furthermore, in step S2, an electric heating blower is used to heat the reaction vessel at a temperature of 190°C for 7 hours. When collecting the samples by centrifugation, the centrifuge speed is 7000 r / min.

[0015] Furthermore, in step S2, when washing and drying the centrifuged reaction product, acetone and deionized water are used for multiple washings, and the product is dried in a vacuum drying oven at a temperature of 65°C for 12 hours to obtain black powder Bi2Te3 nanosheets.

[0016] Further, in step S3, 0.1g of Bi2Te3 nanosheets are placed in 30 mL of deionized water and ultrasonically dispersed for 30 min; 0.018g of sodium dodecyl sulfonate is added to the suspension, and after magnetic stirring for 1.5 h, it is transferred to an ice bath stirrer at a temperature of 8°C. After ice bath stirring, 2-10 mL of graphene oxide aqueous solution with a preset concentration of 5 mg / mL is added and magnetically stirred. After magnetic stirring for 8 h, the precipitate is collected by centrifugation and washed. After washing, the precipitate is dried in a vacuum drying oven at 65°C.

[0017] Furthermore, in step S3, when reducing Bi2Te3 / GO powder, 2g of carbon powder and Bi2Te3 / GO powder are placed in the same ceramic boat for heat treatment. The heat treatment is carried out in a tube atmosphere furnace with a heating rate of 5℃ / min. After the temperature reaches 400℃, it is held for 1 hour. After cooling down with the furnace, Bi2Te3 / rGO is obtained.

[0018] Furthermore, in step S3, 10wt%-15wt% of Bi2Te3 / rGO is placed into a DMSO-treated PEDOT:PSS solution, ultrasonically dispersed for 30 min, and then stirred at room temperature for 8 h to form a mixed solution.

[0019] Furthermore, in step S3, when casting the mixed solution into a film, the film thickness is adjusted by setting the doctor blade height, and the mixed solution is uniformly coated on the substrate at a coating speed of 25 mm / s.

[0020] Furthermore, in step S3, after the casting film is completed, the substrate is placed in an oven at 60°C and kept at that temperature for 12 hours. After the solvent evaporates, a thin film is obtained. The film is then wetted with water and peeled off from the substrate. The film is then kept in an oven at 80°C for 4 hours to obtain a two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material with a thickness of micrometers and self-supporting properties.

[0021] In a second aspect, the present invention provides a two-dimensional flexible composite material, a two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material prepared based on the preparation method of the two-dimensional flexible composite material.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This application provides a two-dimensional flexible composite material and its preparation method. The method involves heat-treating Bi₂Te₃ nanosheets to increase crystallinity and enhance the electrical conductivity of the two-dimensional ternary composite material. The Bi₂Te₃ / rGO mixture is then placed in a DMSO-treated PEDOT:PSS solution, which generates an interfacial scattering effect, reducing the thermal conductivity of the composite material and improving its thermoelectric conversion efficiency. Furthermore, PEDOT serves as a flexible matrix, while Bi₂Te₃ is a rigid material, enabling the formation of an interfacial layer with a large specific surface area and strong adhesion in the rGO binary composite material. This not only improves the mechanical stability of the composite film but also allows the material to withstand repeated bending without compromising its thermoelectric properties. The preparation steps employed in this method are simple and easily scalable. The addition of sodium dodecyl sulfonate enhances the surface activity of the Bi₂Te₃ nanosheets, achieving surface modification and improving the interfacial compatibility between rGO, Bi₂Te₃, and PEDOT, thereby enhancing the overall performance and long-term stability of the composite material. Furthermore, by adding unequal amounts of graphene oxide aqueous solution, the electrical conductivity, Seebeck coefficient, and mechanical flexibility of the composite material can be flexibly controlled to meet the application requirements of different scenarios. The materials and methods used have a minimal environmental impact, adhering to the principles of composite green manufacturing and sustainable development. This invention systematically resolves the triangular contradiction of "performance-flexibility-cost" in flexible thermoelectric materials through precise control of rGO dosage, gas-phase reduction of CO, and reinforcement of the dual conductive network of PEDOT and rGO. Attached Figure Description

[0024] Figure 1 SEM images of Bi2Te3 nanosheets from embodiments of this disclosure are shown;

[0025] Figure 2 SEM images of Bi2Te3 / rGO in embodiments of this disclosure are shown;

[0026] Figure 3 TEM images of Bi2Te3 nanosheets and Bi2Te3 / rGO in embodiments of this disclosure are shown;

[0027] Figure 4 XRD images of Bi2Te3 / GO and Bi2Te3 / rGO from embodiments of this disclosure are shown;

[0028] Figure 5 A line graph showing the conductivity of the Bi2Te3 / rGO / PEDOT composite material as a function of temperature in an embodiment of this disclosure is shown.

[0029] Figure 6 A piecewise linear plot of the Seebeck coefficient as a function of temperature for the Bi2Te3 / rGO / PEDOT composite material in the embodiments of this disclosure is shown.

[0030] Figure 7 A line graph showing the power factor variation of the Bi2Te3 / rGO / PEDOT composite material in the embodiments of this disclosure as a function of temperature is shown. Detailed Implementation

[0031] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] Example 1

[0033] Step S1: Weigh polyvinylpyrrolidone and place it in a beaker. Add 50 mL of ethylene glycol and stir vigorously until a clear solution is obtained. Add 2 mmol Bi(NO3)3·5H2O, 3 mmol TeO2, and 1 g NaOH to the beaker and continue stirring until a clear precursor liquid is obtained. Transfer the precursor liquid to a reaction vessel lined with 100 mL of polytetrafluoroethylene and react at 190 °C for 7 h in an electrically heated blast oven. After the reaction is complete, cool the mixture and transfer it to centrifuge tubes. Centrifuge at 7000 r / min to collect the product. Wash the collected reaction mixture several times with acetone and deionized water, and then place it in a vacuum drying oven at 65 °C for 12 h. The resulting black powder is Bi2Te3 nanosheets. Figure 1 and Figure 3 As shown.

[0034] Step S2: Weigh 0.1g of Bi2Te3 nanosheets and place them in 30 mL of deionized water. Disperse by ultrasonication for 30 min to obtain a suspension. Weigh 0.018g of sodium dodecyl sulfonate and add it to the suspension. After magnetic stirring for 1.5 h, transfer to an ice bath stirrer. Set the ice bath stirring temperature to 8℃. Add 6 mL of a 5 mg / mL graphene oxide aqueous solution. After magnetic stirring for 8 h, centrifuge to collect the precipitate and wash it. Dry the washed precipitate in a vacuum drying oven at 65℃. After complete drying, the Bi2Te3 / GO powder undergoes reduction treatment. During reduction treatment, 2g of carbon powder and Bi2Te3 / GO powder are placed in the same ceramic boat for heat treatment. A tubular atmosphere furnace is used for heat treatment. The heating rate of the tubular atmosphere furnace is 5℃ / min. After reaching 400℃, hold for 1 h. After cooling with the furnace, Bi2Te3 / GO is converted to Bi2Te3 / rGO, as shown below. Figure 2 and Figure 3 As shown.

[0035] Figure 4The XRD images of Bi2Te3 / GO and Bi2Te3 / rGO in the embodiments of this disclosure are shown. As can be seen from the figure, the horizontal axis is twice the diffraction angle (2theta (degree)) in degrees, and the vertical axis is the intensity of the diffraction peak (Intensity (au)). It can be seen that compared with Bi2Te3 / GO, the diffraction peak of Bi2Te3 / rGO is significantly higher and sharper, indicating that the crystallinity of Bi2Te3 / rGO is significantly higher than that of Bi2Te3 / GO. This suggests that the carbon powder-based reduction process is more conducive to the growth and orderly arrangement of Bi2Te3 grains.

[0036] Step S3: Weigh 15wt% Bi2Te3 / rGO and add a DMSO-treated PEDOT:PSS solution. After ultrasonic dispersion for 30 min, stir at room temperature for 8 h. After uniform mixing, cast into a film. Adjust the film thickness by setting the doctor blade height and coat it onto the substrate at a coating speed of 25 mm / s. After casting, transfer it to a 60℃ oven and keep it at that temperature for 12 h. After the solvent evaporates, a film is obtained. After wetting the film with water, peel it off from the substrate and keep it at 80℃ for 4 h to obtain a micron-thick, self-supporting, two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material.

[0037] Figure 5 A line graph showing the conductivity of the Bi2Te3 / rGO / PEDOT composite material as a function of temperature in embodiments of this disclosure is shown, as follows. Figure 5 As shown, the horizontal axis represents temperature (K) and the vertical axis represents electrical conductivity (S / cm). It can be seen that the two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material in this embodiment has a high carrier concentration, is less affected by the negative impact of temperature, and maintains a high overall electrical conductivity. Figure 6 The figure shows a piecewise linear plot of the Seebeck coefficient of the Bi2Te3 / rGO / PEDOT composite material in the embodiments of this disclosure as a function of temperature, as follows: Figure 6 As shown, the horizontal axis represents temperature (K), and the vertical axis represents the Seebeck coefficient (mV / K). It can be seen that the Seebeck coefficient increases with increasing temperature. Increasing temperature is beneficial to increasing the thermoelectric potential of the material. When the temperature increases, the carrier energy distribution near the Fermi level is wider, which leads to an increase in the voltage difference generated by the temperature difference. Figure 7 A line graph showing the power factor variation of the Bi2Te3 / rGO / PEDOT composite material as a function of temperature in embodiments of this disclosure is shown, as follows: Figure 7As shown, the horizontal axis represents temperature (K) and the vertical axis represents power factor (mW / mK²). It can be seen that although the conductivity decreases slightly with temperature, the significant increase in the Seebeck coefficient completely offsets the negative impact of conductivity, and the power factor ultimately increases significantly with increasing temperature.

[0038] Example 2

[0039] Step S1: Weigh polyvinylpyrrolidone and place it in a beaker. Add 50 mL of ethylene glycol and stir vigorously until a clear solution is obtained. Add 2 mmol Bi(NO3)3·5H2O, 3 mmol TeO2, and 1 g NaOH to the beaker and continue stirring until a clear precursor liquid is obtained. Transfer the precursor liquid to a reaction vessel lined with 100 mL of polytetrafluoroethylene and react at 190 °C for 7 h in an electrically heated blast oven. After the reaction is complete, cool the mixture and transfer it to a centrifuge tube. Centrifuge at 7000 r / min to collect the product. Wash the collected reaction mixture several times with acetone and deionized water, and then place it in a vacuum drying oven at 65 °C for 12 h. The resulting black powder is Bi2Te3 nanosheets.

[0040] Step S2: Weigh 0.1 g of Bi₂Te₃ nanosheets and place them in 30 mL of deionized water. Disperse by ultrasonication for 30 min to obtain a suspension. Weigh 0.018 g of sodium dodecyl sulfate and add it to the suspension. After magnetic stirring for 1.5 h, transfer the mixture to an ice bath stirrer. Set the ice bath stirring temperature to 8 °C. Add 2 mL of a 5 mg / mL graphene oxide aqueous solution. After magnetic stirring for 8 h, centrifuge to collect the precipitate and wash it. Dry the washed precipitate in a vacuum drying oven at 65 °C. After the Bi₂Te₃ / GO powder is completely dried, it undergoes reduction treatment. During reduction treatment, 2 g of carbon powder and Bi₂Te₃ / GO powder are placed in the same ceramic boat for heat treatment. A tubular atmosphere furnace is used for heat treatment. The heating rate of the tubular atmosphere furnace is 5 °C / min. After reaching 400 °C, hold for 1 h. After cooling with the furnace, Bi₂Te₃ / GO is converted to Bi₂Te₃ / rGO.

[0041] Step S3: Weigh 15wt% Bi2Te3 / rGO and add a DMSO-treated PEDOT:PSS solution. After ultrasonic dispersion for 30 min, stir at room temperature for 8 h. After uniform mixing, cast into a film. Adjust the film thickness by setting the doctor blade height and coat it onto the substrate at a coating speed of 25 mm / s. After casting, transfer it to a 60℃ oven and keep it at that temperature for 12 h. After the solvent evaporates, a film is obtained. After wetting the film with water, peel it off from the substrate and keep it at 80℃ for 4 h to obtain a micron-thick, self-supporting, two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material.

[0042] Example 3

[0043] Step S1: Weigh polyvinylpyrrolidone and place it in a beaker. Add 50 mL of ethylene glycol and stir vigorously until a clear solution is obtained. Add 2 mmol Bi(NO3)3·5H2O, 3 mmol TeO2, and 1 g NaOH to the beaker and continue stirring until a clear precursor liquid is obtained. Transfer the precursor liquid to a reaction vessel lined with 100 mL of polytetrafluoroethylene and react at 190 °C for 7 h in an electrically heated blast oven. After the reaction is complete, cool the mixture and transfer it to a centrifuge tube. Centrifuge at 7000 r / min to collect the product. Wash the collected reaction mixture several times with acetone and deionized water, and then place it in a vacuum drying oven at 65 °C for 12 h. The resulting black powder is Bi2Te3 nanosheets.

[0044] Step S2: Weigh 0.1 g of Bi₂Te₃ nanosheets and place them in 30 mL of deionized water. Disperse by ultrasonication for 30 min to obtain a suspension. Weigh 0.018 g of sodium dodecyl sulfate and add it to the suspension. After magnetic stirring for 1.5 h, transfer the mixture to an ice bath stirrer at 8 °C. Add 10 mL of a 5 mg / mL graphene oxide aqueous solution. After magnetic stirring for 8 h, centrifuge to collect the precipitate and wash it. Dry the washed precipitate in a vacuum drying oven at 65 °C. After complete drying, the Bi₂Te₃ / GO powder undergoes reduction treatment. During reduction, 2 g of carbon powder and Bi₂Te₃ / GO powder are placed in the same ceramic boat for heat treatment. A tubular atmosphere furnace is used for heat treatment at a heating rate of 5 °C / min. After reaching 400 °C, hold for 1 h. After cooling in the furnace, Bi₂Te₃ / GO is converted to Bi₂Te₃ / rGO.

[0045] Step S3: Weigh 15wt% Bi2Te3 / rGO and add a DMSO-treated PEDOT:PSS solution. After ultrasonic dispersion for 30 min, stir at room temperature for 8 h. After uniform mixing, cast into a film. Adjust the film thickness by setting the doctor blade height and coat it onto the substrate at a coating speed of 25 mm / s. After casting, transfer it to a 60℃ oven and keep it at that temperature for 12 h. After the solvent evaporates, a film is obtained. After wetting the film with water, peel it off from the substrate and keep it at 80℃ for 4 h to obtain a micron-thick, self-supporting, two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material.

Claims

1. A method for preparing a two-dimensional flexible composite material, characterized in that, Includes the following steps: Step S1: Place polyvinylpyrrolidone in a beaker, add ethylene glycol, and stir until a clear solution is formed. Add Bi(NO3)3·5H2O, TeO2 and 1g NaOH to the beaker and continue stirring until clear to form a precursor solution. Step S2: Place the precursor solution in a reaction vessel lined with 100 mL of polytetrafluoroethylene, heat the reaction vessel, cool it after a preset heating time, transfer the solution in the reaction vessel to a centrifuge tube, centrifuge and collect it, wash and dry the centrifuged reactants to obtain Bi2Te3 nanosheets. Step S3: Place Bi2Te3 nanosheets in deionized water and disperse them by ultrasonication to obtain a suspension. Add sodium dodecyl sulfonate to the suspension and perform magnetic stirring and ice bath stirring in sequence. After the ice bath stirring is completed, add a graphene oxide aqueous solution of a preset concentration and perform magnetic stirring and centrifugation to collect the precipitate in sequence. After washing and drying, Bi2Te3 / GO powder is obtained. The Bi2Te3 / GO powder is reduced to obtain Bi2Te3 / rGO. Step S4: Take Bi2Te3 / rGO and put it into PEDOT:PSS solution treated with DMSO. After ultrasonic dispersion for a preset time, a mixed solution is formed. Cast the mixed solution into a film. After the film is cast, bake and impregnate in sequence to obtain a two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material.

2. The method for preparing the two-dimensional flexible composite material according to claim 1, characterized in that, In step S1, 50 mL of ethylene glycol is added and stirred vigorously until a clear solution is obtained. Then, 2 mmol Bi(NO3)3·5H2O, 3 mmol TeO2 and 1 g NaOH are added and stirred continuously until the solution is clear.

3. The method for preparing the two-dimensional flexible composite material according to claim 1, characterized in that, In step S2, the reactor is heated by an electric heating box at a temperature of 190°C for 7 hours. When collecting the samples by centrifugation, the centrifuge speed is 7000 r / min.

4. The method for preparing the two-dimensional flexible composite material according to claim 3, characterized in that, In step S2, when washing and drying the centrifuged reactants, acetone and deionized water are used for multiple washings. The drying is carried out in a vacuum drying oven at a temperature of 65°C for 12 hours to obtain black Bi2Te3 nanosheets.

5. The method for preparing the two-dimensional flexible composite material according to claim 1, characterized in that, In step S3, 0.1 g of Bi2Te3 nanosheets were placed in 30 mL of deionized water and ultrasonically dispersed for 30 min. 0.018 g of sodium dodecyl sulfonate was added to the suspension and magnetically stirred for 1.5 h. The mixture was then transferred to an ice bath stirrer at 8 °C. After ice bath stirring, 2-10 mL of a graphene oxide aqueous solution with a preset concentration of 5 mg / mL was added and magnetically stirred for 8 h. The precipitate was collected by centrifugation and washed. After washing, the precipitate was dried in a vacuum drying oven at 65 °C.

6. The method for preparing the two-dimensional flexible composite material according to claim 5, characterized in that, In step S3, when reducing Bi2Te3 / GO powder, 2g of carbon powder and Bi2Te3 / GO powder are placed in the same ceramic boat for heat treatment. The heat treatment is carried out in a tube atmosphere furnace with a heating rate of 5℃ / min. After the temperature reaches 400℃, it is held for 1 hour. After cooling down with the furnace, Bi2Te3 / rGO is obtained.

7. The method for preparing the two-dimensional flexible composite material according to claim 1, characterized in that, In step S3, 10wt%-15wt% of Bi2Te3 / rGO is placed into a DMSO-treated PEDOT:PSS solution, ultrasonically dispersed for 30 min, and then stirred at room temperature for 8 h to form a mixed solution.

8. The method for preparing the two-dimensional flexible composite material according to claim 7, characterized in that, In step S3, when casting the mixed solution into a film, the film thickness is adjusted by setting the doctor blade height, and the mixed solution is uniformly coated on the substrate at a coating speed of 25 mm / s.

9. The method for preparing the two-dimensional flexible composite material according to claim 8, characterized in that, In step S3, after the film is cast, the substrate is placed in an oven at 60°C and kept at that temperature for 12 hours. After the solvent evaporates, a thin film is obtained. The film is then wetted with water and peeled off from the substrate. The film is then kept in an oven at 80°C for 4 hours to obtain a two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material with a thickness of micrometers and self-supporting properties.

10. A two-dimensional flexible composite material, characterized in that, The two-dimensional flexible Bi2Te3 / rGO / PEDOT composite material was prepared by the preparation method of the two-dimensional flexible composite material according to any one of claims 1-9.

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