A method for preparing high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric films

Abstract

This invention relates to a method for preparing a high-performance flexible composite thermoelectric film of polypyrrole / silver selenide / nylon, comprising the following steps: (1) using selenium nanowires as a template, reacting them with silver nitrate in ethylene glycol solvent to obtain silver selenide nanostructures, then adding pyrrole monomers, sonicating, followed by adding ammonium persulfate, stirring at room temperature, and in-situ polymerization on the silver selenide nanostructures to synthesize polypyrrole / silver selenide nanostructures; (2) dispersing the polypyrrole / silver selenide nanostructures in anhydrous ethanol, filtering, and vacuum drying to obtain the polypyrrole / silver selenide / nylon composite film. The method of this invention can be used to prepare high-performance flexible thermoelectric films, and these films can be used to fabricate high-output thermoelectric devices to power wearable electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of flexible thermoelectric thin film technology, and relates to a method for preparing high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric thin films. Background Technology

[0002] Thermoelectric materials are a class of functional materials that can directly convert heat energy into electrical energy and vice versa. Thermoelectric power generation and refrigeration devices made from thermoelectric materials have advantages such as simple structure, small size, no wear, no noise, and no pollution. As environmentally friendly materials, thermoelectric materials have broad application prospects.

[0003] The performance of thermoelectric materials is generally measured by the dimensionless figure of merit ZT, which is expressed as follows:

[0004] ZT=α 2 σT / κ, where: α is the Seebeck coefficient; σ is the electrical conductivity; κ is the thermal conductivity; and T is the thermodynamic temperature. For thin film materials, the power factor PF (PF = α) is commonly used. 2 Its thermoelectric properties are measured by σ).

[0005] Flexible thermoelectric materials have received increasing attention and made some progress in recent years, especially organic materials and their composite thermoelectric materials. Conductive polymers have advantages such as good flexibility, ease of processing, and low thermal conductivity, but their power factor is relatively low. Therefore, most studies use conductive polymers as the matrix in composite thermoelectric materials, with inorganic materials as fillers, to improve the thermoelectric performance of the composite material through the synergistic effect between the two phases. However, traditional organic / inorganic composite methods suffer from problems such as poor dispersibility and excessive organic phases, resulting in poor film performance. In addition, due to the rigid nature of inorganic thermoelectric materials, they usually cannot meet the flexibility requirements on their own. Besides composites with organic polymers, the method of using flexible materials as substrates to support inorganic thermoelectric materials is also attracting increasing attention.

[0006] Silver selenide is a narrow bandgap semiconductor (0K, bandgap of 0.07 eV) and undergoes a phase transition at 407 K. The low-temperature phase of silver selenide has an orthorhombic structure and exhibits semiconductor properties, while the high-temperature phase has a cubic structure and is a superionic conductor. The low-temperature phase of silver selenide possesses high electrical conductivity, a relatively high Seebeck coefficient, and low thermal conductivity, resulting in excellent thermoelectric properties near room temperature. However, most currently prepared silver selenide materials are non-flexible, limiting their application in flexible thermoelectric materials.

[0007] The patent "A Preparation Method for Optimizing the Thermoelectric Properties of Silver Selenide / Nylon Flexible Composite Film" (Publication No.: CN110828651A) describes the synthesis of a non-uniform one-dimensional silver selenide nanostructure using a wet chemical method at 40℃. Using a flexible nylon filter membrane as a substrate, a silver selenide film with a certain degree of flexibility was obtained through vacuum filtration and hot pressing (200℃, 1MPa). This film achieves a power factor of 1882 μW / m² at room temperature. -1 K -2 Its ZT value is as high as 0.8, which is one of the highest-performing flexible thermoelectric films reported to date. However, its power factor is still some distance from that of non-flexible silver selenide films. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric films, so as to further optimize the thermoelectric properties of flexible composite thermoelectric films.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric film includes the following steps:

[0011] (1) First, using selenium nanowires as templates, silver nitrate was reacted with ethylene glycol solvent to obtain silver selenide nanostructures. Then, pyrrole monomers were added and sonicated. Subsequently, ammonium persulfate was added and stirred at room temperature. The purpose was to enable the pyrrole monomers to polymerize in situ on the silver selenide nanostructures to form polypyrrole, thus synthesizing polypyrrole / silver selenide nanostructures.

[0012] (2) Disperse the polypyrrole / silver selenide nanostructure in anhydrous ethanol, filter, and dry under vacuum to obtain the polypyrrole / silver selenide / nylon composite film.

[0013] Furthermore, the selenium nanowires are synthesized using selenium dioxide as the selenium source and ascorbic acid as the reducing agent.

[0014] Furthermore, the ratio of selenium nanowires to pyrrole monomers is 0.5 mmol:(1-3) μL, preferably 0.5 mmol:1 μL.

[0015] Furthermore, the molar ratio of selenium nanowires to silver nitrate is 1 to 3:1, preferably 2:1.

[0016] Furthermore, the molar ratio of ammonium persulfate to pyrrole monomer is 4 to 6:1, preferably 5:1.

[0017] Furthermore, the reaction temperature of selenium nanowires with silver nitrate is 40℃, and the reaction time is 1.5 to 2.5 h.

[0018] Furthermore, after adding ammonium persulfate, the mixture should be stirred at room temperature for 10–30 minutes.

[0019] Furthermore, the centrifugation conditions for the in-situ polymerization product are as follows: centrifuge at 4000 r / min for 2-4 min, remove the supernatant, and then alternately add ethanol and deionized water to the centrifuge tube, and continue to centrifuge at 4000 r / min for 2-4 min to remove impurities.

[0020] Furthermore, in step (2), the filtration process specifically involves using a vacuum filtration method with a nylon filter membrane as a substrate to form a film.

[0021] Furthermore, in step (2), the vacuum drying temperature is 50-60℃ and the time is 10-12h.

[0022] Furthermore, the obtained polypyrrole / silver selenide / nylon composite film is further subjected to hot pressing treatment.

[0023] Furthermore, the specific hot-pressing process conditions are: hot pressing at 230℃ and 1-4MPa for 30 minutes.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The preparation process is simple, easy to implement and low-cost, and low-temperature, short-time heat treatment is used, which saves energy;

[0026] (2) Polypyrrole, which is cheaper, non-toxic and has fewer reports on thermoelectric properties compared to other conductive polymers, was selected as the matrix in the composite material. The organic and inorganic phases were effectively combined through simple in-situ polymerization.

[0027] (3) Through hot pressing at a lower temperature and lower pressure, well-crystallized silver selenide grains with continuous grain boundaries are formed inside the film, which improves the conductivity; at the same time, the addition of polypyrrole further regulates the orientation of the silver selenide grains, which is also conducive to improving the conductivity.

[0028] (4) The introduction of heterostructures between silver selenide and selenium nanocrystals and between silver selenide and polypyrrole enhances phonon scattering inside the film, reduces the thermal conductivity of the film, and generates an energy filtering effect, which to some extent improves the Seebeck coefficient and enhances the overall thermoelectric performance of the film.

[0029] (5) The addition of polypyrrole further optimizes the flexibility of the composite film, which is more conducive to the application of wearable devices. Attached Figure Description

[0030] Figure 1The image shows an XRD comparison of the hot-pressed polypyrrole / silver selenide / nylon flexible composite film (AP1) prepared by this invention and the existing silver selenide / nylon flexible composite film (AP0).

[0031] Figure 2 Comparison of thermoelectric properties of hot-pressed composite films obtained by adding different volumes (1, 2, 3 μL) of pyrrole monomer.

[0032] Figure 3 The thermal conductivity and ZT value of the hot-pressed polypyrrole / silver selenide / nylon flexible composite film (AP1) prepared by this invention are compared with those of the existing silver selenide / nylon flexible composite film (AP0).

[0033] Figure 4 These are transmission electron microscope (TEM) images at different magnifications of the polypyrrole-coated multiscale silver selenide nanostructures prepared in this invention.

[0034] Figure 5 SEM comparison images of (a,b) hot-pressed polypyrrole / silver selenide / nylon flexible composite film (AP0) and (c,d) hot-pressed silver selenide / nylon flexible composite film (AP1).

[0035] Figure 6 The graph shows the change in power factor of a hot-pressed polypyrrole / silver selenide / nylon flexible composite film (AP1) after being bent at different times with a bending radius of 4 mm. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0037] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0038] Example 1:

[0039] A method for preparing a high-performance silver selenide / polypyrrole / nylon flexible composite thermoelectric film is disclosed. The method involves dispersing 0.5 mmol of selenium nanowires in 100 mL of ethylene glycol solution, adding 0.17 g of silver nitrate (the amount added satisfies a molar ratio of silver nitrate to selenium nanowires of 2:1) to a beaker, stirring at 40 °C for 2 h, adding 1 μL of pyrrole monomer, sonicating for 30 min, and then adding ammonium persulfate as an oxidant (the amount added satisfies a molar ratio of pyrrole monomer to ammonium persulfate of 1:5). The purpose of adding ammonium persulfate is to polymerize the pyrrole monomer in situ into polypyrrole. The mixture was stirred at room temperature for 20 min, centrifuged at 4000 rpm to extract the black precipitate. The precipitate was then washed by alternating addition of deionized water and anhydrous ethanol, centrifuged at 4000 rpm for 3 min to remove impurities. After centrifugation, the carefully washed black target product was dispersed in 30 ml of anhydrous ethanol and ultrasonically dispersed for 15 min. Then, using a nylon filter membrane as a substrate, vacuum filtration was performed to obtain a silver selenide / polypyrrole / nylon flexible thermoelectric membrane. The obtained membrane was dried in a vacuum drying oven at 60 °C for 12 h. After removing the membrane, it was hot-pressed at 230 °C and 1 MPa for 30 min, yielding a power factor of approximately 2240 μW / m². -1 K -2 Silver selenide / nylon flexible composite film. Figure 1 This is the XRD pattern of a hot-pressed polypyrrole / silver selenide / nylon flexible composite film. The peak energy of silver selenide corresponds well with the standard card. In addition, there is also a selenium peak (corresponding to selenium nanoparticles). The presence of selenium inclusions is beneficial for enhancing phonon scattering, and the heterojunction produces an energy filtering effect, which to some extent improves the Seebeck coefficient of the sample. Figure 3 As can be seen, compared with the silver selenide / nylon flexible composite film (AP0) obtained in patent CN110828651A, the (112) and (210) peaks of the hot-pressed film are enhanced after the addition of polypyrrole in this preparation method. This difference indicates that polypyrrole can change the orientation of Ag2Se grains.

[0040] Comparative Example 1

[0041] Most of the results were the same as in Example 1, except that the amount of polypyrrole added was changed from 1 μL to 3 μL.

[0042] Figure 2 The thermoelectric properties of hot-pressed polypyrrole / silver selenide / nylon flexible composite films prepared by adding different volumes of polypyrrole are shown. It can be seen that when the amount of polypyrrole added is 3μL, compared with Example 1, the Seebeck coefficient of the hot-pressed composite film is slightly improved, while the electrical conductivity decreases, resulting in a decrease in the overall power factor.

[0043] Figure 4These are transmission electron microscope (TEM) images at different magnifications of the polypyrrole-coated silver selenide nanostructures prepared in Example 1. The surface of these non-uniform silver selenide nanostructures is coated with polypyrrole that is several nanometers thick.

[0044] Figure 5 This is a SEM image of the hot-pressed polypyrrole / silver selenide / nylon flexible composite film prepared in Example 1, wherein... Figure 5 (b) is Figure 5 (a) shows a magnified view of the prepared composite film, which is very dense with many triangular grain boundaries and many flocculent structures on the surface. Based on the analysis, it is inferred that it is polypyrrole.

[0045] Figure 6 The graph shows the change in power factor of a hot-pressed polypyrrole / silver selenide / nylon flexible composite film (AP1) after being bent at different times with a bending radius of 4 mm.

[0046] Example 2:

[0047] A method for preparing a high-performance silver selenide / polypyrrole / nylon flexible composite thermoelectric film is disclosed. The method involves dispersing 0.5 mmol of selenium nanowires in 100 mL of ethylene glycol solution, adding 0.17 g of silver nitrate (the amount added satisfies a molar ratio of silver nitrate to selenium nanowires of 2:1) to a beaker, stirring at 40 °C for 2 h, adding 2 μL of pyrrole monomer, sonicating for 30 min, and then adding ammonium persulfate as an oxidant (the amount added satisfies a molar ratio of pyrrole to ammonium persulfate of 1:5). The purpose of adding ammonium persulfate is to polymerize the pyrrole monomer in situ into polypyrrole. The mixture was stirred at room temperature for 20 min, then centrifuged at 4000 rpm to extract the black precipitate. The precipitate was then washed by alternating addition of deionized water and anhydrous ethanol, centrifuged at 4000 rpm for 3 min to remove impurities. After centrifugation, the carefully washed black target product was dispersed in 30 ml of anhydrous ethanol and ultrasonically dispersed for 15 min. Then, using a nylon filter membrane as a substrate, vacuum filtration was performed to obtain a silver selenide / polypyrrole / nylon flexible thermoelectric membrane. The obtained membrane was placed in a vacuum drying oven and dried at 60 °C for 12 h. After removing the membrane, it was hot-pressed at 230 °C and 1 MPa for 30 min to obtain a polypyrrole / silver selenide / nylon flexible composite film.

[0048] Example 3:

[0049] A method for preparing a high-performance silver selenide / polypyrrole / nylon flexible composite thermoelectric film is disclosed. The method involves dispersing 0.5 mmol of selenium nanowires in 100 mL of ethylene glycol solution, adding 0.17 g of silver nitrate (the amount added satisfies a molar ratio of silver nitrate to selenium nanowires of 2:1) to a beaker, stirring at 40 °C for 2 h, adding 3 μL of pyrrole monomer, sonicating for 30 min, and then adding ammonium persulfate as an oxidant (the amount added satisfies a molar ratio of pyrrole to ammonium persulfate of 1:5). The purpose of adding ammonium persulfate is to polymerize the pyrrole monomer in situ into polypyrrole. The mixture was stirred at room temperature for 20 min, centrifuged at 4000 rpm, and the resulting black precipitate was extracted. The precipitate was then washed by alternating addition of deionized water and anhydrous ethanol, centrifuged at 4000 rpm for 3 min to remove impurities. After centrifugation, the carefully washed black target product was dispersed in 30 ml of anhydrous ethanol and ultrasonically dispersed for 15 min. Then, using a nylon filter membrane as a substrate, vacuum filtration was performed to obtain a silver selenide / polypyrrole / nylon flexible thermoelectric membrane. The obtained membrane was placed in a vacuum drying oven and dried at 60 °C for 12 h. After removing the membrane, it was hot-pressed at 230 °C and 1 MPa for 30 min to obtain a polypyrrole / silver selenide / nylon flexible composite film.

[0050] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric film, characterized in that, Includes the following steps: (1) First, using selenium nanowires as templates, silver selenide nanostructures were obtained by reacting with silver nitrate in ethylene glycol solvent. Then, pyrrole monomers were added, and the mixture was sonicated. Subsequently, ammonium persulfate was added and stirred at room temperature to polymerize in situ on the silver selenide nanostructures to synthesize polypyrrole / silver selenide nanostructures. (2) Disperse the polypyrrole / silver selenide nanostructure in anhydrous ethanol, filter, and vacuum dry to obtain the polypyrrole / silver selenide / nylon composite film; The ratio of selenium nanowires to pyrrole monomers was 0.5 mmol: 1 μL; The molar ratio of ammonium persulfate to pyrrole monomer is 4~6:1; The molar ratio of silver nitrate to selenium nanowires is 2:1; The reaction temperature of selenium nanowires with silver nitrate is 40℃, and the reaction time is 1.5~2.5h. After adding ammonium persulfate, stir at room temperature for 10-30 minutes.

2. The method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric thin film according to claim 1, characterized in that, In step (2), the filtration process is specifically as follows: using vacuum filtration with a nylon filter membrane as a substrate to form a film.

3. The method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric film according to claim 1, characterized in that, In step (2), the vacuum drying temperature is 50~60℃ and the time is 10~12h.

4. The method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric film according to claim 1, characterized in that, The resulting polypyrrole / silver selenide / nylon composite film is further subjected to hot pressing treatment.

5. The method for preparing a high-performance polypyrrole / silver selenide / nylon flexible composite thermoelectric film according to claim 4, characterized in that, The specific hot pressing process conditions are: hot pressing at 230℃ and 1-4 MPa for 30 min.

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