Preparation method of silver selenide three-dimensional structure thermoelectric material

Abstract

The invention relates to the technical field of thermoelectric material preparation, in particular to a preparation method of a silver selenide three-dimensional structure thermoelectric material, which comprises the following steps: providing a three-dimensional substrate; performing conductive treatment on the surface of the three-dimensional substrate to obtain a conductive substrate; preparing an electroplating solution by using silver nitrate, taking the conductive substrate as a cathode and elemental silver as an anode, and immersing the elemental silver and the conductive substrate into the electroplating solution for electroplating to obtain a silver-plated substrate; a selenium solution is prepared, the silver-plated substrate is added into the selenium solution to be soaked, and the silver selenide three-dimensional structure thermoelectric material is obtained. Through the method provided by the invention, the loading capacity of silver selenide in the three-dimensional structure thermoelectric material can be improved, and the effect of improving the thermoelectric performance of the silver selenide three-dimensional structure thermoelectric material is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of thermoelectric material preparation, and in particular to a method for preparing a silver selenide three-dimensional structure thermoelectric material. Background Art

[0002] Silver selenide has excellent thermoelectric properties. Compared with the most widely used Bi-Te-based thermoelectric materials, the constituent elements of silver selenide, which belongs to the metal oxide family, have higher abundance, lower cost, and lower toxicity.

[0003] However, current research on silver selenide-based thermoelectric materials in the field of wearable devices is mainly focused on two-dimensional thin-film-based thermoelectric devices. However, it is difficult for thin-film materials to establish an effective temperature difference, and there are few reports on three-dimensional structured thermoelectric materials that can establish a temperature difference. In addition, since silver plating based on three-dimensional structured thermoelectric materials usually adopts chemical plating method, the silver selenide loading of existing three-dimensional structured thermoelectric materials is relatively small, making it difficult for them to have excellent thermoelectric properties. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present application provides a method for preparing a three-dimensional structured silver selenide thermoelectric material, which can increase the loading amount of silver selenide in the three-dimensional structured thermoelectric material.

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is: to provide a method for preparing a three-dimensional structure thermoelectric material of silver selenide, including providing a three-dimensional substrate; conducting a surface of the three-dimensional substrate to obtain a conductive substrate; preparing an electroplating solution using silver nitrate, using the conductive substrate as a cathode and elemental silver as an anode, immersing the elemental silver and the conductive substrate in the electroplating solution for electroplating to obtain a silver-plated substrate; preparing a selenium solution, adding the silver-plated substrate into the selenium solution for immersion, and obtaining a three-dimensional structure thermoelectric material of silver selenide.

[0006] In a specific embodiment, the conductive treatment of the surface of the three-dimensional matrix includes: preparing a reducing agent solution and a silver ammonia solution; mixing the reducing agent solution with the silver ammonia solution to obtain a first mixed solution; completely immersing the three-dimensional matrix in the first mixed solution, and plating silver on the surface of the three-dimensional matrix.

[0007] In a specific embodiment, the preparation of the reducing agent solution includes: dissolving a main reducing agent, an auxiliary reducing agent, a dispersant and a co-solvent in deionized water to obtain the reducing agent solution; wherein the main reducing agent and the auxiliary reducing agent are used to reduce the silver ions in the silver ammonia solution, the dispersant is used to disperse the silver element reduced by the silver ions, and the co-solvent is used to dissolve the dispersant.

[0008] In a specific embodiment, the main reducing agent includes glucose monohydrate, the auxiliary reducing agent includes potassium sodium tartrate tetrahydrate, the surfactant includes polyethylene glycol, and the cosolvent includes ethanol; wherein, the mass ratio of the glucose monohydrate, the potassium sodium tartrate tetrahydrate, the polyethylene glycol, and the ethanol is (35-45):(10-20):(0.1-1):(100-150).

[0009] In a specific embodiment, the completely immersing the three-dimensional matrix into the first mixed solution includes: immersing the three-dimensional matrix into the first mixed solution, and squeezing the three-dimensional matrix until the residual bubbles in the three-dimensional matrix are extruded.

[0010] In a specific embodiment, the preparing the electroplating solution using silver nitrate includes: mixing a silver nitrate solution and a potassium metabisulfite solution to obtain a second mixed solution; immediately adding the second mixed solution into a sodium thiosulfate solution to obtain a third mixed solution; adding a pH buffer and a brightening agent into the third mixed solution to obtain the electroplating solution.

[0011] In a specific embodiment, the pH buffer includes ammonium acetate, and the brightening agent includes thiosemicarbazide; wherein, the mass ratio of silver nitrate in the silver nitrate solution, potassium metabisulfite in the potassium metabisulfite solution, sodium thiosulfate in the sodium thiosulfate solution, ammonium acetate, and thiosemicarbazide is (40-50):(20-30):(200-250):(20-30):(0.1-1).

[0012] In a specific embodiment, the electroplating by immersing the elemental silver and the conductive matrix into the electroplating solution includes: immersing the elemental silver and the conductive matrix into the electroplating solution, and electroplating for 1-4 hours under the conditions of a current of 0.018-0.04 A, a stirring rotor speed of 300-500 rpm, and a temperature of 25-35 °C.

[0013] In a specific embodiment, the preparing the selenium solution includes: dissolving sodium sulfide nonahydrate using deionized water, and then adding selenium to obtain the selenium solution; wherein, the mass ratio of the sodium sulfide nonahydrate to the selenium is (2.5-3.5):(0.5-1.5).

[0014] In a specific embodiment, the providing the three-dimensional matrix includes: soaking a matrix raw material in a sodium hydroxide solution with a concentration of 70-90 g / L for 30-60 minutes; washing the matrix raw material with deionized water and drying it to obtain the three-dimensional matrix; wherein, the three-dimensional matrix includes at least one of melamine sponge, polyurethane sponge, lignin fiber, and nylon fiber.

[0015] The beneficial effects of the present application are as follows: Compared with the prior art, in the implementation mode of the present application, the three-dimensional matrix is first conductivized to enable it to conduct current. On this basis, with the conductive matrix as the cathode and elemental silver as the anode, silver is plated on the surface of the conductive matrix by an electrochemical method in the electroplating solution. Compared with the common electroless plating method, a larger silver loading amount can be applied in a single silver plating process. The electrochemical silver plating method has a higher plating speed, and the utilization rate of silver as the plating raw material is also higher, which can effectively increase the loading amount of silver selenide in the three-dimensional structure thermoelectric material, and thus achieve the effect of improving the thermoelectric performance of the silver selenide three-dimensional structure thermoelectric material. Description of the Drawings

[0016] Figure 1 It is a statistical chart of the conductivity of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0017] Figure 2 It is a statistical chart of the Seebeck coefficient of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0018] Figure 3 It is a statistical chart of the power factor of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0019] Figure 4 It is a statistical chart of the thermal conductivity of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0020] Figure 5 It is a statistical chart of the figure of merit of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0021] Figure 6 It is a statistical chart of the mechanical and electrical properties of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0022] Figure 7 It is an electron microscope image of the first embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0023] Figure 8 It is an electron microscope image of the second embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0024] Figure 9 It is an electron microscope image of the third embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0025] Figure 10 It is an electron microscope image of the fourth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0026] Figure 11 It is the electron microscope image of the fifth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0027] Figure 12 It is the electron microscope image of another position of the second embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0028] Figure 13 It is the electron microscope image of the sixth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0029] Figure 14 It is the electron microscope image of the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0030] Figure 15 It is the phase statistical chart of the fifth embodiment, the second embodiment, the sixth embodiment, and the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application;

[0031] Figure 16 It is the flow schematic block diagram of the embodiment of the preparation method of the silver selenide three-dimensional structure thermoelectric material of the present application. Detailed implementation manners

[0032] In the present application, the terms "arrange", "be provided with", and "connect" shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can be internal communication between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0033] The orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0035] Moreover, in addition to being used to represent orientation or positional relationships, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0036] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further elaborates on this application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0037] Silver selenide has excellent thermoelectric properties. Compared with the currently most widely used Bi-Te-based thermoelectric materials, the constituent elements of silver selenide, which belongs to metal chalcogenide compounds, have higher abundances, lower costs, and lower toxicity.

[0038] However, current research on silver selenide-based thermoelectric materials in the field of wearable devices mainly focuses on two-dimensional thin-film-based thermoelectric devices. However, it is difficult to establish an effective temperature difference in thin-film materials, and there are few reports on three-dimensional structure thermoelectric materials that can establish a temperature difference. Moreover, since silver plating on three-dimensional structure thermoelectric materials usually uses electroless plating methods, the silver selenide loading of existing three-dimensional structure thermoelectric materials is small, making it difficult for them to have excellent thermoelectric properties.

[0039] In order to improve or solve the above technical problems, the inventors of this application have conducted long-term research and proposed at least the following embodiments.

[0040] Please refer to Figure 16 , Figure 16 which is a flowchart showing an embodiment of the method for preparing a three-dimensional structure silver selenide thermoelectric material of this application. It should be noted that if there are substantially the same results, this embodiment is not limited to the Figure 16 shown process sequence. As Figure 16 shown, this embodiment includes:

[0041] S100: Provide a three-dimensional matrix.

[0042] Compared with thin films and quantum dots, three-dimensional matrices usually have larger volumes and complex microstructures, can accommodate more material components, and are suitable for constructing macroscopic thermoelectric devices. Due to their volume characteristics, thermoelectric materials based on three-dimensional matrices can easily establish a relatively high effective temperature difference. In the embodiments of this application, the three-dimensional matrix is used as the basis for the deposition of silver and silver sulfide, and components such as silver and silver sulfide adhere to the three-dimensional matrix to form a spatial structure.

[0043] Optionally, the three-dimensional substrate may have a porous structure such as foam or sponge. The three-dimensional substrate may include at least one of materials such as melamine sponge, polydopamine sponge, nickel foam substrate, polyurethane sponge, lignin fiber, and nylon fiber. These materials have good durability, can withstand long-term use without easy wear and deformation, and have plasticity, meeting the requirements of wearable devices for materials. And these materials have good chemical stability, are not easily corroded and damaged by chemical substances, and can be used as three-dimensional substrates for various types of processing, meeting the preparation requirements of thermoelectric materials.

[0044] In a specific embodiment of the present application, step S100 may specifically include: soaking the substrate raw material in a sodium hydroxide solution with a concentration of 70-90 g / L for 30-60 minutes. Then washing the substrate raw material with deionized water and drying it to obtain a three-dimensional substrate.

[0045] In the method provided in this specific embodiment, treating the substrate raw material with a sodium hydroxide solution having a certain concentration can remove some impurities in the substrate raw material, such as dust and oil stains attached to the surface, so as to obtain a three-dimensional substrate with a surface suitable for silver deposition, making the combination of silver and the three-dimensional substrate more stable and facilitating the subsequent preparation process.

[0046] S200: Conduct a conductivity treatment on the surface of the three-dimensional substrate to obtain a conductive substrate.

[0047] For a three-dimensional substrate with poor conductivity or non-conductive, it is necessary to conduct a conductivity treatment on the surface of the three-dimensional substrate before electroplating so that it can be used as a cathode in electroplating.

[0048] The methods of conductivity treatment may include at least one of heating evaporation plating, ion plating, sputtering plating, electroless plating, coating conductive glue, coating conductive resin, and coating metal powder.

[0049] In a specific embodiment of the present application, in step S200, electroless plating may be specifically used to conduct a conductivity treatment on the surface of the three-dimensional substrate, and the process may specifically include:

[0050] S201: Prepare a reducing agent solution and prepare a silver ammonia solution.

[0051] Due to the perishable nature of the silver ammonia solution, the silver ammonia solution needs to be prepared temporarily during electroless silver plating.

[0052] In a specific embodiment of the present application, the step of preparing the reducing agent solution may include dissolving the main reducing agent, auxiliary reducing agent, dispersant, and cosolvent in deionized water to obtain a reducing agent solution.

[0053] Among them, the main reducing agent and the auxiliary reducing agent are used to reduce the silver ions in the silver ammonia solution, the dispersant is used to disperse the silver element reduced by the silver ions, and the co-solvent is used to dissolve the dispersant.

[0054] In the method provided in this specific embodiment, the main reducing agent and the auxiliary reducing agent cooperate with each other to reduce the silver element in the silver ammonia solution to silver element. The dispersant can play a stabilizing and dispersing role, preventing the reduced silver element from agglomerating, and making the generated silver mirror more uniform. Since the dispersant itself has a certain viscosity, in order to help the reaction system mix, adding a co-solvent can help the dispersant dissolve, so that it can be uniformly and stably present in the reaction system to play a role.

[0055] In a specific embodiment of the present application, the main reducing agent may include glucose monohydrate and glucose, the auxiliary reducing agent may include sodium potassium tartrate tetrahydrate and sodium potassium tartrate, the surfactant may include polyethylene glycol, and the cosolvent may include ethanol. Wherein, the mass ratio of glucose monohydrate, sodium potassium tartrate tetrahydrate, polyethylene glycol and ethanol is (35-45): (10-20): (0.1-1): (100-150). By adjusting the mass ratio of each component in the reaction system, the utilization rate of silver and various reagents can be effectively improved, which can reduce the cost while ensuring the reaction effect.

[0056] In the method provided in this specific embodiment, glucose has an aldehyde group, can reduce silver ions under alkaline conditions, and compared with other common reducing agents, its reduction process and reaction conditions are relatively mild, and the reaction rate is moderate, can provide guarantee for the quality of the plated surface, and safety is also higher. Sodium potassium tartrate can be used as an auxiliary reducing agent under alkaline conditions to enhance the reducing ability of the reaction, and can form a complex with silver ions to promote the reduction of silver ions, and can also be used to adjust the pH value of the system, providing guarantee for the alkaline environment of the reaction. Polyethylene glycol can also adjust the viscosity of the reaction system while playing a stable and dispersed role, so as to achieve the effect of controlling the reaction rate and making the quality of the plated surface higher. The water solvent system of ethanol and silver ammonia solution can be mutually soluble in any proportion. Due to the principle of similar dissolving, adding ethanol can promote the dissolution of solid polyethylene glycol in the reaction system, and ethanol can also play the effect of a surfactant, reduce the surface tension of the system, and make the silver mirror more easily attached to the surface of the three-dimensional matrix.

[0057] Further, the step of preparing the silver ammonia solution may include mixing silver nitrate, sodium hydroxide, ammonia water, and deionized water to prepare the silver ammonia solution. Among them, the mass ratio of glucose monohydrate, potassium sodium tartrate tetrahydrate, polyethylene glycol, ethanol, silver nitrate, and sodium hydroxide is (35-45):(10-20):(0.1-1):(100-200):(40-60):(20-30). When preparing the silver ammonia solution, the volume ratio of ammonia water to deionized water may be 4:6. By adjusting the proportions of the components in the reaction system, the utilization rates of silver and various reagents can be effectively improved, achieving the effect of reducing costs while ensuring the reaction effect.

[0058] S202: Mix the reducing agent solution and the silver ammonia solution to obtain a first mixed solution.

[0059] In step S202, the volume ratio of the silver ammonia solution to the reducing agent solution may specifically be 1:1.

[0060] S203: Immerse the three-dimensional substrate completely in the first mixed solution to deposit silver on the surface of the three-dimensional substrate.

[0061] In a specific embodiment of the present application, the step of immersing the three-dimensional substrate completely in the first mixed solution may include: immersing the three-dimensional substrate in the first mixed solution and squeezing the three-dimensional substrate until the residual bubbles in the three-dimensional substrate are squeezed out. For a porous three-dimensional substrate, when performing electroless silver plating during soaking, squeezing the three-dimensional substrate can effectively discharge the gas therein, enabling the plating solution to uniformly contact the surface of the three-dimensional substrate, thereby making the silver plating effect more uniform.

[0062] Optionally, in the soaking and / or washing in step S100, a similar method may also be used to squeeze the three-dimensional substrate so that the sodium hydroxide solution and / or the matrix raw material are in full contact to remove impurities.

[0063] S300: Prepare an electroplating solution using silver nitrate, use a conductive substrate as the cathode and elemental silver as the anode, and immerse the elemental silver and the conductive substrate in the electroplating solution for electroplating to obtain a silver-plated substrate.

[0064] In a specific embodiment of the present application, the step of preparing the electroplating solution using silver nitrate may specifically include:

[0065] S301: Mix the silver nitrate solution and the potassium metabisulfite solution to obtain a second mixed solution.

[0066] The silver nitrate solution can react with the potassium metabisulfite solution to generate potassium nitrate and silver metabisulfite in the solution. The chemical reaction formula is as follows.

[0067] K2S2O5 + 2AgNO3 → 2KNO3 + Ag2S2O5↓ S302: Immediately add the second mixed solution to the sodium thiosulfate solution to obtain a third mixed solution.

[0068] After immediately mixing the second mixture with the sodium thiosulfate solution after the formation of the second mixture, silver metabisulfite can react with sodium thiosulfate to form a relatively stable complex, so as to react with silver ions that are about to form silver metabisulfite precipitate to form a complex, thereby achieving the effect of stabilizing silver ions and preventing them from precipitating prematurely. The chemical reaction formula is as follows.

[0069] Ag2S2O5 + Na2S2O3 → complex

[0070] S303: Add a pH buffer and a brightener to the third mixture to obtain an electroplating solution.

[0071] To maintain a stable silver complex, the pH value of the electroplating solution is preferably maintained in weakly acidic. Therefore, the acidity of the electroplating solution can be maintained by adding a pH buffer, and the brightener can be used to improve the surface performance of the plating surface to pursue better thermoelectric performance.

[0072] In a specific embodiment of the present application, the pH buffer may include ammonium acetate, and the brightener may include thiosemicarbazide. Among them, the mass ratio of silver nitrate in the silver nitrate solution, potassium metabisulfite in the potassium metabisulfite solution, sodium thiosulfate in the sodium thiosulfate solution, ammonium acetate, and thiosemicarbazide is (40 - 50):(20 - 30):(200 - 250):(20 - 30):(0.1 - 1).

[0073] Through the method provided by this specific embodiment, the sulfur atom and nitrogen atom with lone pair electrons in thiosemicarbazide can be used to form a stable coordination compound with silver ions (Ag + )), such as Ag(H2NCSNH2)3 + . This coordination effect can enhance the stability of the plating solution, prevent silver ions from precipitating prematurely, thereby improving the surface performance of the plating surface. And thiosemicarbazide can be adsorbed on the metal surface, changing the electronic structure of the metal surface, thereby controlling the deposition rate of silver ions, making the coating more uniform and delicate, and improving the flatness and brightness of the coating. Thiosemicarbazide can also be used as a chemical stabilizer to adjust the reaction rate of the plating solution, prevent the plating solution from decomposing or overreacting, and thus extend the service life of the plating solution.

[0074] Ammonium acetate can adjust the acidity and alkalinity of the electroplating solution, provide a certain buffering capacity, and keep the pH value of the electroplating solution relatively stable. This is crucial for maintaining the balance of various chemical reactions in the electroplating solution. Ammonium acetate can increase the ion concentration of the plating solution, thereby improving the conductivity of the plating solution and making the electroplating process more efficient. Ammonium acetate can form a complex with silver ions, further stabilizing the metal ions in the plating solution, and also helping to improve the adhesion and corrosion resistance of the coating.

[0075] Thiosemicarbazide and ammonium acetate act synergistically to maintain the stability of the electroplating solution while refining the coating, which can well ensure the quality of the coating.

[0076] In a specific embodiment of the present application, the step of immersing elemental silver and a conductive substrate in the electroplating solution for electroplating may specifically include: immersing elemental silver and a conductive substrate in the electroplating solution, and electroplating for 1 to 4 hours under the conditions of a current of 0.018 to 0.04 A, a stirring rotor speed of 300 to 500 rpm, and a temperature of 25 to 35 °C. By controlling the electroplating temperature, stirring speed, and electroplating current, a silver selenide three-dimensional structure thermoelectric material with a good surface morphology, excellent thermoelectric properties, and certain elasticity and flexibility can be obtained.

[0077] S400: Prepare a selenium solution, add the silver-plated substrate to the selenium solution and soak it to obtain a silver selenide three-dimensional structure thermoelectric material.

[0078] In a specific embodiment of the present application, the step of preparing the selenium solution may specifically include: dissolving sodium sulfide nonahydrate in deionized water, and then adding selenium to obtain a selenium solution. Among them, the mass ratio of sodium sulfide nonahydrate to selenium may specifically be (2.5 to 3.5):(0.5 to 1.5).

[0079] In this specific embodiment, controlling the mass ratio of sodium sulfide nonahydrate to selenium within the range of (2.5 to 3.5):(0.5 to 1.5) can effectively control the composition of the product obtained in step S400, so that the product is mainly silver selenide, rather than silver thioselenide or silver sulfide.

[0080] In the method provided in this specific embodiment, the three-dimensional substrate is first conductivized to enable it to conduct current. On this basis, with the conductive substrate as the cathode and elemental silver as the anode, silver is plated on the surface of the conductive substrate by an electrochemical method in the electroplating solution. Compared with the common electroless plating method, a larger silver loading can be applied in a single silver plating process. The electrochemical silver plating method has a higher plating speed, and the utilization rate of silver as the plating raw material is also higher, which can effectively increase the loading of silver selenide in the three-dimensional structure thermoelectric material, and thus achieve the effect of improving the thermoelectric properties of the silver selenide three-dimensional structure thermoelectric material.

[0081] The following provides multiple embodiments of the present application.

[0082] Example 1

[0083] Step 1: Immerse a melamine sponge (Basotect; BASF) in an 80 g / L NaOH solution for 30 minutes, then wash it with deionized water, and then dry it to obtain.

[0084] Step 2: Add 40 g of glucose monohydrate (C6H 12O6·H2O, AR; Hushi), 14 g of potassium sodium tartrate tetrahydrate (C4H4O6KNa·4H2O, AR, 99%; Aladdin), 0.1 g of polyethylene glycol (PEG1000, CP; Hushi), and 100 g of ethanol were dissolved in 1 L of deionized water to prepare a reducing agent solution. 50 g of silver nitrate (AgNO3, 98%; TBHX), 25 g of sodium hydroxide (NaOH, AR; Xilong Scientific), 400 mL of ammonia water (AR; Macklin), and 600 mL of deionized water were mixed to prepare a silver ammonia solution. The reducing agent solution and the silver ammonia solution were mixed to obtain a first mixed solution, and then the three-dimensional substrate was immersed in the first mixed solution and gently squeezed to extrude the residual bubbles in the three-dimensional substrate.

[0085] Step 3: 45 g of AgNO3 and 25 g of potassium metabisulfite (K2S2O5) were respectively dissolved in 250 mL of deionized water to prepare a silver nitrate solution and a potassium metabisulfite solution. 225 g of sodium thiosulfate was dissolved in deionized water to prepare a sodium thiosulfate solution with a volume less than 500 mL. Under stirring conditions, the potassium metabisulfite solution was poured into the silver nitrate solution to generate a second mixed solution (silver metabisulfite turbid solution). Then, the second mixed solution was immediately and slowly added to the sodium thiosulfate solution to coordinate silver element with sodium thiosulfate to generate a slightly yellowish third mixed solution. Then, 25 g of ammonium acetate was added to the third mixed solution, and after standing for a period of time, 0.6 g of thiosemicarbazide was added and dissolved completely. Finally, deionized water was added to the electroplating solution to make its volume reach 1 L. The above-mentioned silver-plated foam was hooked with a wire and immersed in the electroplating solution as the cathode. A silver plate was clamped with an alligator clip as the anode, and electroplating was carried out with a DC regulated power supply. The current was set to 0.018 A, the rotor speed was set to 400 rpm, the temperature was set to 30 °C, and the electroplating duration was 2 hours. After electroplating, it was washed with pure water and dried for standby.

[0086] Step 4: 60 g of sodium sulfide nonahydrate (Na2S·9H2O, 98%; Aladdin) and 20 g of selenium powder (Se, 99.9%; Innochem) were dissolved in 1 L of deionized water to prepare a selenium solution. Then, the above-mentioned silver network was immersed in the selenium solution for 10 h to synthesize a silver selenide three-dimensional structure thermoelectric material.

[0087] Step 5: Wash the silver selenide three-dimensional structure thermoelectric material with deionized water.

[0088] Example 2

[0089] Compared with Example 1, other conditions remained unchanged, and the electroplating current was set to 0.025 A.

[0090] Example 3

[0091] Other conditions remained unchanged compared with Example 1, and the electroplating current was set to 0.032 A.

[0092] Example 4

[0093] Other conditions remained unchanged compared with Example 1, and the electroplating current was set to 0.040 A.

[0094] Example 5

[0095] Other conditions remained unchanged compared with Example 2, and the electroplating duration was set to 1 hour.

[0096] Example 6

[0097] Other conditions remained unchanged compared with Example 2, and the electroplating duration was set to 3 hours.

[0098] Example 7

[0099] Other conditions remained unchanged compared with Example 2, and the electroplating duration was set to 4 hours.

[0100] Figure 1 It is the conductivity statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 2 It is the Seebeck coefficient statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 3 It is the power factor statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 4 It is the thermal conductivity statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 5 It is the thermoelectric figure of merit statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application.

[0101] Table 1 is the statistical table of the thermoelectric performance values of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application.

[0102] Table 1

[0103]

[0104] Refer to Figure 15 , Figure 15 It is the phase statistical chart of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application.

[0105] Table 2 is a statistical table of the phase data of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material.

[0106] Table 2

[0107] Electroplating duration Silver loading Silver selenide loading Density Porosity 1h 0.259545455 0.318181818 0.016632231 94.55 2h 0.45 0.575 0.017215909 91.05 3h 0.664090909 0.888636364 0.017928719 87.3 4h 0.834545455 1.136363636 0.018491736 84.05

[0108] Refer to Figures 1 to 5 、 Figure 15 、Table 1 and Table 2. It is not difficult to find that due to the positive correlation between the electroplating duration and the silver loading, silver selenide loading, and density, and the negative correlation between the electroplating duration and the porosity. When the electroplating current remains unchanged, the conductivity, power factor, thermal conductivity, and thermoelectric figure of merit of the silver selenide three-dimensional structure thermoelectric material at various temperatures all increase with the increase in the silver and silver selenide loadings, which can reflect the positive impact of the silver selenide loading on the thermoelectric performance of the silver selenide three-dimensional structure thermoelectric material.

[0109] Refer to Figure 6 , Figure 6 is a statistical chart of the mechanical and electrical properties of the fifth, second, sixth, and seventh embodiments of the silver selenide three-dimensional structure thermoelectric material of the present application.

[0110] Figure 6 In the upper left corner is the stress-strain statistical chart of the fifth, second, sixth, and seventh embodiments. It can be found that there is a positive correlation between the silver selenide loading and the elastic moduli E1, E2, E3, and E4. Figure 6 The stress-strain curves with different compression amounts are in the upper left corner. It can be found that the silver selenide three-dimensional structure thermoelectric material of the present application can exhibit good elasticity at compression amounts of 5%, 10%, 15%, and 20%, meeting the requirements of wearable thermoelectric devices.

[0111] Therefore, considering the flexibility, elasticity, and thermoelectric performance of the silver selenide three-dimensional structure thermoelectric material, the preferred electroplating time is 2 hours.

[0112] Figure 6 The resistivity-cycle number graphs of the silver selenide three-dimensional structure thermoelectric material at different load ratios ε c are respectively in the lower left corner and the lower right corner. It can be found that under the conditions of different load ratios ε c , the resistivity of the silver selenide three-dimensional structure thermoelectric material does not increase significantly with the increase in the cycle number, and it has good cycle performance.

[0113] Refer to Figures 10 to 14 , Figure 11 is the electron microscope image of the fifth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 12 is the electron microscope image of another position of the second embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 13It is an electron micrograph of the sixth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 14 It is an electron micrograph of the seventh embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. It is not difficult to find that when the electroplating current remains unchanged, the thickness of the coating shows a positive correlation with the electroplating time, which is in line with the fact that the longer the electroplating time, the higher the loading of silver and silver selenide.

[0114] Refer to Figures 7 to 10 , Figure 7 It is an electron micrograph of the first embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 8 It is an electron micrograph of the second embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 9 It is an electron micrograph of the third embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. Figure 10 It is an electron micrograph of the fourth embodiment of the silver selenide three-dimensional structure thermoelectric material of the present application. It is not difficult to find that when the electroplating time remains unchanged and the electroplating currents are 0.018 A and 0.025 A, the silver selenide three-dimensional structure thermoelectric material has a good surface morphology, indicating that the electroplating process proceeds slowly and evenly. When the electroplating current reaches 0.032 A or even 0.04 A, the surface of the silver selenide three-dimensional structure thermoelectric material begins to become significantly rough, indicating that too fast electroplating process is not conducive to forming good surface properties. Therefore, considering the electroplating time and surface morphology comprehensively, the preferred electroplating current is 0.025 A.

[0115] The above are only the specific implementation manners of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and retouches can still be made, and these improvements and retouches should also be regarded as the protection scope of the present application.

Claims

1. A method for preparing a three-dimensional structured silver selenide thermoelectric material, characterized in that: include: providing a three-dimensional matrix; Conducting a conductive treatment on the surface of the three-dimensional matrix to obtain a conductive matrix; Prepare an electroplating solution using silver nitrate, use the conductive substrate as a cathode and elemental silver as an anode, immerse the elemental silver and the conductive substrate in the electroplating solution for electroplating, and obtain a silver-plated substrate; A selenium solution is prepared, and the silver-plated substrate is added into the selenium solution and immersed to obtain a silver selenide three-dimensional structure thermoelectric material.

2. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 1, characterized in that: The conducting treatment on the surface of the three-dimensional substrate comprises: Prepare a reducing agent solution and a silver ammonia solution; Mixing the reducing agent solution with the silver ammonia solution to obtain a first mixed solution; The three-dimensional matrix is ​​completely immersed in the first mixed liquid, and silver is plated on the surface of the three-dimensional matrix.

3. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 2, characterized in that: The reducing agent solution is prepared as follows: Dissolving a main reducing agent, an auxiliary reducing agent, a dispersant and a co-solvent in deionized water to obtain the reducing agent solution; The main reducing agent and the auxiliary reducing agent are used to reduce the silver ions in the silver ammonia solution, the dispersant is used to disperse the silver element reduced by the silver ions, and the co-solvent is used to dissolve the dispersant.

4. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 3, characterized in that: The main reducing agent includes glucose monohydrate, the auxiliary reducing agent includes potassium sodium tartrate tetrahydrate, the surfactant includes polyethylene glycol, and the cosolvent includes ethanol; Wherein, the mass ratio of the glucose monohydrate, the potassium sodium tartrate tetrahydrate, the polyethylene glycol and the ethanol is (35-45):(10-20):(0.1-1):(100-150).

5. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 2, characterized in that: The step of completely immersing the three-dimensional matrix in the first mixed liquid comprises: The three-dimensional matrix is ​​immersed in the first mixed liquid, and the three-dimensional matrix is ​​squeezed until the bubbles remaining in the three-dimensional matrix are squeezed out.

6. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 1, characterized in that: The preparation of the electroplating solution using silver nitrate comprises: mixing the silver nitrate solution with the potassium pyrosulfite solution to obtain a second mixed solution; Immediately adding the second mixed solution to the sodium thiosulfate solution to obtain a third mixed solution; A pH buffer and a brightener are added to the third mixed solution to obtain the electroplating solution.

7. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 6, characterized in that: The pH buffer comprises ammonium acetate, and the brightener comprises thiosemicarbazide; Among them, the mass ratio of silver nitrate in the silver nitrate solution, potassium pyrosulfite in the potassium pyrosulfite solution, sodium thiosulfate in the sodium thiosulfate solution, the ammonium acetate, and the thiosemicarbazide is (40-50):(20-30):(200-250):(20-30):(0.1-1).

8. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 1, characterized in that: The step of immersing the elemental silver and the conductive substrate in the electroplating solution for electroplating comprises: The elemental silver and the conductive substrate are immersed in the electroplating solution, and electroplated for 1 to 4 hours under the conditions of a current of 0.018 to 0.04 A, a stirring rotor speed of 300 to 500 rpm, and a temperature of 25 to 35° C.

9. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 1, characterized in that: The selenium solution is prepared as follows: Dissolving sodium sulfide nonahydrate in deionized water, and then adding selenium to obtain the selenium solution; Wherein, the mass ratio of the sodium sulfide nonahydrate to the selenium is (2.5-3.5):(0.5-1.5).

10. The method for preparing the silver selenide three-dimensional structure thermoelectric material according to claim 1, characterized in that: Providing a three-dimensional matrix comprises: Soaking the matrix material in a sodium hydroxide solution with a concentration of 70 to 90 g / L for 30 to 60 minutes; Washing the matrix raw material with deionized water and drying it to obtain the three-dimensional matrix; Wherein, the three-dimensional matrix includes at least one of melamine sponge, polyurethane sponge, lignin fiber and nylon fiber.

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