Double-layer honeycomb n-type thermo-electric aerogel phase change composite material as well as preparation method and application thereof

Abstract

The invention discloses a double-layer honeycomb n-type thermo-electric aerogel phase change composite material and a preparation method and application thereof.The method comprises the steps that 1, an organic metal compound, an amine material and a carbon nano tube are taken and added into absolute ethyl alcohol, a mixed solution A is obtained, stirring and vacuum drying are conducted, and n-type doped CNT is obtained; 2, adding dialdehyde polysaccharide, collagen, n-type doped CNT and a silane coupling agent into deionized water, stirring to obtain an n-type doped CNT / collagen co-suspension, injecting the n-type doped CNT / collagen co-suspension into a mold, and performing one-way freezing to obtain n-type doped CNT / collagen ice gel; and 3, adding dialdehyde polysaccharide, collagen, n-type doped CNT, a silane coupling agent and polyethylene glycol into deionized water to obtain a mixed solution C, stirring to obtain an n-type doped CNT / collagen / PEG co-suspension, injecting the n-type doped CNT / collagen / PEG co-suspension into a mold filled with n-type doped CNT / collagen ice gel, and performing one-way freezing and vacuum freeze drying to obtain the double-layer honeycomb n-type thermo-electric gel phase change composite material. And efficient photo-thermal conversion, heat energy storage and thermoelectric power generation are realized.

Description

Technical Field

[0001] This invention relates to high-efficiency flexible thermoelectric materials, specifically a double-layer honeycomb n-type thermoelectric gel phase change composite material, its preparation method, and its application. Background Technology

[0002] As smart wearable devices gradually develop towards lower power consumption and portability, the demand for miniature flexible wearable generators to power them is increasing. Among various power generation modes, generating electricity using natural energy has the advantages of being environmentally friendly and clean. Among these, thermal energy, as an ubiquitous natural energy source, offers broad development prospects for wearable power generation devices. However, traditional wearable thermoelectric generators have low energy conversion efficiency and unstable heat sources.

[0003] Thermoelectric materials can be classified into p-type and n-type based on their primary charge carrier type. The primary charge carrier in p-type thermoelectric materials is the hole, with an S value greater than 0; the primary charge carrier in n-type thermoelectric materials is the electron, with an S value less than 0. A complete thermoelectric device requires both n-type and p-type thermoelectric materials to operate simultaneously. However, the development of existing n-type thermoelectric materials lags behind that of p-type thermoelectric materials, resulting in slow progress in the research of n-type semiconductors. Although the mobility of existing n-type semiconductors is acceptable, their intrinsic carrier concentration is mostly low, and their electron affinity is low, meaning their lowest occupied molecular orbital (LUMO) energy level is high, leading to poor stability and difficulty in meeting the requirements of thermoelectric conversion. Therefore, it is urgent to strengthen the development of high-performance n-type thermoelectric materials.

[0004] Flexible thermoelectric power generation devices are assembled by laying out organic thermoelectric thin films. Two-dimensional thermoelectric generators with parallel structures can only collect heat energy in a planar direction and cannot match the vertical temperature gradient between the heat source and the environment. They are usually not able to effectively convert heat energy. In contrast, vertical thermoelectric devices can significantly increase the temperature difference between the hot and cold sides through thicker three-dimensional thermoelectric legs, effectively utilizing the temperature gradient between the heat source and the environment to generate high output voltage and power. In nature, wood has an ordered layered porous structure and exhibits obvious anisotropy in the directional transport of water and nutrients. The unique ordered structure provides wood with a certain load-bearing function, and the hollow tubular structure of wood can serve as a substrate for loading functional materials, providing a good platform for developing three-dimensional functional composite materials with significant thermoelectric properties.

[0005] In addition, phase change materials (PCMs) are materials that absorb or release heat energy during phase change, thereby playing the role of energy storage and temperature regulation. They are widely used in fields such as smart fabrics, energy-saving buildings, commercial refrigeration and waste heat recovery. They have the advantages of high energy storage density and near isothermal phase change process, which can store sufficient heat and achieve stable heat source output, enabling thermoelectric generators to obtain stable and long-lasting output voltage.

[0006] In summary, it is hoped that by preparing n-type thermoelectric gel phase change materials with a wood-like structure, the conductive materials can be arranged in an orderly manner, increasing the carrier migration rate and thus improving the thermoelectric properties of the aerogel and endowing it with excellent mechanical properties. On the other hand, the phase change material can play a role in energy storage and temperature regulation. Applying this n-type thermoelectric gel phase change material to wearable thermoelectric power generation devices and combining it with solar thermal conversion technology can help collect outdoor heat energy, thereby solving the problem of insufficient heat energy sources. This will achieve a more optimized allocation of natural energy and meet the heat energy needs of portable thermoelectric power generation devices. This has significant value and importance for the sustainable use of energy and the stable and healthy development of the future flexible wearable field. Summary of the Invention

[0007] The purpose of this invention is to provide a double-layer honeycomb n-type thermoelectric gel phase change composite material, its preparation method and application, which realizes efficient photothermal conversion, thermal energy storage and thermoelectric power generation.

[0008] This invention is achieved through the following technical solution: A method for preparing a double-layer honeycomb n-type thermo-electric gel phase change composite material includes the following steps: Step 1: Take organometallic compounds, amine materials, and carbon nanotubes according to a mass ratio of (1~10):(1~10):(50~100), and add them to anhydrous ethanol to obtain mixed solution A. Stir at 30~50℃ for 12~24 h, and then vacuum dry to obtain n-type doped CNTs. The mass fraction of anhydrous ethanol in mixed solution A is 60%~80%. The organometallic compound is ferrocene or a ferrocene derivative, and the ferrocene derivative is diethylene glycol-modified ferrocene, ferrocene acetylene, or N,N'-dimethylferrocene methylamine. The amine material is polyethyleneimine, oleylamine, diethylenetriamine, or triethylamine; Step 2: Take dialdehyde polysaccharide, collagen, n-type doped CNTs and silane coupling agent according to the mass ratio (1~5):(50~100):(1~50):(1~5) and add them to deionized water to obtain mixed solution B. Stir at 10~50℃ for 6~18 h to obtain an n-type doped CNT / collagen co-suspension. Then inject it into a mold and freeze it unidirectionally to obtain an n-type doped CNT / collagen ice gel. The mass fraction of deionized water in the mixed solution B is 70%~90%. Step 3: Take dialdehyde polysaccharide, collagen, n-type doped CNT, silane coupling agent and polyethylene glycol according to the mass ratio (1~5):(50~100):(1~50):(1~5):(20~80) and add them to deionized water to obtain mixed solution C. Stir at 10~50℃ for 6~18 h to obtain n-type doped CNT / collagen / PEG co-suspension. Then inject it into a mold containing n-type doped CNT / collagen ice gel, and freeze-dry it in a unidirectional manner and under vacuum to obtain a double-layer honeycomb n-type thermo-electrogel phase change composite material. The mass fraction of deionized water in the mixed solution C is 70%~90%.

[0009] Furthermore, the carbon nanotubes in step 1 are basic carbon nanotubes, aminated single-walled carbon nanotubes, or carboxylated single-walled carbon nanotubes with a diameter of 1~15 nm and a length of 1~60 μm.

[0010] Furthermore, the vacuum drying in step 1 is carried out at 60~100℃ for 24~72 h.

[0011] Furthermore, the dialdehyde polysaccharide in steps 2 and 3 is dialdehyde chitosan, dialdehyde carboxymethyl cellulose, or dialdehyde starch.

[0012] Further, the silane coupling agent in steps 2 and 3 is γ-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0013] Furthermore, the unidirectional freezing in steps 2 and 3 is performed at -30 to -80°C for 0.5 to 2 hours.

[0014] Furthermore, the molecular weight of the polyethylene glycol in step 3 is 2000~10000.

[0015] Furthermore, the vacuum freeze-drying in step 3 is carried out using a vacuum freeze dryer at a pressure of 1~10 Pa and a temperature of -70~-50℃ for 24~72 h.

[0016] A double-layered honeycomb n-type thermo-electric gel phase change composite material.

[0017] Application of a double-layer honeycomb n-type thermoelectric gel phase change composite material as a thermoelectric generator.

[0018] The present invention has the following beneficial technical effects: 1) This invention uses amine materials, carbon nanotubes with excellent photothermal conversion performance, ferrocene and its derivatives rich in electron-donating groups, and environmentally friendly and widely available collagen as raw materials, and dialdehyde polysaccharides and silane coupling agents as crosslinking agents to prepare a double-layer honeycomb n-type thermo-electric gel phase change composite material. This composite material possesses the advantages of being ultralight, flexible, having a large specific surface area and high porosity, as well as good compression resilience and mechanical compressive strength. Specifically, firstly, ferrocene and its derivatives and amine materials, without affecting the excellent photothermal conversion performance of carbon nanotubes, First, the synthesis of a bilayer honeycomb n-type thermoelectric gel phase change composite material provides a large number of electrons to achieve n-type doping, which synergistically enhances air stability and improves thermoelectric performance by utilizing energy filtering effect. Second, the bilayer honeycomb microstructure of the synthesized bilayer honeycomb composite material, with its high porosity and large specific surface area, provides a fast channel for charge carrier conduction, thereby achieving efficient thermoelectric conversion performance and significantly improving the mechanical properties of the material. Third, the phase change material PEG can store sufficient heat and achieve stable heat source output, thereby generating continuous and stable electrical energy and achieving power output without a heat source.

[0019] 2) This invention uses directional cryogenic casting technology to create a directional temperature gradient in the solution. By using ice crystals to arrange and compress collagen, a directional ordered porous structure is formed, thus preparing an n-type thermoelectric gel phase change composite material with a honeycomb structure. This provides a fast channel for the directional conduction of charge carriers, achieving efficient thermoelectric conversion performance and significantly improving the mechanical properties of the material, resulting in excellent compressive resilience.

[0020] 3) The n-type thermoelectric gel phase change composite material prepared by this invention has a double-layer structure, wherein: the upper layer is a honeycomb-structured n-type doped CNT / collagen ice gel composite PEG high-efficiency photothermal conversion and thermal energy storage layer with excellent photothermal conversion performance, thermal energy storage and good thermoelectric conversion performance; the lower layer is a honeycomb-structured n-type doped CNT / collagen aerogel high-efficiency thermoelectric conversion layer with excellent thermoelectric conversion performance; when there is a solar light source, the upper layer converts solar energy into thermal energy, creating a temperature gradient inside the double-layer honeycomb n-type thermoelectric gel phase change composite material, and then realizing thermoelectric conversion by utilizing the Seebeck effect. At the same time, the upper layer can also store part of the thermal energy converted from solar energy. When there is no solar light source, it constructs a temperature gradient for the double-layer honeycomb n-type thermoelectric gel phase change composite material, enabling it to complete thermoelectric conversion and extending the thermoelectric power generation time.

[0021] 4) In this invention, polyethylene glycol is added to the system in situ as a phase change material. The preparation process is simple and controllable, and the porous structure of the aerogel can be preserved, which improves the flexibility of the phase change composite material. At the same time, the interaction between n-type doped CNTs, collagen and PEG can be used to prevent the phase change material from melting and leaking, which effectively improves the shape stability of the phase change composite material. It has good application prospects in wearable energy harvesting and smart sensing fields. Attached Figure Description

[0022] Figure 1 SEM images of the longitudinal and transverse sections and a photograph of the double-layer honeycomb n-type thermo-electric gel phase change composite material prepared in Example 2 of the present invention. Figure 2 The thermal conductivity of the double-layer honeycomb n-type thermo-electric gel phase change composite material prepared in Examples 2, 3 and 5 of this invention; Figure 3 The compression cycle curve of the double-layer honeycomb n-type thermo-electric gel phase change composite material prepared in Example 2 of the present invention is shown. Figure 4 The present invention relates to a solar thermoelectric generator photothermal performance testing device and test results. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0024] The diethylene glycol-modified ferrocene used in Examples 2 and 3 of this invention is referenced in [Enhanced Thermoelectric Properties of Stable n-Type Ferrocene Derivatives-Doped Polyethylenimine / Single-Walled Carbon Nanotube Composite Films]. ACS Appl. Mater. Interfaces Prepared by [2024, 16, 54038-54048, DOI: 10.1021 / acsami.4c13344].

[0025] Example 1 Step 1: Weigh 10 g of N,N'-dimethylferroceneamine, 1 g of diethylenetriamine and 100 g of basic carbon nanotubes (CNTs) according to a mass ratio of 10:1:100, add them to 158.5 g of anhydrous ethanol, mechanically stir at 40°C for 12 h, and vacuum dry at 60°C for 72 h to obtain n-type doped CNTs; Step 2: Weigh 2.5 g of dialdehyde carboxymethyl cellulose, 50 g of collagen, 1 g of n-type doped CNT and 0.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane according to a mass ratio of 5:100:2:1, add them to 486 g of deionized water, stir at 50°C for 6 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 1 / 2 of the height inside the mold, and freeze unidirectionally at -30°C for 2 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh 2.5 g of dialdehyde carboxymethyl cellulose, 25 g of collagen, 0.5 g of n-type doped CNTs, 0.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 40 g of polyethylene glycol (PEG 2000) with a molecular weight of 2000 according to a mass ratio of 5:50:1:1:80. Add them to 616.5 g of deionized water and stir at 40°C for 6 h to obtain an n-type doped CNT / collagen / PEG co-suspension. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -30°C for 2 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 10 Pa and a temperature of -70°C for 48 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0026] Example 2 Step 1: Weigh 1 g of diethylene glycol-modified ferrocene, 10 g of polyethyleneimine (PEI), and 100 g of aminated single-walled carbon nanotubes according to a mass ratio of 1:10:100, add them to 444 g of anhydrous ethanol, mechanically stir at 30°C for 24 h, and vacuum dry at 100°C for 24 h to obtain n-type doped CNTs; Step 2: Weigh 0.5 g of dialdehyde carboxymethyl cellulose, 50 g of collagen, 25 g n-type doped CNTs and 0.5 g of γ-glycidyl etheroxypropyltrimethoxysilane according to a mass ratio of 1:100:50:1, add them to 684 g of deionized water, stir at 30 °C for 15 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 1 / 2 of the height inside the mold, and freeze unidirectionally at -80 °C for 0.5 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh out 0.5 g of dialdehyde carboxymethyl cellulose, 50 g of collagen, 25 gn-type doped CNTs, 0.5 g of γ-glycidyl etheroxypropyltrimethoxysilane, and 20 g of polyethylene glycol (PEG 8000) with a molecular weight of 8000 according to a mass ratio of 1:100:50:1:40. Add them to 684 g of deionized water and stir at 30°C for 15 h to obtain a co-suspension of n-type doped CNT / collagen / PEG. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -80°C for 1 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 1 Pa and a temperature of -70°C for 48 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0027] Example 3 Step 1: Weigh 10 g of diethylene glycol-modified ferrocene, 10 g of polyethyleneimine (PEI), and 100 g of carboxylated single-walled carbon nanotubes according to a mass ratio of 10:10:100. Add them to 280 g of anhydrous ethanol, mechanically stir at 50°C for 12 h, and vacuum dry at 80°C for 24 h to obtain n-type doped CNTs. Step 2: Weigh 0.5 g of dialdehyde starch, 25 g of collagen, 15 g n-type doped CNTs and 0.5 g of γ-glycidyl etheroxypropyltrimethoxysilane according to a mass ratio of 1:50:30:1, add them to 164 g of deionized water, stir at 30°C for 15 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 1 / 3 of the height inside the mold, and freeze unidirectionally at -80°C for 0.5 h to obtain an n-type doped CNT / collagen ice gel. Step 3: Weigh out 0.5 g of dialdehyde starch, 50 g of collagen, 15 gn-type doped CNTs, 0.5 g of γ-glycidyl etheroxypropyltrimethoxysilane, and 10 g of polyethylene glycol (PEG 10000) with a molecular weight of 10000 according to a mass ratio of 1:100:30:1:20. Add them to 264 g of deionized water and stir at 30°C for 15 h to obtain a co-suspension of n-type doped CNT / collagen / PEG. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -80°C for 1 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 1 Pa and a temperature of -70°C for 24 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0028] Example 4 Step 1: Weigh 5 g of N,N'-dimethylferrocene, 5 g of polyethyleneimine (PEI), and 100 g of aminated single-walled carbon nanotubes according to a mass ratio of 5:5:100. Add them to 165 g of anhydrous ethanol, mechanically stir at 40°C for 12 h, and vacuum dry at 60°C for 72 h to obtain n-type doped CNTs. Step 2: Weigh 2.5 g of dialdehyde carboxymethyl cellulose, 50 g of collagen, 0.5 g of n-type doped CNTs and 0.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane according to a mass ratio of 5:100:1:1, add them to 125 g of deionized water, stir at 40°C for 6 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 1 / 2 of the height inside the mold, and freeze unidirectionally at -30°C for 2 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh 2.5 g of dialdehyde carboxymethyl cellulose, 50 g of collagen, 0.5 g of n-type doped CNTs, 2.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 40 g of polyethylene glycol (PEG 2000) with a molecular weight of 2000 according to a mass ratio of 5:100:1:5:80. Add them to 223 g of deionized water and stir at 50°C for 6 h to obtain an n-type doped CNT / collagen / PEG co-suspension. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -30°C for 2 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 8 Pa and a temperature of -70°C for 48 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0029] Example 5 Step 1: Weigh 1 g of ferrocene acetylene, 10 g of triethylamine and 50 g of basic carbon nanotubes (CNTs) according to a mass ratio of 1:10:50, add them to 142 g of anhydrous ethanol, mechanically stir at 50°C for 24 h, and vacuum dry at 80°C for 48 h to obtain n-type doped CNTs. Step 2: Weigh 1.5 g of dialdehyde chitosan, 50 g of collagen, 25 g of n-type doped CNTs and 1.5 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane according to a mass ratio of 3:100:50:3, add them to 312 g of deionized water, stir at 30°C for 12 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 2 / 3 of the height inside the mold, and freeze unidirectionally at -80°C for 1 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh out 1.5 g of dialdehyde chitosan, 50 g of collagen, 25 g of n-type doped CNTs, 1.5 g of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 20 g of polyethylene glycol (PEG 6000) with a molecular weight of 6000 according to a mass ratio of 3:100:50:3:40. Add them to 312 g of deionized water and stir at 30°C for 12 h to obtain an n-type doped CNT / collagen / PEG co-suspension. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -80°C for 0.5 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 10 Pa and a temperature of -70°C for 72 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0030] Example 6 Step 1: Weigh 1 g of N,N'-dimethylferroceneamine, 5 g of oleylamine and 50 g of carboxylated single-walled carbon nanotubes according to a mass ratio of 1:5:50, add them to 84 g of anhydrous ethanol, mechanically stir at 40°C for 24 h, and vacuum dry at 100°C for 24 h to obtain n-type doped CNTs. Step 2: Weigh 2.5 g of dialdehyde starch, 25 g of collagen, 25 g of n-type doped CNTs and 2.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane according to a mass ratio of 5:50:50:5, add them to 128.5 g of deionized water, stir at 10°C for 18 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 2 / 3 of the height inside the mold, and freeze unidirectionally at -50°C for 0.5 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh out 0.5 g of dialdehyde starch, 25 g of collagen, 25 g of n-type doped CNTs, 2.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 30 g of polyethylene glycol (PEG 8000) with a molecular weight of 8000 according to a mass ratio of 1:50:50:5:60. Add them to 332 g of deionized water and stir at 10°C for 18 h to obtain an n-type doped CNT / collagen / PEG co-suspension. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -50°C for 2 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 5 Pa and a temperature of -50°C for 48 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0031] Example 7 Step 1: Weigh 6 g of ferrocene, 6 g of oleylamine and 75 g of carboxylated single-walled carbon nanotubes according to a mass ratio of 6:6:75, add them to 348 g of anhydrous ethanol, mechanically stir at 30°C for 18 h, and vacuum dry at 70°C for 36 h to obtain n-type doped CNTs. Step 2: Weigh 1.5 g of dialdehyde starch, 37.5 g of collagen, 12.5 g of n-type doped CNTs and 1.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane according to a mass ratio of 3:75:25:3, add them to 159 g of deionized water, stir at 20°C for 10 h to obtain an n-type doped CNT / collagen co-suspension, then inject it into a mold, with the liquid level of the co-suspension being 2 / 3 of the height inside the mold, and freeze unidirectionally at -60°C for 1.5 h to obtain an n-type doped CNT / collagen ice gel; Step 3: Weigh out 1.5 g of dialdehyde starch, 37.5 g of collagen, 12.5 g of n-type doped CNTs, 2.5 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 10 g of polyethylene glycol (PEG 8000) with a molecular weight of 8000 according to a mass ratio of 3:75:25:5:20. Add them to 170 g of deionized water and stir at 20°C for 10 h to obtain an n-type doped CNT / collagen / PEG co-suspension. Then, inject it into a mold containing n-type doped CNT / collagen ice gel, with the liquid level of the co-suspension level with the mold. Freeze unidirectionally at -60°C for 1.5 h, and then freeze-dry in a vacuum freeze dryer at a pressure of 6 Pa and a temperature of -60°C for 36 h to obtain a double-layer honeycomb n-type thermo-electric gel phase change composite material.

[0032] Figure 1 In Figures a and b, respectively, are SEM images of the axial and radial sections of the lower layer structure of the bilayer honeycomb n-type thermoelectric gel phase change composite material prepared in Example 2. It can be seen that the upper layer structure (i.e., n-type doped CNT / collagen ice gel) exhibits an ordered parallel sheet structure in the axial direction (i.e., parallel to the ice growth direction) and an interconnected porous structure in the radial direction (perpendicular to the ice growth direction). Figure 1 c and d are SEM images of the axial and radial sections of the upper structure of the double-layer honeycomb n-type thermo-electric gel phase change composite material prepared in Example 2, respectively. It can be seen that the upper structure exhibits an ordered parallel lamellar structure in the axial direction and an interconnected porous structure in the radial direction. Moreover, the porous structure of the upper structure is more compact and the skeleton structure is thicker than that of the lower structure. Figure 1The image in Figure 'e' shows a photograph of the double-layer honeycomb n-type thermo-electric gel phase change composite material prepared in Example 2. It can be seen that when the aerogel composite phase change material is placed on foxtail grass, it does not bend the fine hairs on the grass, indicating that it has lightweight properties.

[0033] Figure 2 The thermal conductivity of the bilayer honeycomb n-type thermo-electric gel phase change composite materials prepared in Examples 2, 3, and 5 is shown. It can be seen that the thermal conductivity of the bilayer honeycomb n-type thermo-electric gel phase change composite materials prepared in all three examples is less than 0.1 W / m. K has ultra-low thermal conductivity, which is beneficial for the construction of vertical temperature differences.

[0034] Figure 3 The compression cycle curve of the bilayer honeycomb n-type thermo-electric gel phase change composite material prepared in Example 2 shows that the aerogel phase change composite material still has good compression resilience at 50% strain.

[0035] Using the technical solutions of Examples 2, 3, and 5, nine identical double-layered honeycomb n-type thermoelectric gel phase change composite materials were prepared. These were then connected in series to form a thermoelectric generator, and their photothermal and electroelectric properties were tested. The testing apparatus is described below. Figure 4 a, Figure 4 b shows the effect at 150 mW / cm 2 The output voltage-time evolution curve under light intensity shows that the thermoelectric generator has excellent photothermal conversion performance, can quickly convert light energy into heat energy, and then use the Seebeck effect to convert heat energy into electrical energy. Moreover, it can still guarantee voltage output for a period of time after the light source is removed.

Claims

1. A method for preparing a double-layered honeycomb n-type thermo-electric gel phase change composite material, characterized in that, Includes the following steps: Step 1: Take organometallic compounds, amine materials, and carbon nanotubes according to a mass ratio of (1~10):(1~10):(50~100), and add them to anhydrous ethanol to obtain mixed solution A. Stir at 30~50℃ for 12~24 h, and then vacuum dry to obtain n-type doped CNTs. The mass fraction of anhydrous ethanol in mixed solution A is 60%~80%. The organometallic compound is ferrocene or a ferrocene derivative, and the ferrocene derivative is diethylene glycol-modified ferrocene, ferrocene acetylene, or N,N'-dimethylferrocene methylamine. The amine material is polyethyleneimine, oleylamine, diethylenetriamine, or triethylamine; Step 2: Take dialdehyde polysaccharide, collagen, n-type doped CNTs and silane coupling agent according to the mass ratio (1~5):(50~100):(1~50):(1~5) and add them to deionized water to obtain mixed solution B. Stir at 10~50℃ for 6~18 h to obtain an n-type doped CNT / collagen co-suspension. Then inject it into a mold and freeze it unidirectionally to obtain an n-type doped CNT / collagen ice gel. The mass fraction of deionized water in the mixed solution B is 70%~90%. Step 3: Take dialdehyde polysaccharide, collagen, n-type doped CNT, silane coupling agent and polyethylene glycol according to the mass ratio (1~5):(50~100):(1~50):(1~5):(20~80) and add them to deionized water to obtain mixed solution C. Stir at 10~50℃ for 6~18 h to obtain n-type doped CNT / collagen / PEG co-suspension. Then inject it into a mold containing n-type doped CNT / collagen ice gel, and freeze-dry it in a unidirectional manner and under vacuum to obtain a double-layer honeycomb n-type thermo-electrogel phase change composite material. The mass fraction of deionized water in the mixed solution C is 70%~90%.

2. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The carbon nanotubes in step 1 are basic carbon nanotubes, aminated single-walled carbon nanotubes, or carboxylated single-walled carbon nanotubes with a diameter of 1~15 nm and a length of 1~60 μm.

3. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The vacuum drying in step 1 is carried out at 60~100℃ for 24~72 h.

4. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The dialdehyde polysaccharide in steps 2 and 3 is dialdehyde chitosan, dialdehyde carboxymethyl cellulose, or dialdehyde starch.

5. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The silane coupling agent in steps 2 and 3 is γ-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

6. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The unidirectional freezing in steps 2 and 3 is performed at -30 to -80°C for 0.5 to 2 hours.

7. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The molecular weight of the polyethylene glycol in step 3 is 2000~10000.

8. The method for preparing the double-layer honeycomb n-type thermo-electric gel phase change composite material according to claim 1, characterized in that, The vacuum freeze-drying in step 3 is carried out using a vacuum freeze dryer at a pressure of 1~10 Pa and a temperature of -70~-50℃ for 24~72 h.

9. A method for preparing a bilayer honeycomb n-type thermo-electric gel phase change composite material according to any one of claims 1 to 8.

10. The application of the double-layer honeycomb n-type thermoelectric gel phase change composite material according to claim 8 as a thermoelectric generator.

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