Halloysite-reinforced polyurethane sponge: a solar interfacial evaporation material and its preparation method

Abstract

This invention discloses halloysite-reinforced polyurethane sponge solar interfacial evaporation material and its preparation method, comprising the following steps: Step 1, pretreating halloysite to obtain pretreated halloysite nanotubes; Step 2, pretreating polyurethane sponge to obtain activated polyurethane sponge; Step 3, preparing a mixed dispersion by reacting dopamine hydrochloride with the pretreated halloysite nanotubes, immersing the activated polyurethane sponge in the mixed dispersion and magnetically stirring to induce a self-polymerization reaction of dopamine hydrochloride, followed by rinsing and drying to obtain the halloysite-reinforced polyurethane sponge solar interfacial evaporation material. The material obtained by this invention exhibits good bonding between halloysite and polyurethane sponge.

Description

Technical Field

[0001] This invention belongs to the field of solar-driven interface evaporation material technology, specifically relating to a method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material, and also relating to halloysite-reinforced polyurethane sponge solar interface evaporation material. Background Technology

[0002] Solar-driven interfacial evaporation technology is a green technology that uses photothermal materials to convert solar energy into thermal energy and locally heat the water-air interface to produce freshwater. The core of this technology lies in developing evaporators with high-efficiency photothermal conversion, rapid water transport, good thermal management, and salt resistance. Polyurethane (PU) sponge, due to its three-dimensional porous structure, high porosity, excellent hydrophilicity, and low cost, is often used as the substrate material for evaporators. However, pure PU sponge has weak light absorption capacity, and its large-pore structure is not conducive to water transport, necessitating the loading of photothermal materials and hydrophilic / hydrophobic modification.

[0003] Halloysite nanotubes (HNTs) are a natural aluminosilicate clay mineral with a unique hollow tubular structure and abundant surface hydroxyl groups. They are inexpensive and biocompatible. Current research widely utilizes halloysite's natural hydrophilicity, hollow tubular structure, and the hierarchical channels formed when combined with other materials (such as PDA, graphene, and polymers) to enhance the overall capillary action and water transport capacity of composite materials, thereby solving the key bottleneck of insufficient water supply in interfacial evaporation. In existing technologies, halloysite is constructed through 3D printing and other techniques to create directional transport channels, or introduced during the preparation of hydrogels and aerogels (Zhao et al., Nano Res., 2025; Liu et al., Chem. Eng. J., 2025; Li et al., J. Clean. Prod., 2024; Chao et al., Journal of Henan Agricultural University, 2025). Utilizing halloysite's natural hydrophilicity, hollow tubular structure, and abundant surface hydroxyl groups, it is used as a functional unit in composites with various matrices. This allows for the formation of more micro- and nano-pores in a three-dimensional network, synergistically enhancing the material's hydrophilicity and water diffusion capacity. However, the bonding strength between halloysite nanotubes and the substrate is relatively poor in these methods. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material, thereby solving the problem that the materials obtained by existing methods have poor bonding strength between halloysite nanotubes and the substrate.

[0005] Another object of the present invention is to provide halloysite-reinforced polyurethane sponge solar interface evaporation material.

[0006] The technical solution adopted in this invention is a method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material, the steps of which are as follows:

[0007] Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; Step 3: Prepare a mixed dispersion by combining dopamine hydrochloride with pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and stir magnetically to induce a self-polymerization reaction of dopamine hydrochloride. After the reaction, rinse and dry to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material.

[0008] The invention is further characterized by: The specific process of step 1 is as follows: calcining halloysite nanotubes at 400℃~600℃ for 2h~4h, then ultrasonically treating them with hydrochloric acid at a concentration of 1mol / L~3mol / L for 20min~40min, followed by soaking for 1 day~3 days, then washing them with deionized water until neutral, and drying them to obtain pretreated halloysite nanotubes.

[0009] The specific process of step 2 is as follows: cut the polyurethane sponge into the required size, ultrasonically clean it with anhydrous ethanol to remove surface impurities, then soak it in NaOH solution. During soaking, squeeze the polyurethane sponge repeatedly to allow the NaOH solution to fully penetrate the pores of the sponge, then ultrasonically treat it, and then wash it repeatedly with deionized water until the washing solution is neutral. Take out the polyurethane sponge and dry it to obtain the activated polyurethane sponge.

[0010] The ultrasonic cleaning time is 20 min to 60 min, the concentration of NaOH solution is 1 mol / L to 3 mol / L, and the ultrasonic treatment time is 1 h to 2 h.

[0011] In step 3, the preparation process of the mixed dispersion is as follows: Dopamine hydrochloride is dissolved in Tris-HCl buffer solution with a pH of 8.0~9.0 to obtain a solution, and then pretreated halloysite nanotubes are added to the solution and ultrasonically dispersed to obtain a mixed dispersion.

[0012] The concentration of the solution was 5 mg / mL to 100 mg / mL; the mass ratio of dopamine hydrochloride to pretreated halloysite nanotubes was 1:0.02 to 10.

[0013] The ultrasonic dispersion time is 30 min to 60 min.

[0014] In step 3, the magnetic stirring temperature is 25℃~40℃, the magnetic stirring time is 12h~48h, and the drying temperature is 60℃~100℃.

[0015] Another technical solution adopted in this invention is a halloysite-reinforced polyurethane sponge solar interface evaporation material, which is prepared by the above-mentioned preparation method.

[0016] The beneficial effects of this invention are: (1) In the preparation method of the present invention, polydopamine can undergo self-polymerization on the surface of activated sponge skeleton and halloysite nanotubes under weak alkaline conditions to form a strong adhesion layer, which firmly loads halloysite nanotubes on the three-dimensional skeleton of polyurethane sponge, effectively preventing the halloysite nanotubes from falling off during use and improving the firmness of the bond between halloysite nanotubes and polyurethane sponge. (2) In the preparation method of the present invention, the microstructure and surface properties of halloysite nanotubes are optimized by calcination and acid treatment, which enhances capillary water absorption capacity and improves water transport performance. The introduction of polydopamine polymerizes on the surface of halloysite nanotubes to form a rough structure, which improves spectral absorption performance. The activated polyurethane sponge works synergistically with the capillary structure of halloysite nanotubes to achieve rapid water transport and localized evaporation. (3) The raw materials used in the preparation method of the present invention are inexpensive and readily available, the preparation process does not require complex equipment, the conditions are mild, and it is suitable for large-scale production. Attached Figure Description

[0017] Figure 1 These are images showing the surface area and pore volume of halloysite nanotubes after calcination treatment as used in Examples 1-3 and Comparative Example 1 of this invention. Figure 2 This is a SEM image of the PU sponge used in the method of this invention; Figure 3 This is a SEM image of the PU / PDA / HNT material obtained in Comparative Example 1 of this invention; Figure 4 This is a SEM image of the material obtained in Example 2 of the present invention; Figure 5 The photothermal conversion temperature-time curves of the materials obtained in Examples 1-3 and Comparative Examples 1-2 of this invention are shown. Figure 6 The evaporation rate diagrams are for the materials obtained in Examples 1-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] The preparation method of halloysite-reinforced polyurethane sponge solar interface evaporation material of the present invention comprises the following steps: Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; The specific process is as follows: Halloysite nanotubes were calcined at 400℃~600℃ for 2h~4h, cooled, and then ultrasonically treated with a hydrochloric acid solution of 1mol / L~3mol / L for 20min~40min. After soaking for 1 day~3 days, they were washed with deionized water until neutral and dried at 60℃~80℃ for 6h~12h to obtain pretreated halloysite nanotubes. The heating rate is 2℃ / min ~ 5℃ / min, and the calcination is carried out in an air atmosphere; The ratio of halloysite nanotubes to hydrochloric acid solution was 1 g: 50 mL. Within this calcination temperature range, bound water can be effectively removed and the crystal structure adjusted without destroying its tubular morphology. Hydrochloric acid treatment is used for further purification and to increase surface active sites; Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; The specific process is as follows: cut the polyurethane sponge into the required size (2cm×2cm×1cm), ultrasonically clean it with anhydrous ethanol for 20min~60min to remove surface impurities, take it out, squeeze it dry, and soak it in a NaOH solution with a concentration of 1mol / L~3mol / L. During soaking, squeeze the polyurethane sponge repeatedly to allow the NaOH solution to fully penetrate the sponge pores. Then ultrasonically treat it for 1h~2h, and then wash it repeatedly with deionized water until the washing solution is neutral. Take out the polyurethane sponge and dry it at a temperature of 60℃~80℃ for 6h~12h to obtain activated polyurethane sponge. The activation treatment aims to hydrolyze some functional groups on the surface of the polyurethane foam, increasing its hydrophilicity and reactive sites. Step 3: Prepare a mixed dispersion by combining dopamine hydrochloride with pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and magnetically stir it at 25℃~40℃ and 100rpm~300rpm for 12h~48h to allow dopamine hydrochloride to undergo a self-polymerization reaction. After the reaction, repeatedly wash until the washing liquid is colorless and transparent, and dry it at 60℃~100℃ for 4h~8h to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material. The preparation process of the mixed dispersion is as follows: Dopamine hydrochloride is dissolved in Tris-HCl buffer with a pH of 8.0~9.0 to obtain a solution with a concentration of 5mg / mL~100mg / mL (this solution is polydopamine (PDA)), and then pretreated halloysite nanotubes are added to the solution and ultrasonically dispersed for 30min~60min to obtain the mixed dispersion. The mass ratio of dopamine hydrochloride to pretreated halloysite nanotubes was 1:0.02~10. Under the self-polymerization reaction conditions of this invention, it is possible to ensure that dopamine hydrochloride is fully oxidized and self-polymerized and uniformly coated.

[0020] The working principle of each step in the preparation method of the halloysite-reinforced polyurethane sponge solar interface evaporation material of the present invention is as follows: The working principle of step 1 is as follows: Calcination mainly initiates the dehydroxylation reaction of halloysite nanotubes, changing their surface chemical state and potentially introducing lattice defects. These defects help broaden the light absorption range and enhance photothermal conversion. Subsequent acid treatment can selectively dissolve the aluminum-oxygen octahedral layer in the halloysite nanotube wall, increasing the abundance of silanol groups on its surface. It may also increase the inner diameter of the tube, enhancing capillary action and providing the halloysite nanotubes with better photothermal activity and more surface binding sites.

[0021] The working principle of step 2 is as follows: Alkali treatment can hydrolyze some of the ester bonds on the surface of polyurethane foam, exposing more polar groups such as carboxyl and amino groups, which improves the hydrophilicity of the foam and facilitates water transport. At the same time, these groups provide more covalent or non-covalent binding sites for the phenolic hydroxyl and amino groups of polydopamine, thereby enhancing the interfacial bonding force.

[0022] The working principle of step 3 is as follows: Dopamine hydrochloride undergoes oxidation, cyclization, and polymerization reactions under weakly alkaline conditions to generate polydopamine (PDA). The catechol and amino functional groups in the PDA molecule can strongly adhere to the polar groups exposed on the activated sponge surface and the abundant silanol and aluminol groups on the surface of the halloysite nanotubes after acid etching through covalent bonds and hydrogen bonds. Through this one-step in-situ polymerization, a strong PDA coating is simultaneously formed on both the halloysite nanotubes and the sponge framework. The PDA forms a rough structure on the surface of the halloysite nanotubes, further enhancing... Strong photothermal performance, realizing the nanoscale tight composite of sponge skeleton, halloysite nanotubes and PDA. Its advantages are simple process, strong bonding force and uniform coating. Step 3 has two functions: (1) PDA is coated on the surface of pretreated halloysite nanotubes, improving its dispersibility and contributing additional photothermal performance; (2) PDA, through its rich catechol and amino groups, forms a strong interaction with the functional groups on the surface of activated sponge and halloysite nanotubes, firmly bridging the two and preparing a stable halloysite-reinforced polyurethane sponge solar interface evaporation material.

[0023] The preparation method of this invention employs a synergistic pretreatment process combining medium-temperature calcination (400℃~600℃) with moderate acid treatment. This process can synergistically regulate the crystal structure, surface chemistry, and pore structure of halloysite nanotubes, maximizing the photothermal performance and interfacial compatibility with PDA without excessively damaging their tubular morphology. This is the foundation for improving the photothermal conversion and water transport of the composite material. Furthermore, by utilizing the in-situ oxidative self-polymerization characteristics of dopamine hydrochloride in a single alkaline buffer system, the coating of halloysite nanotubes and the modification of the polyurethane sponge skeleton are achieved in one step, and the two are simultaneously tightly bonded. This process is simple and efficient, and the resulting PDA interfacial layer has high bonding strength, which is superior to step-by-step coating or physical mixing methods, ensuring the structural integrity of the composite material during long-term evaporation.

[0024] Example 1 Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; The specific process is as follows: Halloysite nanotubes were calcined at 400℃ for 4 hours, cooled, and then sonicated with a 2 mol / L hydrochloric acid solution for 30 minutes. They were then soaked for 2 days, washed with deionized water until neutral, and dried at 70℃ for 10 hours to obtain pretreated halloysite nanotubes. The heating rate was 3℃ / min, and the calcination was carried out in an air atmosphere. The ratio of halloysite nanotubes to hydrochloric acid solution was 1 g: 50 mL. Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; The specific process is as follows: The polyurethane sponge was cut into the required size (2cm×2cm×1cm), ultrasonically cleaned with anhydrous ethanol for 40 minutes to remove surface impurities, squeezed dry, and then soaked in a 2mol / L NaOH solution. During soaking, the polyurethane sponge was squeezed repeatedly to allow the NaOH solution to fully penetrate the sponge pores. Then, it was ultrasonically treated for 2 hours. Afterward, it was repeatedly washed with deionized water until the washing solution was neutral. The polyurethane sponge was then removed and dried at 70℃ for 10 hours to obtain the activated polyurethane sponge. Step 3: Prepare a mixed dispersion by mixing 0.1g dopamine hydrochloride with 0.04g pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and magnetically stir for 30h at 30℃ and 200rpm to allow dopamine hydrochloride to undergo a self-polymerization reaction. After the reaction, repeatedly rinse until the rinsing solution is colorless and transparent, and dry at 80℃ for 6h to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material. The preparation process of the mixed dispersion is as follows: 0.1g of dopamine hydrochloride is dissolved in 20mL of Tris-HCl buffer with a pH of 8.0~9.0 to obtain a solution with a concentration of 5mg / mL. Then, 0.04g of pretreated halloysite nanotubes are added to the solution and ultrasonically dispersed for 40min to obtain the mixed dispersion.

[0025] Example 2 The difference from Example 1 is that in step 1, the calcination temperature is 500°C.

[0026] Example 3 The difference from Example 2 is that in step 1, the calcination temperature is 600°C.

[0027] Example 4 Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; The specific process is as follows: Halloysite nanotubes were calcined at 500℃ for 3 hours, cooled, and then sonicated with a 3 mol / L hydrochloric acid solution for 20 minutes. They were then soaked for 3 days, washed with deionized water until neutral, and dried at 80℃ for 6 hours to obtain pretreated halloysite nanotubes. The heating rate was 5℃ / min, and the calcination was carried out in an air atmosphere. The ratio of halloysite nanotubes to hydrochloric acid solution was 1 g: 50 mL. Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; The specific process is as follows: The polyurethane sponge was cut into the required size (2cm×2cm×1cm), ultrasonically cleaned with anhydrous ethanol for 60 minutes to remove surface impurities, squeezed dry, and then soaked in a 3mol / L NaOH solution. During soaking, the polyurethane sponge was squeezed repeatedly to allow the NaOH solution to fully penetrate the sponge pores. Then, it was ultrasonically treated for 1 hour, and then repeatedly washed with deionized water until the washing solution was neutral. The polyurethane sponge was then removed and dried at 80℃ for 6 hours to obtain the activated polyurethane sponge. Step 3: Prepare a mixed dispersion by mixing 0.1g dopamine hydrochloride with 1g pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and magnetically stir for 12h at 40℃ and 300rpm to allow dopamine hydrochloride to undergo a self-polymerization reaction. After the reaction, rinse repeatedly until the rinsing solution is colorless and transparent, and dry at 100℃ for 4h to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material. The preparation process of the mixed dispersion is as follows: 0.1g of dopamine hydrochloride is dissolved in 10mL of Tris-HCl buffer with a pH of 8.0~9.0 to obtain a solution with a concentration of 10mg / mL. Then, 1g of pretreated halloysite nanotubes is added to the solution and ultrasonically dispersed for 60min to obtain the mixed dispersion.

[0028] Example 5 Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; The specific process is as follows: Halloysite nanotubes were calcined at 600℃ for 2 hours, cooled, and then sonicated with a 1 mol / L hydrochloric acid solution for 40 minutes. They were then soaked for 1 day, washed with deionized water until neutral, and dried at 60℃ for 12 hours to obtain pretreated halloysite nanotubes. The heating rate was 2℃ / min, and the calcination was carried out in an air atmosphere. The ratio of halloysite nanotubes to hydrochloric acid solution was 1 g: 50 mL. Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; The specific process is as follows: The polyurethane sponge was cut into the required size (2cm×2cm×1cm), ultrasonically cleaned with anhydrous ethanol for 20 minutes to remove surface impurities, squeezed dry, and then soaked in a 1mol / L NaOH solution. During soaking, the polyurethane sponge was squeezed repeatedly to allow the NaOH solution to fully penetrate the sponge pores. Then, it was ultrasonically treated for 1 hour, and then repeatedly washed with deionized water until the washing solution was neutral. The polyurethane sponge was then removed and dried at 60℃ for 12 hours to obtain the activated polyurethane sponge. Step 3: Prepare a mixed dispersion by mixing 2g of dopamine hydrochloride and 0.04g of pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and magnetically stir at 25°C and 100rpm for 48h to allow dopamine hydrochloride to undergo a self-polymerization reaction. After the reaction, repeatedly wash until the washing liquid is colorless and transparent, and dry at 60°C for 8h to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material. The preparation process of the mixed dispersion is as follows: 2g of dopamine hydrochloride is dissolved in 20mL of Tris-HCl buffer with a pH of 8.0~9.0 to obtain a solution with a concentration of 100mg / mL. Then, 0.04g of pretreated halloysite nanotubes are added to the solution and ultrasonically dispersed for 30min to obtain the mixed dispersion.

[0029] Example 6 The difference from Example 5 is that in step 3, the mass of dopamine hydrochloride is 2g and the mass of pretreated halloysite nanotubes is 1g.

[0030] Comparative Example 1 The difference from Example 1 is that the step of pretreating halloysite nanotubes in step 1 is omitted, and untreated halloysite nanotubes are used directly to obtain PU / PDA / HNT material.

[0031] Comparative Example 2 The difference from Implementation 1 is that step 1 is omitted; step 3 is as follows: 0.1g of dopamine hydrochloride is dissolved in 20mL of Tris-HCl buffer solution with a pH of 8.0~9.0 to obtain a solution with a concentration of 5mg / mL. The activated polyurethane sponge is immersed in the solution with a concentration of 5mg / mL and magnetically stirred at 30℃ and 200rpm for 30h to allow dopamine hydrochloride to undergo a self-polymerization reaction. After the reaction, the sponge is repeatedly washed until the washing solution is colorless and transparent, and then dried at 80℃ for 6h to obtain the PU / PDA composite material.

[0032] Depend on Figure 1 As can be seen, the specific surface area of ​​halloysite nanotubes increased significantly after calcination and acid treatment.

[0033] Depend on Figure 2 , Figure 3 and Figure 4 As can be seen, halloysite nanotubes treated with different pretreatment methods were successfully loaded onto the PU sponge skeleton and tightly bonded to the PDA coating. Among them, the halloysite nanotube loaded sample (PU / PDA / HNT500) treated at 500℃ showed a more uniform distribution of surface modified materials, and the PDA polymerized on the surface of the halloysite nanotubes to form an uneven surface structure, which is beneficial to light absorption and photothermal conversion.

[0034] Depend on Figure 5 As can be seen, calcination significantly enhances the photothermal performance of the composite material by halloysite nanotubes (HNTs), and this effect is related to the calcination temperature. In Example 3, the halloysite-reinforced polyurethane sponge solar interfacial evaporation material prepared by calcination at 600°C reached its highest equilibrium temperature (approximately 95°C) under illumination, outperforming halloysite nanotube samples calcined at 500°C, 400°C, and uncalcined samples. The principle behind this is that high-temperature calcination reduces infrared thermal radiation loss through dehydroxylation, introduces defect states into the halloysite nanotube lattice to broaden and enhance light absorption, and improves its photothermal conversion efficiency. Simultaneously, calcination also optimizes the surface chemical composition of the halloysite nanotubes, making their interfacial bonding with the PDA stronger, achieving synergistic enhancement of photothermal performance and water transport. This result verifies that pretreatment of halloysite nanotubes is a key innovative step in improving the overall performance of the evaporator.

[0035] Depend on Figure 6As can be seen, calcination significantly improves the solar interface evaporation performance of PU / PDA / HNT, with optimal performance achieved at a medium temperature of 500°C to 600°C. The composite material loaded with calcined halloysite nanotubes (HNT500, HNT600) exhibits the highest and most stable evaporation rate, significantly superior to the uncalcined halloysite nanotube sample. The improvement lies in the synergistic optimization of photothermal conversion and moisture transport achieved by calcination: on one hand, calcination, through dehydroxylation and the introduction of lattice defects, synergistically enhances overall solar absorption and thermal energy conversion with PDA; on the other hand, the moderate calcination temperature, while improving photothermal performance, effectively preserves the hollow capillary structure of the halloysite nanotubes, ensuring that moisture can be rapidly and continuously transported to the evaporation interface via capillary action, avoiding performance degradation due to localized water shortage. Therefore, the essence of the optimal calcination process is finding a key balance between maximizing photothermal conversion efficiency and maintaining efficient capillary water transport capacity.

Claims

1. A method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material, characterized in that, The steps are as follows: Step 1: Pre-treat halloysite nanotubes to obtain pre-treated halloysite nanotubes; Step 2: Pre-treat the polyurethane foam to obtain activated polyurethane foam; Step 3: Prepare a mixed dispersion by combining dopamine hydrochloride with pretreated halloysite nanotubes. Immerse the activated polyurethane sponge in the mixed dispersion and stir magnetically to induce a self-polymerization reaction of dopamine hydrochloride. After the reaction, rinse and dry to obtain halloysite-reinforced polyurethane sponge solar interface evaporation material.

2. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 1, characterized in that, The specific process of step 1 is as follows: calcining halloysite nanotubes at 400℃~600℃ for 2h~4h, then ultrasonically treating them with hydrochloric acid at a concentration of 1mol / L~3mol / L for 20min~40min, followed by soaking for 1 day~3 days, then washing them with deionized water until neutral, and drying them to obtain pretreated halloysite nanotubes.

3. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 1, characterized in that, The specific process of step 2 is as follows: cut the polyurethane sponge into the required size, ultrasonically clean it with anhydrous ethanol to remove surface impurities, then soak it in NaOH solution. During soaking, squeeze the polyurethane sponge repeatedly to allow the NaOH solution to fully penetrate the pores of the sponge, then ultrasonically treat it, and then wash it repeatedly with deionized water until the washing solution is neutral. Take out the polyurethane sponge and dry it to obtain the activated polyurethane sponge.

4. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 3, characterized in that, The ultrasonic cleaning time is 20 min to 60 min, the concentration of NaOH solution is 1 mol / L to 3 mol / L, and the ultrasonic treatment time is 1 h to 2 h.

5. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 1, characterized in that, In step 3, the preparation process of the mixed dispersion is as follows: Dopamine hydrochloride is dissolved in Tris-HCl buffer solution with a pH of 8.0~9.0 to obtain a solution, and then pretreated halloysite nanotubes are added to the solution and ultrasonically dispersed to obtain a mixed dispersion.

6. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 5, characterized in that, The concentration of the solution was 5 mg / mL to 100 mg / mL; the mass ratio of dopamine hydrochloride to pretreated halloysite nanotubes was 1:0.02 to 10.

7. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 5, characterized in that, The ultrasonic dispersion time is 30 min to 60 min.

8. The method for preparing halloysite-reinforced polyurethane sponge solar interface evaporation material according to claim 1, characterized in that, In step 3, the magnetic stirring temperature is 25℃~40℃, the magnetic stirring time is 12h~48h, and the drying temperature is 60℃~100℃.

9. Halloysite-reinforced polyurethane sponge solar interface evaporation material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

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