Stable hygroscopic photothermal core-shell aerogel materials, preparation method and application thereof

Abstract

The application discloses a kind of stable hygroscopic photothermal core-shell aerogel materials, its preparation method and application.The photothermal core-shell aerogel material includes the core with hygroscopic and desorption function and the shell of the core is wrapped;The core includes aerogel framework and the hygroscopic component distributed in the aerogel framework;The shell is at least formed by the surface of the aerogel framework by photothermal material combination, and has porous structure, can be supplied with moisture-containing gas;And, at least the shell is combined with hydrophobic agent, to make the shell have hydrophobicity.The photothermal core-shell aerogel material and its preparation method provided by the application avoid the loss of hygroscopic component by the hygroscopic effect of core and hygroscopic salt, cooperate with the introduction of photothermal hydrophobic shell to improve the strength of aerogel and the stability of hygroscopic component distribution, and the mechanical property and cyclic stability of aerogel are obviously improved, more capable of resisting harsh natural environment.

Description

Technical Field

[0001] This invention relates to the field of nanoporous materials and functional materials, and in particular to a stable, hygroscopic photothermal core-shell aerogel material, its preparation method, and its applications. Background Technology

[0002] Moisture, an indispensable part of Earth's ecosystem, is widely dispersed in nature through transpiration, plant and animal respiration, and industrial moisture emissions. It is estimated that there is approximately 1.3 × 10¹⁶ kg of moisture in the atmosphere, representing a potential freshwater resource. In recent years, researchers have primarily collected and utilized moisture through methods such as adsorption sensing, air-to-water purification, and dehumidification. Among these, atmospheric water collection based on moisture adsorption is a feasible and effective method for both moisture utilization and water collection and purification. On the other hand, to mitigate excessive negative impacts, it is advisable to develop processes and materials that are economical, scalable, environmentally friendly, and energy-efficient.

[0003] Based on this, high moisture absorption can be achieved by loading with hygroscopic salts or combining with biomass materials, resulting in good moisture absorption performance, while also meeting the current social requirements and trends for energy and environmental development. Chinese invention patent CN105780137A discloses a method for preparing ultra-soft, highly hygroscopic silk fibers. Although silk fibers are highly flexible and environmentally friendly, their hygroscopic performance is still poor compared to most hygroscopic materials, with a maximum hygroscopic rate of only 38%. Chinese invention patent CN101417224B discloses a biological desiccant prepared by combining starch and caustic soda. However, the structure of this material is prone to collapse during the hygroscopic process, making it difficult to effectively exert its hygroscopic performance, and its recyclability is poor. Chinese invention patent CN110330749A discloses a hygroscopic polymer as a photothermal conversion material. However, without protection in complex hygroscopic environments, the hygroscopic performance of the material will still be affected. As the hygroscopic-desorption cycle proceeds, the hygroscopic components will be lost or become ineffective. For example, the impact of waves during hygroscopic processes at sea and the erosion of rainwater during hygroscopic processes on land will affect the hygroscopic performance of the material.

[0004] Therefore, although existing technologies provide composite moisture-absorbing materials combining biomass and desiccant, they are difficult to recycle under complex environmental conditions, and the moisture-absorbing components are easily lost. In light of these issues, improving the moisture absorption stability and mechanical properties of moisture-absorbing materials, and ensuring they withstand complex environmental conditions during the moisture absorption-desorption process, is a serious challenge and an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a stable, hygroscopic photothermal core-shell aerogel material, its preparation method, and its applications.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] In a first aspect, the present invention provides a stable hygroscopic photothermal core-shell aerogel material, comprising a core having hygroscopic and desorption functions and a shell enclosing the core; the core comprising an aerogel framework and hygroscopic components distributed in the aerogel framework; the shell being formed at least by photothermal material bonded to the surface of the aerogel framework and having a porous structure that allows moisture-containing gas to pass through; and at least the shell being bonded with a hydrophobic agent to make the shell hydrophobic.

[0008] Secondly, the present invention also provides a method for preparing a stable, hygroscopic, photothermal core-shell aerogel material, comprising:

[0009] A core with hygroscopic and desorption functions is provided, the core comprising an aerogel framework and hygroscopic components distributed in the aerogel framework;

[0010] The core is brought into contact with a processing liquid containing at least a photothermal material and a hydrophobic agent, and the photothermal material and the hydrophobic agent form a shell on the surface of the core to enclose the core.

[0011] The photothermal material is bonded to the surface of the aerogel skeleton to form a porous structure that allows moisture-containing gas to pass through. The hydrophobic agent is bonded to at least the surface of the shell to make the shell hydrophobic.

[0012] Thirdly, the present invention also provides the application of the above-mentioned photothermal core-shell aerogel material in the field of moisture adsorption.

[0013] Specifically, the present invention provides a humidity control method, comprising:

[0014] The gas containing moisture is brought into contact with the above-mentioned photothermal core-shell aerogel material to absorb the moisture in the gas;

[0015] And optionally, the water-absorbing photothermal core-shell aerogel material is heated or irradiated with light to decompose and absorb the water.

[0016] Furthermore, the number of adsorption-desorption cycles mentioned above exceeds 50.

[0017] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0018] 1. In terms of product structure, the mechanical properties of aerogel are significantly improved by introducing a core-shell structure CNF aerogel rigid shell. Due to the protective and hydrophobic properties of the shell, it can resist the effects of harsh environments such as wave impact in marine moisture absorption applications and rain erosion on land, avoiding the loss of moisture-absorbing components, thus achieving stable moisture absorption and desorption.

[0019] 2. Considering product performance, the prepared photothermal core-shell aerogel can achieve stable moisture absorption for up to 50 cycles, while also exhibiting excellent moisture absorption properties (0.5-3.5g). -1 ) and desorption performance (resolution of 0.3-2 kg m under one sunlight) -2 h -1 The compressive strength is increased to 60-100 kPa, which is nearly 4 times higher than the compressive strength of a simple core (15-25 kPa); the outer shell has good hydrophobicity and high light absorption.

[0020] 3. From the perspective of product sustainability and environmental friendliness, the raw materials required for the prepared core-shell CNF aerogel are degradable and highly biocompatible, and will not have a negative impact on the ecological environment, which is in line with the current social requirements for energy and environmental development.

[0021] 4. From the perspective of large-scale production, the preparation method and process of core-shell structured photothermal core-shell aerogel materials are simple, requiring no expensive preparation instruments, high temperature treatment and catalysts, etc., and are low in cost and time, thus having good prospects for large-scale preparation and application.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0023] Figure 1 These are the overall and local structural characterization test diagrams of the photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0024] Figure 2 This is a test diagram of the compressibility of a photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0025] Figure 3a This is a moisture absorption characterization test diagram of a photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0026] Figure 3b This is a contact angle characterization test diagram of a photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0027] Figure 3c This is a characterization test chart of the desorption rate of a photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0028] Figure 3d This is an absorbance characterization test chart of a photothermal core-shell aerogel material provided in a typical embodiment of the present invention;

[0029] Figure 4 This is a typical embodiment of the present invention, which provides a moisture absorption cycle performance test of a photothermal core-shell aerogel material;

[0030] Figure 5 This is a test diagram of the compressive strength of a photothermal core-shell aerogel material provided in a typical comparative case of the present invention;

[0031] Figure 6 This is a test diagram of the hygroscopic properties of core-shell CNF aerogels with different calcium chloride mass ratios provided in another typical embodiment of the present invention;

[0032] Figure 7 This is an optical photograph of core-shell CNF aerogels with different calcium chloride mass ratios after moisture absorption, provided in another typical embodiment of the present invention;

[0033] Figure 8 This is a test chart of the desorption amount of photothermal core-shell aerogel material under different light intensities after moisture absorption at 90% relative humidity, provided in another typical embodiment of the present invention;

[0034] Figure 9 This is a test chart of the desorption rate of the photothermal core-shell aerogel material under different light intensities after moisture absorption at 90% relative humidity, provided in another typical embodiment of the present invention. Detailed Implementation

[0035] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0037] This invention provides a stable, hygroscopic photothermal core-shell aerogel material, comprising a core with hygroscopic and desorption functions and an outer shell enclosing the core; the core comprises an aerogel framework and hygroscopic components distributed in the aerogel framework; the outer shell is formed by at least a photothermal material bonded to the surface of the aerogel framework and has a porous structure that allows moisture-containing gases to pass through; and at least the outer shell is bonded with a hydrophobic agent to make the outer shell hydrophobic.

[0038] To address the problems in existing technologies, this invention essentially provides a method for preparing and applying a stable, hygroscopic photothermal core-shell aerogel. The resulting core-shell aerogel exhibits significantly improved performance. The synergistic hygroscopic effect of the core and hygroscopic salts, along with the introduction of a photothermal hydrophobic shell, prevents the loss of hygroscopic components and enhances the aerogel's strength and stability. Furthermore, the mechanical properties of the aerogel are significantly improved, making it more resistant to harsh natural environments. Specifically, due to the protective and hydrophobic properties of the shell, it can withstand the effects of harsh environments such as wave impacts during marine hygroscopic processes and rain erosion during terrestrial hygroscopic processes. Internally, it prevents the loss of hygroscopic components, thus achieving stable hygroscopic-desorption. Simultaneously, the prepared core-shell CNF aerogel has a simple and inexpensive preparation process, meeting the needs of industrial production and aligning with current societal requirements for energy and environmental development.

[0039] It is worth noting that the photothermal core-shell aerogel material provided in this embodiment of the invention can not only be regarded as a physical shell that only has a protective and photothermal function to wrap the hygroscopic aerogel material (core). There is also a microscopic interaction between the shell and the core, especially the hydrophobic property. This hydrophobic property not only resists the erosion of the core by external moisture, but also resists the loss of internal hygroscopic components. It prevents the diffusion of the hygroscopic components and water mixture towards the shell after absorbing moisture (the microscopic transport of moisture causes the hygroscopic components to be gradually carried to the surface of the aerogel in the hygroscopic-desorption cycle). Combined with the strong binding effect of the aerogel skeleton on the hygroscopic components, the stability of the microscopic component distribution of the aerogel structure is significantly improved, thus bringing about an improvement in both internal and external stability.

[0040] In some embodiments, the photothermal material includes polymer materials and / or photothermal nanomaterials;

[0041] In some embodiments, the polymer material includes any one or a combination of two or more of polypyrrole, polyethylene glycol, polyazobenzene, and polythiophene; the polymer material may be bonded to the surface of the aerogel framework, for example, by oxidative polymerization or other various forms of initiated polymerization.

[0042] In some embodiments, the photothermal nanomaterial may further include any one or a combination of two or more of CNTs, MXene, graphene oxide, and graphene. When the above-mentioned inorganic carbon materials or nanomaterials are selected alone, they can be bonded to the surface of the aerogel framework through silane coupling, or they can be combined with polymer material monomers to simultaneously fix the above-mentioned nanomaterials to the surface during polymer polymerization and deposition.

[0043] In some embodiments, the hydrophobic agent comprises a silane coupling agent, preferably a silane coupling agent having a fluorine-substituted group;

[0044] In some embodiments, the silane coupling agent comprises any one or a combination of two or more of 1H,2H,2H-perfluorodecyltriethoxysilane, Γ-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0045] In some embodiments, the aerogel framework is made of any one or a combination of two or more of cellulose nanofibers, sodium alginate nanofibers, bacterial cellulose, and polyvinyl alcohol fibers.

[0046] In some embodiments, the hygroscopic component includes a hygroscopic salt, and in some embodiments, it may specifically include any one or a combination of two or more of lithium chloride, lithium bromide, calcium chloride, magnesium chloride, and copper sulfate.

[0047] In some embodiments, the mass fraction of the hygroscopic component in the core is 5-40%.

[0048] This invention also provides a method for preparing a stable, hygroscopic photothermal core-shell aerogel material, comprising the following steps:

[0049] A core with hygroscopic and desorption functions is provided, the core comprising an aerogel framework and hygroscopic components distributed in the aerogel framework;

[0050] The core is brought into contact with a processing liquid containing at least a photothermal material and a hydrophobic agent, and the photothermal material and the hydrophobic agent form a shell on the surface of the core to enclose the core.

[0051] The photothermal material is bonded to the surface of the aerogel skeleton to form a porous structure that allows moisture-containing gas to pass through. The hydrophobic agent is bonded to at least the surface of the shell to make the shell hydrophobic.

[0052] In some implementation schemes, the following steps are specifically included:

[0053] The aerogel framework is formed by treating the precursor liquid containing dispersed nanofiber materials using a cryotemplate method.

[0054] The aerogel framework is brought into contact with a solution of the hygroscopic component, and the solvent is removed so that the hygroscopic component is incorporated into the interior of the aerogel framework.

[0055] In some embodiments, the photothermal material is selected from polypyrrole, and the preparation method may further include the following steps:

[0056] Prepare a treatment solution containing pyrrole and the hydrophobic agent, and make the treatment solution fully contact the surface of the core so that the pyrrole and the hydrophobic agent are loaded on the surface of the core;

[0057] The core loaded with pyrrole and a hydrophobic agent is brought into contact with an oxidant to undergo oxidative polymerization, causing the pyrrole to polymerize into polypyrrole. The polypyrrole is bonded to the surface of the aerogel skeleton, and the hydrophobic agent is bonded to the surface of the polypyrrole to form the outer shell.

[0058] In some embodiments, the mass fraction of the photothermal material in the treatment liquid is 30-98%; the mass ratio of the photothermal material to the hydrophobic agent is 50:1-10:1.

[0059] As some typical application examples of the above technical solutions, taking CNF (cellulose nanofiber) as the base material as an example, the preparation process of its aerogel generally includes: 1. Preparation of the core-shell structure aerogel core-CNF aerogel; 2. Loading of hygroscopic salts in CNF aerogel; 3. Preparation of photothermal shell and hydrophobic treatment of shell, etc.

[0060] The specific preparation process is as follows:

[0061] (1) First, stir and sonicate 0.4-1.6 wt.% CNF dispersion with ethanol in a certain ratio for 10-30 min to obtain CNF dispersion raw material; the mass ratio of CNF dispersion to ethanol is 100:1-10:1.

[0062] (2) Next, the CNF dispersion raw material prepared in step (1) is poured into a mold and frozen to obtain CNF ice gel, and then placed in a freeze dryer to freeze dry to obtain CNF aerogel.

[0063] (3) Spray a certain mass ratio of hygroscopic salt solution onto the CNF aerogel from step (2) to fully load the hygroscopic salt into the CNF aerogel. After impregnation, transfer it to an oven to dry the surface of the aerogel and remove the moisture from the surface of the aerogel. The raw material of the hygroscopic salt is one of lithium chloride, lithium bromide, calcium chloride, magnesium chloride and copper sulfate. The mass fraction of the hygroscopic salt is 5-40 wt.%.

[0064] (4) After drying the CNF aerogel surface in step (3), completely immerse it in a mixture of 1H,2H,2H-perfluorodecyltriethoxysilane and photothermal material; the photothermal material can be one of CNT, MXene, pyrrole and graphene oxide; the concentration of the photothermal material is 30-98 wt.%; the mass ratio of the photothermal material to 1H,2H,2H-perfluorodecyltriethoxysilane is 50:1-10:1.

[0065] (5) Taking pyrrole as an example of photothermal material, the CNF aerogel soaked in step (4) is placed in an oxidant for oxidative polymerization for 0.5-3 hours. During the polymerization process, the surface of CNF aerogel will gradually turn black and eventually form a black hydrophobic hard shell. The oxidant can be one of hydrogen peroxide, ammonium persulfate, ferric chloride and sodium hypochlorite. The concentration of the oxidant solution is 0.05-2M.

[0066] (6) Finally, the CNF aerogel that has undergone surface oxidation polymerization in (5) is dried in an oven at 50-100℃ for 0.5-3h to remove moisture from the aerogel and obtain the desired core-shell CNF aerogel.

[0067] As a further extension of the above technical solution, the embodiments of the present invention also provide the application of the photothermal core-shell aerogel material provided in any of the above embodiments in the field of moisture adsorption.

[0068] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0069] Example 1

[0070] This embodiment illustrates the preparation, structural characterization, and hygroscopic-desorption performance testing of a core-shell CNF aerogel, as detailed below:

[0071] (1) First, mix 1 wt.% TEMPO-CNF dispersion with ethanol at a ratio of 60:1, stir and sonicate for ~30 min to obtain CNF dispersion raw material;

[0072] (2) Next, the TEMPO-CNF dispersion raw material prepared in (step 1) is poured into a mold and frozen at -20°C to obtain TEMPO-CNF ice gel. Then, it is freeze-dried in a freeze dryer to obtain TEMPO-CNF aerogel.

[0073] (3) Spray TEMPO-CNF aerogel with 20wt.% lithium chloride solution to fully load lithium chloride into TEMPO-CNF aerogel. After impregnation, transfer it to an oven to dry the surface of the aerogel and remove the moisture from the surface of the aerogel.

[0074] (4) After drying the surface of the TEMPO-CNF aerogel in step (3), completely immerse it in a mixture containing 60 wt.% pyrrole in 1H,2H,2H-perfluorodecyltriethoxysilane (mass ratio ~40:1);

[0075] (5) Place the TEMPO-CNF aerogel soaked in (4) into a 0.1M ferric chloride solution for oxidative polymerization for 2 hours. During the polymerization process, the surface of the TEMPO-CNF aerogel will gradually turn black and eventually form a hydrophobic photothermal hard shell.

[0076] (6) Finally, the TEMPO-CNF aerogel that was surface oxidized and polymerized in (5) was dried in an oven at 80°C for 2 hours to remove moisture from the aerogel and obtain the desired core-shell TEMPO-CNF aerogel.

[0077] Characterization tests:

[0078] The core-shell structured TEMPO-CNF aerogel prepared by this strategy has distinct layers and a uniform morphology, such as... Figure 1 As shown, the core TEMPO-CNF aerogel has a porous structure and lithium chloride crystals are uniformly distributed on the pore walls, while the outer photothermal layer wraps around the surface of the TEMPO-CNF aerogel; and Figure 2 This indicates that the prepared core-shell structured TEMPO-CNF aerogel has excellent compressibility (~85 kPa).

[0079] The core-shell structured TEMPO-CNF aerogel prepared by this strategy can be used for hygroscopic and desorption water collection in gases. Figures 3a-3d It is known that the maximum moisture absorption capacity is ~3g. -1 The desorption rate under one sun is ~1.8 kg m³. -2 h -1 Meanwhile, the outer shell has good hydrophobicity (contact angle ~150°) and high light absorption (~96%).

[0080] The core-shell structured TEMPO-CNF aerogel prepared by this strategy underwent hygroscopic desorption cycle testing at an ambient humidity of RH~70%, as shown in the figure. Figure 4 As shown, in 50 cycles of moisture absorption-desorption testing, the core-shell structured TEMPO-CNF aerogel maintained a moisture absorption capacity of 1.6-1.8 g / L due to the protective effect of the outer shell's hydrophobicity to both the inside and outside of the shell and its high compressive strength. -1 In a relatively stable state, it exhibits excellent cyclic moisture absorption stability and can achieve stable cyclic moisture absorption.

[0081] Comparative Example 1

[0082] Compared with Example 1, the CNF moisture-absorbing aerogel without a shell structure was tested for compressive strength and moisture absorption cycle stability.

[0083] (1) First, mix 1 wt.% TEMPO-CNF dispersion with ethanol at a ratio of 60:1, stir and sonicate for ~30 min to obtain CNF dispersion raw material;

[0084] (2) Next, the TEMPO-CNF dispersion raw material prepared in (step 1) is poured into a mold and frozen at -20°C to obtain TEMPO-CNF ice gel. Then, it is freeze-dried in a freeze dryer to obtain TEMPO-CNF aerogel.

[0085] (3) Spray TEMPO-CNF aerogel with 20wt.% lithium chloride solution to fully load lithium chloride into TEMPO-CNF aerogel. After impregnation, transfer it to a 50℃ oven for 3h to dry the aerogel and remove moisture. Finally, the desired TEMPO-CNF hygroscopic aerogel is obtained.

[0086] Characterization tests:

[0087] Depend on Figure 5 It is known that the compressive strength of quaternized CNF hygroscopic aerogel is ~25 kPa, which is nearly 4 times lower than that of core-shell CNF aerogel (~85 kPa).

[0088] The hygroscopic cycle stability of the quaternized CNF hygroscopic aerogel prepared by this strategy was tested. Figure 4 It is known that, since quaternized CNF hygroscopic aerogels lack the hydrophobic and protective properties of an outer shell, the hygroscopic components are gradually lost during repeated hygroscopic-desorption cycles, resulting in a gradual decrease in hygroscopic performance. The hygroscopic capacity decreases from ~2g / g during the cycle. -1 Reduced to ~1.2 gg -1 During the cyclic moisture absorption process, the moisture absorption performance decreased significantly. This indicates that the hydrophobic and protective properties of the outer shell play a crucial role in the moisture absorption stability of the quaternized CNF aerogel.

[0089] Comparative Example 2

[0090] This comparative example is largely the same as Example 1, with the main difference being:

[0091] After CNF aerogel is prepared in step (3), the aerogel is tightly wrapped with a porous (micron-sized pores) hydrophobic film made of polytetrafluoroethylene. Then, a hygroscopic-desorption cycle experiment is carried out. The results are very similar to those of Comparative Example 1. The physically wrapped shell is completely unable to resist the movement of water and drive the hygroscopic salt to the outside of the aerogel. A large amount of hygroscopic salt will accumulate in the gap between the physically wrapped shell and the core.

[0092] Comparative Example 3

[0093] This comparative example is largely the same as Example 1, with the main difference being:

[0094] After CNF aerogel was prepared in step (3), the surface of the aerogel was coated with polytetrafluoroethylene coating and dried. Micron-sized pores were then laser-drilled to achieve a porous structure for water vapor to pass through. Then, a moisture absorption-desorption cycle experiment was conducted. The results were very similar to those of Comparative Example 1. This shows that even though the hydrophobic film was bonded to the surface of the aerogel core in a more tighter way than that of Comparative Example 2, the microscopic bonding structure between the hydrophobic photothermal material and the aerogel skeleton in the core was not formed, and it was impossible to resist the migration of internal salts.

[0095] Example 2

[0096] This example illustrates the effect of the hygroscopic salt mass ratio on the hygroscopic properties of the core and the hydrophobicity of the shell in a core-shell CNF aerogel, as shown below:

[0097] (1) First, 0.8 wt.% sulfonated CNF dispersion and ethanol were stirred and sonicated for 30 min at a ratio of 40:1 to obtain sulfonated CNF dispersion raw material;

[0098] (2) Next, the raw materials of the sulfonated CNF layer dispersion prepared in (1) were poured into 5 molds of the same size and frozen at -20°C to obtain sulfonated CNF ice gel. Then, they were placed in a freeze dryer to freeze dry and obtain sulfonated CNF aerogel.

[0099] (3) Spray 5 sulfonated CNF aerogels with 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.% and 30 wt.% calcium chloride solution respectively, so that calcium chloride is fully loaded into the sulfonated CNF aerogels. After impregnation, transfer them to an oven to dry the surface of the aerogels to remove the moisture on the surface of the aerogels.

[0100] (4) After drying the surfaces of the sulfonated CNF aerogels with five different calcium chloride mass ratios in (3), they were completely immersed in a mixture of 90 wt.% pyrrole in 1H, 2H, 2H-perfluorodecyltriethoxysilane (mass ratio 30:1).

[0101] (5) Five sulfonated CNF aerogels with different lithium chloride mass ratios after soaking in (4) were placed in 1M hydrogen peroxide solution for oxidative polymerization for 1 hour. During the polymerization process, the surface of the sulfonated CNF aerogel will gradually turn black and eventually form a black hydrophobic photothermal hard shell.

[0102] (6) Finally, the sulfonated CNF aerogel with surface oxidation polymerization in (5) was dried in an oven at 90°C for 1 hour to remove moisture from the aerogel and obtain the core-shell sulfonated CNF aerogel with the required 5 different calcium chloride mass ratios.

[0103] Characterization tests:

[0104] Core-shell sulfonated CNF aerogels with different calcium chloride mass ratios were prepared. The variation in the calcium chloride mass ratio affected the hygroscopic properties of the core and the hydrophobicity of the outer shell of the core-shell sulfonated CNF aerogels. Figure 6 As shown, with the increase of calcium chloride mass ratio, more hygroscopic components are introduced, leading to a gradual increase in the moisture absorption of core-shell sulfonated CNF aerogels; however, excessive calcium chloride can also affect the hydrophobic properties of the aerogel shell, such as... Figure 7 As shown, when the calcium chloride mass ratio is higher than 15 wt.% (20 wt.% and 30 wt.%), the excessive hygroscopic component content exceeds the hygroscopic load of the core-shell sulfonated CNF aerogel, leading to excessive calcium chloride and moisture leakage onto the surface, affecting the surface hydrophobic structure and deteriorating hydrophobic properties. By comparing with Experimental Example 1, it was determined that while ensuring the hygroscopic performance of the core-shell sulfonated CNF aerogel, the hydrophobic properties and structural stability of the aerogel shell must also be guaranteed. Through comparison, the core-shell CNF aerogel prepared with 15 wt.% calcium chloride was ultimately selected. At this point, while ensuring the hydrophobic properties of the shell, the hygroscopic load under RH~95% conditions was ~3 g / g. -1 Meanwhile, the photothermal core-shell structured aerogel prepared in this way can achieve stable moisture absorption for up to 50 cycles.

[0105] Example 3

[0106] Compared with Example 1, the photothermal desorption performance of core-shell CNF aerogel under different light intensities was tested.

[0107] (1) First, stir and sonicate 1.2 wt.% bacterial CNF dispersion with ethanol at a ratio of 80:1 for 25 min to obtain bacterial CNF dispersion raw material;

[0108] (2) Next, the bacterial CNF dispersion raw material prepared in (1) was poured into a mold and frozen at -20°C to obtain bacterial ice gel. Then, it was placed in a freeze dryer to freeze dry and obtain bacterial aerogel.

[0109] (3) Spray the bacterial CNF aerogel into a 10wt.% lithium bromide solution for 8 minutes to allow the lithium bromide to be fully loaded into the bacterial CNF aerogel. After impregnation, transfer it to a 100℃ oven for 0.5 hours to dry the surface of the aerogel and remove the moisture from the surface of the aerogel.

[0110] (4) After drying the surface of the bacterial CNF aerogel in (3), completely immerse it in a mixture of 30 wt.% MXene and 1H,2H,2H-perfluorodecyltriethoxysilane (mass ratio ~10:1);

[0111] (5) Place the bacterial CNF aerogel soaked in (4) in a 0.1M ammonium persulfate solution for 3 hours. During this period, the surface of the bacterial CNF aerogel will gradually turn black and eventually form a black hydrophobic hard shell.

[0112] (6) Finally, the bacterial CNF aerogel with surface oxidation polymerization in (5) is dried in an oven at 60°C for 1.5 hours to remove moisture from the aerogel and obtain the desired core-shell bacterial CNF aerogel.

[0113] Characterization test

[0114] The core-shell bacterial CNF aerogel prepared by this strategy, after absorbing moisture at 90% relative humidity, underwent photothermal desorption at solar intensities of 0.6, 0.8, 1.0, and 1.2, respectively. Figure 8 It can be seen that the desorption performance improves with increasing light intensity, and the desorption time is shortened for the same desorption amount. From Figure 9 It can be seen that the desorption rate further increases with increasing light intensity, from ~0.7 kg m -2 h -1 Increased to ~2.7kg m -2 h -1 Both can achieve stable moisture absorption-desorption cycles of up to 50 times.

[0115] Based on the above embodiments and comparative examples, it is clear that the embodiments of the present invention, through the synergistic hygroscopic effect of the core and hygroscopic salts, and the introduction of a photothermal hydrophobic shell, avoid the loss of hygroscopic components and improve the strength and stability of the hygroscopic component distribution of the aerogel. Furthermore, the mechanical properties and cycle stability of the aerogel are significantly enhanced, making it more resistant to harsh natural environments. Specifically, due to the protective and hydrophobic properties of the shell, it can resist the effects of harsh environments such as wave impacts during marine hygroscopic processes and rain erosion during terrestrial hygroscopic processes, while internally preventing the loss of hygroscopic components, thus achieving stable hygroscopic-desorption. Simultaneously, the prepared core-shell CNF aerogel has a simple preparation process and low cost, meeting the needs of industrial production and aligning with current societal requirements for energy and environmental development.

[0116] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A stable, hygroscopic, photothermal core-shell aerogel material, characterized in that, It includes a core with moisture absorption and desorption functions and an outer shell that encloses the core; The core comprises an aerogel framework and a hygroscopic component distributed within the aerogel framework; The outer shell is formed by at least photothermal material bonded to the surface of the aerogel skeleton and has a porous structure that allows gas containing moisture to pass through. In addition, at least the outer shell is coated with a hydrophobic agent to make the outer shell hydrophobic, the hydrophobicity preventing the diffusion of the hygroscopic component and the water mixture after absorbing moisture toward the outer shell; The preparation method of the stable, hygroscopic, photothermal core-shell aerogel material includes the following steps: A core with hygroscopic and desorption functions is provided, the core comprising an aerogel framework and hygroscopic components distributed in the aerogel framework; The core is brought into contact with a processing liquid containing at least a photothermal material and a hydrophobic agent, and the photothermal material and the hydrophobic agent form a shell on the surface of the core to enclose the core. The photothermal material is bonded to the surface of the aerogel skeleton to form a porous structure that allows moisture-containing gas to pass through. The hydrophobic agent is bonded to at least the surface of the shell to make the shell hydrophobic.

2. The photothermal core-shell aerogel material according to claim 1, characterized in that, The photothermal material includes polymer materials and / or photothermal nanomaterials. The polymer materials include any one or a combination of two or more of polypyrrole, polyethylene glycol, polyazobenzene, and polythiophene. The photothermal nanomaterials include any one or a combination of two or more of CNT, MXene, graphene oxide, and graphene.

3. The photothermal core-shell aerogel material according to claim 1, characterized in that, The hydrophobic agent includes a silane coupling agent.

4. The photothermal core-shell aerogel material according to claim 3, characterized in that, The silane coupling agent includes any one or a combination of two or more of 1H,2H,2H-perfluorodecyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

5. The photothermal core-shell aerogel material according to claim 1, characterized in that, The aerogel framework is made of any one or a combination of two or more of the following materials: cellulose nanofibers, sodium alginate nanofibers, bacterial cellulose, and polyvinyl alcohol fibers. The hygroscopic component includes a hygroscopic salt, which includes any one or a combination of two or more of lithium chloride, lithium bromide, calcium chloride, magnesium chloride, and copper sulfate.

6. The photothermal core-shell aerogel material according to claim 5, characterized in that, The mass fraction of the hygroscopic component in the core is 5-40%.

7. The photothermal core-shell aerogel material according to claim 1, characterized in that, The preparation method specifically includes: The aerogel framework is formed by treating the precursor liquid containing dispersed nanofiber materials using a cryotemplate method. The aerogel framework is brought into contact with a solution of the hygroscopic component, and the solvent is removed, so that the hygroscopic component is incorporated into the interior of the aerogel framework to obtain the core.

8. The photothermal core-shell aerogel material according to claim 1, characterized in that, The photothermal material is selected from polypyrrole, and the preparation method specifically includes: Prepare a treatment solution containing pyrrole and the hydrophobic agent, and make the treatment solution fully contact the surface of the core so that the pyrrole and the hydrophobic agent are loaded on the surface of the core; The core loaded with pyrrole and a hydrophobic agent is brought into contact with an oxidant to undergo oxidative polymerization, causing the pyrrole to polymerize into polypyrrole. The polypyrrole is bonded to the surface of the aerogel skeleton, and the hydrophobic agent is bonded to the surface of the polypyrrole to form the outer shell.

9. The photothermal core-shell aerogel material according to claim 1, characterized in that, The mass fraction of photothermal material in the treatment solution is 30-98%; the mass ratio of photothermal material to hydrophobic agent is 50:1-10:

1.

10. The application of the photothermal core-shell aerogel material according to any one of claims 1-9 in the field of moisture adsorption.

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