CN118598251A - A nanocellulose-based solar interface evaporation device, preparation method and use thereof - Google Patents

Abstract

The invention provides a nanocellulose-based solar interface evaporation device, a preparation method and application thereof, which are characterized in that quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and nanocellulose solution are used as gel precursor solutions, photo-thermal conversion materials consisting of graphene oxide and copper sulfide and modified Mxene nanosheets modified by polyethyleneimine and polydopamine are added into the gel precursor solutions, a composite hydrogel with a good framework structure is constructed through hydrogen bond crosslinking and freeze thawing circulation, then chemical in-situ polymerization is utilized, aniline monomers are initiated to grow in situ in the composite hydrogel to generate polyaniline nanofibers, an aerogel matrix with vertically arranged macroporous channels is obtained through directional freeze drying, finally polypyrrole is generated on the surface of the aerogel matrix through in-situ polymerization reaction, and the polypyrrole is used as a light absorption site, so that the light capturing capability of the solar interface evaporation device is remarkably improved.

Description

A nanocellulose-based solar interface evaporation device, preparation method and use thereof

Technical Field

The invention belongs to the technical field of seawater desalination and relates to a nanocellulose-based solar interface evaporation device, a preparation method and application thereof.

Background Art

Freshwater resources are the foundation of human survival and play a decisive role in important pillar industries of the national economy such as industry and food production. At present, the technology that is considered most likely to solve the problem of freshwater shortage is seawater desalination technology. The more mature seawater desalination technologies include distillation, electrodialysis, osmosis and freezing.

Solar-driven interfacial water evaporation technology, in simple terms, uses solar energy as "power" and absorbs solar energy and converts it into heat energy through the design of photothermal conversion materials, heating water to produce water vapor. When the solar-driven interfacial water evaporation system is applied to seawater desalination, fresh water resources can be obtained by simply collecting the generated water vapor, without the need for large-scale production equipment and avoiding the consumption of fossil energy.

The low thermal conductivity of nanocellulose aerogel can avoid energy waste, while the porous structure can enhance the multiple reflections of sunlight and thus enhance the material's absorption of solar energy. In addition, the excellent hydrophilicity of nanocellulose aerogel can ensure the rapid transmission of water. Due to the above advantages, nanocellulose aerogel is considered to be the most excellent base support material for solar water evaporators. However, nanocellulose aerogel itself does not absorb sunlight, so it needs to be combined with other photothermal materials to obtain excellent water vapor evaporation performance.

Summary of the invention

In view of the shortcomings of the prior art, the object of the present invention is to provide a nanocellulose-based solar interface evaporation device, a preparation method and use thereof.

To achieve this object, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for preparing a nanocellulose-based solar interface evaporation device, the preparation method comprising:

(I) dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion liquid after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion liquid, and mixing and stirring under sealed conditions until the L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution to the reaction solution, and mixing uniformly to obtain a precursor solution, and transferring the precursor solution to a reactor for heating, so that L-cysteine and copper chloride react to generate copper sulfide, and at the same time, the graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, the reaction product is filtered, washed and dried to obtain a photothermal conversion material composed of reduced graphene oxide and copper sulfide;

(II) adding lithium fluoride to a hydrochloric acid solution, mixing well to obtain an etching solution, adding titanium aluminum carbide powder to the etching solution, stirring magnetically and heating in a water bath to obtain a suspension, washing the suspension with deionized water and centrifuging in sequence, repeating the washing and centrifuging operations at least three times, dispersing the precipitate in deionized water, letting it stand, and drying the supernatant to obtain Mxene nanosheets; dispersing the Mxene nanosheets in deionized water to form an Mxene dispersion, transferring the Mxene dispersion to a shaker, adding polyethyleneimine to the Mxene dispersion, and heating and shaking in a shaker to perform amino modification; subsequently, adding a dopamine solution to the Mxene dispersion at room temperature, mixing and shaking in a shaker to allow dopamine to undergo in-situ oxidation self-polymerization to form polydopamine, and finally filtering, washing, and drying to obtain modified Mxene nanosheets;

(III) dispersing chitosan in an acetic acid aqueous solution, mixing and stirring, and heating until the chitosan is completely dissolved to obtain a chitosan solution, dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution, mixing and stirring, and heating to quaternize the chitosan, and then filtering, washing, and drying to obtain quaternized chitosan; uniformly mixing polyvinyl alcohol, glycerol, and deionized water to obtain a reaction precursor solution, heating the reaction precursor solution to reflux reaction, filtering, washing, and drying after the reaction to obtain modified polyvinyl alcohol; dissolving sodium alginate in deionized water to obtain a sodium alginate solution, adding sodium periodate to the sodium alginate solution, stirring at room temperature and in the dark to cause an oxidation reaction, and filtering, washing, and drying after the reaction to obtain oxidized sodium alginate;

(IV) adding the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate obtained in step (III) to the nanocellulose solution, mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (I) and the modified Mxene nanosheets obtained in step (II) to the precursor mixed solution, and obtaining a gel precursor solution after ultrasonic dispersion;

(V) mixing glutaraldehyde and hydrochloric acid solution uniformly to obtain glutaraldehyde acid solution, pouring the gel precursor solution obtained in step (IV) into a mold, dropping the glutaraldehyde acid solution into the gel precursor solution, mixing and stirring to cause a cross-linking reaction, and standing at room temperature after the reaction to gel to obtain a hydrogel intermediate; freezing the hydrogel intermediate under low temperature conditions for a period of time, then taking it out and thawing it for a period of time, repeating the freezing and thawing process at least three times to obtain a composite hydrogel;

(VI) immersing the composite hydrogel obtained in step (V) in an aniline monomer solution, dropping an ammonium persulfate solution into the aniline monomer solution, mixing and stirring, and then standing to react to generate polyaniline. After the reaction is completed, filtering, washing and drying are performed in sequence to obtain a modified composite hydrogel, placing the modified composite hydrogel on a cold plate for directional freezing, contacting one side of the modified composite hydrogel with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel, and after being placed on the cold plate for a period of time, removing the modified composite hydrogel and placing it in a freeze dryer for freeze drying to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix;

(VII) dissolving pyrrole monomer in hydrochloric acid solution, mixing evenly to obtain pyrrole monomer solution, immersing the aerogel matrix obtained in step (VI) in the pyrrole monomer solution and performing magnetic stirring to allow the pyrrole monomer to enter the pores of the aerogel matrix; subsequently, adding ferric chloride solution to the pyrrole monomer solution, performing magnetic stirring in an ice-water bath environment to react, so that the pyrrole monomer undergoes in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole, and after the reaction is completed, filtering, washing and liquid nitrogen freeze-drying to obtain the nanocellulose-based solar interface evaporation device.

The invention uses quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and nanocellulose solution as gel precursor solution, adds photothermal conversion material composed of graphene oxide and copper sulfide and modified Mxene nanosheets modified by polyethyleneimine and polydopamine into the gel precursor solution, and constructs a composite hydrogel with a good skeleton structure through hydrogen bond crosslinking and freeze-thaw cycle under the action of glutaraldehyde crosslinking agent; then, chemical in-situ polymerization is used, and ammonium persulfate is used as an oxidant to induce in-situ growth of aniline monomer inside the composite hydrogel to generate polyaniline nanofibers; through directional freeze drying, an aerogel matrix with vertically arranged macroporous channels is obtained; finally, pyrrole in-situ polymerization reaction is performed on the surface of the aerogel matrix to generate polypyrrole; the polypyrrole, as a light absorption site, significantly improves the light capture ability of a solar interface evaporation device, helps to achieve wide absorption of the solar interface evaporation device in the full spectrum range, and improves the utilization rate of sunlight by the solar interface evaporation device.

The main factors affecting the water evaporation rate of the solar interface evaporation device include the structural design of the solar interface evaporation device and the photothermal conversion material with excellent light absorption performance. Reduced graphene oxide has a large specific surface area, good photothermal conversion performance and excellent thermal stability. Its solar-thermal conversion efficiency is as high as 90.1%, and its solar-steam conversion efficiency is as high as 96.2%. Since copper sulfide has a strong light absorption capacity in the near-infrared region, the present invention combines reduced graphene oxide with copper sulfide, and utilizes the synergistic effect between the two, which greatly improves the utilization rate of sunlight by the solar interface evaporation device.

Copper sulfide is a p-type semiconductor material. It exhibits excellent photothermal conversion performance due to copper vacancies in the crystal lattice. The plasma resonance effect causes the migration of surface carriers. Currently, the preparation of copper sulfide materials mostly uses sodium sulfide, thiourea and dimethyl sulfoxide as sulfur sources, which requires the use of a large amount of chemical reagents. The present invention adopts biomass amino acid L-cysteine as a sulfur source and copper chloride as a copper source. L-cysteine plays a triple role of a reducing agent, a sulfur supplying agent and a connecting agent in the hydrothermal reaction process. On the one hand, L-cysteine contains a carboxyl group (-COOH), a thiol group (-SH) and an amino group (-NH ₂ ). Due to the presence of -SH, it has a high affinity for Cu ²⁺ ions. In the hydrothermal reaction process, L-cysteine releases H ₂ S, which serves as a sulfide source to form metal sulfide nanoparticles with Cu ²⁺ . On the other hand, L-cysteine can also serve as a reducing agent to reduce graphene oxide to reduced graphene oxide. On the other hand, since nano copper sulfide is not easy to disperse, L-cysteine is used as a connecting agent to load the copper sulfide generated by the reaction on the graphene oxide sheet, and the copper sulfide/reduced graphene oxide photothermal conversion material is synthesized in one step through the hydrothermal reaction.

The synergistic effect between reduced graphene oxide and copper sulfide is reflected in:

On the one hand, the local surface plasmon resonance effect of copper sulfide and the process of electron transition between the conduction band and the valence band (1.2~2.0eV) help the solar interface evaporation device to achieve wide absorption in the full spectrum range, thereby obtaining a higher surface temperature, which is beneficial to increase the water evaporation rate on the surface of the solar interface evaporator. In addition, copper sulfide and reduced graphene oxide both have excellent light absorption capabilities. The electronic interaction between reduced graphene oxide and copper sulfide can also further reduce the band gap of copper sulfide, so that more photons are absorbed, thereby improving the utilization rate of solar light by the solar interface evaporation device.

On the other hand, the coupling of copper sulfide and reduced graphene oxide not only changes the utilization rate of sunlight by the solar interfacial evaporation device, but also increases the surface area and porosity of the solar interfacial evaporation device. The enlarged surface area can increase the area of the gas-water evaporation interface, and the increased porosity can accelerate the transport of seawater and the escape of water vapor by the solar interfacial evaporation device. The heat generated can be effectively transferred to seawater, which helps to increase the water evaporation rate. In addition, the flower cluster structure composed of copper sulfide nanosheets also allows the incident light to be scattered and absorbed multiple times on the photothermal conversion material, giving the photothermal conversion material an excellent photothermal effect.

Mxene nanosheets have the characteristics of strong visible light absorption capacity, high photothermal conversion efficiency, wide light absorption range, etc., and their photothermal conversion efficiency is close to 100%, but due to their inherent high surface energy and interfacial van der Waals effect, they are prone to agglomeration. The present invention etches titanium aluminum carbide to obtain a few-layer Mxene nanosheets by using lithium fluoride and hydrochloric acid to generate hydrogen fluoride in situ, and adds MXene nanosheets with strong light absorption to the precursor mixture. The hydroxyl functional groups rich on the surface of the Mxene nanosheets can produce hydrogen bonds with the hydroxyl functional groups of nanocellulose in the precursor mixture. After directional freeze drying, a porous, hydrophilic aerogel matrix with a vertical pore structure is formed, and the MXene nanosheets are attached to the surface of the aerogel matrix and the inner wall of the pores, which can effectively prevent the Mxene nanosheets from agglomerating. At the same time, by adding MXene nanosheets, the light absorption capacity and water absorption capacity of the solar interface evaporation device can be significantly enhanced. This is because, on the one hand, during the evaporation of seawater, when sunlight irradiates the solar interface evaporation device, part of the sunlight is absorbed by the MXene nanosheets on the surface of the solar interface evaporation device, and the remaining sunlight enters the pores of the solar interface evaporation device, and after multiple reflections, it is absorbed again by the MXene nanosheets on the inner wall of the pores, and finally converted into heat energy and heats the water to produce water vapor. The porous structure of the aerogel matrix itself and the light absorption capacity of the MXene nanosheets enhance the absorption effect of the solar interface evaporation device on sunlight. On the other hand, the excessive hydrophilic functional groups on the surface of the MXene nanosheets further improve the hydrophilicity of the aerogel matrix surface and the inner wall of the pores, promoting the rapid movement and transmission of seawater on its hydrophilic surface. In addition, it can bind to water molecules through hydrogen bonds to activate them, reduce the evaporation enthalpy of seawater, thereby accelerating the evaporation rate of seawater, which is beneficial to solar desalination. On the other hand, the present invention selects graphene oxide as a common building unit to assist in the assembly of Mxene nanosheets. The strong interaction between the Mxene nanosheets and the graphene oxide can bond the Mxene nanosheets to form continuous sheets. The two are synergistically dispersed to reduce the re-accumulation of the Mxene nanosheets in the aerogel matrix, thereby maximizing the specific surface area of the Mxene nanosheets, so that the freeze-dried aerogel matrix exhibits excellent mechanical strength; in addition, due to the intrinsic hydrophilicity of the Mxene nanosheets and the slightly reduced reduced graphene oxide, the aerogel matrix exhibits hydrophilicity as a whole, combined with the stable vertical pore structure, which significantly improves the water absorption capacity of the solar interface evaporation device.

In order to further improve the light absorption capacity of the Mxene nanosheets and prevent the Mxene nanosheets from falling off from the surface or pores of the aerogel matrix, the present invention uses polyethyleneimine and dopamine to jointly modify the Mxene nanosheets before adding the Mxene nanosheets to the precursor mixture, so as to form a polyethyleneimine/polydopamine cross-linked network on the surface of the Mxene nanosheets. The synergistic effect of polyethyleneimine and polydopamine is reflected in: on the one hand, polyethyleneimine and polydopamine give the Mxene nanosheets more excellent hydrophilicity, further improve the wetting ability of the solar interface evaporation device for seawater, and promote the diffusion and transmission of seawater in the solar interface evaporation device and the surface and pores. At the same time, after loading polydopamine, the surface of the Mxene nanosheet presents a rough wrinkled morphology, which helps to improve the Mxene On the other hand, since polydopamine contains multiple hydroxyl and amino functional groups, the MXene nanosheets can be more firmly adsorbed on the surface of the aerogel matrix and the inner wall of the pores under the interaction of electrostatic adsorption and hydrogen bonds, which enhances the loading strength of the modified MXene nanosheets on the aerogel matrix and prevents the modified MXene nanosheets from falling off from the pores during long-term use of the solar interfacial evaporation device; on the other hand, through the Shiff base and Michael addition reaction, an extremely thin polyethyleneimine/polydopamine physical barrier film can be assembled on the surface of the MXene nanosheets to prevent oxygen from continuously diffusing inward into the MXene lattice, thereby effectively inhibiting the spontaneous oxidation and shedding of the MXene nanosheets, and improving the environmental stability and service life of the solar interfacial evaporation device.

The present invention uses quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate as the matrix components of the hydrogel, forms a hydrogel intermediate with a stable skeleton structure under the combined action of glutaraldehyde crosslinking and hydrogen bonding, and then obtains a composite hydrogel through a freeze-thaw cycle process. There are two different crosslinked network structures in the composite hydrogel:

The first is a chemically cross-linked network structure with excellent mechanical strength formed by oxidized sodium alginate and quaternized chitosan through Schiff base chemical cross-linking. Oxidized sodium alginate contains a large number of functional groups such as hydroxyl and carboxyl, which can be cross-linked with the hydroxyl functional groups on modified polyvinyl alcohol and nanocellulose through hydrogen bonding. In addition, the modified MXene nanosheets obtained after etching, stripping and modification also contain a large number of hydrophilic functional groups and fluoride anions, which can make the modified MXene nanosheets uniformly distributed in the chemically cross-linked network structure formed by oxidized sodium alginate and quaternized chitosan. The present invention adopts 2,3-epoxypropyltrimethyl chloride Chitosan is quaternized by ammonium. Unmodified chitosan has a very high crystallinity due to the presence of a large number of hydrogen bonds within and between molecules, making it difficult for solvents to penetrate and having poor solubility. The present invention introduces 2,3-epoxypropyltrimethylammonium chloride with large steric hindrance and strong hydration ability into the molecular structure of chitosan, and then introduces a quaternary ammonium salt functional group with a permanent positive charge on the skeleton of chitosan. Most of the hydrogen bonds in the chitosan molecules are destroyed, while the remaining hydrogen bonds and newly formed amide hydrogen bonds are weak, thereby effectively destroying the hydrogen bonds between the amino group and the hydroxyl group, making it difficult to form a new crystalline structure, so that the chitosan derivative is in a more amorphous state, the crystallinity is reduced, and the water solubility is increased.

The second is a physical cross-linked network structure formed by polyvinyl alcohol and propylene glycol through hydrogen bonding. The physical cross-linked network structure is interpenetrated in the chemical cross-linked network structure. The physical cross-linked network structure can make water molecules evaporate in the form of clusters to reduce the evaporation enthalpy of water. In the composite hydrogel, there are a large number of hydroxyl groups on the modified polyvinyl alcohol molecular chain, which can combine with water molecules through hydrogen bonding and electrostatic effects, thereby activating the water molecules and generating a large number of weakly bound water molecules, which promotes the evaporation of water and improves the utilization rate of sunlight. In addition, the hydroxyl functional groups on the modified polyvinyl alcohol can also be tightly cross-linked with the amino functional groups of polydopamine through hydrogen bonding, so that the modified Mxene nanosheets modified by polydopamine can be firmly attached to the aerogel matrix.

The present invention adds nanocellulose to the aerogel matrix, and by virtue of the mechanical enhancement performance, low thermal conductivity and super hydrophilicity of nanocellulose, the water transmission capacity, thermal management capacity and mechanical strength of the aerogel matrix can be further enhanced. On the one hand, nanocellulose has abundant hydrophilic functional groups such as hydroxyl groups, so it can continuously transport water to the surface of the solar interface evaporation device through its excellent hydrophilicity, thereby improving the transport capacity of the solar interface evaporation device for seawater. On the other hand, nanocellulose with a fiber filament structure with a high aspect ratio forms a three-dimensional network structure in the precursor mixture through physical cross-entanglement and hydrogen bonding, and constructs a three-dimensional porous structure in the aerogel matrix after freeze-drying, which not only provides abundant transmission channels for the escape of water vapor, but also effectively improves the mechanical strength of the aerogel matrix. In addition, in the aerogel matrix, the excellent light absorption and photothermal conversion properties of the modified Mxene nanosheets ensure that the aerogel matrix can absorb sunlight and convert it into heat for heating water. With the help of the hydrogen bonding between the hydroxyl groups on the modified Mxene nanosheets and the hydroxyl groups on nanocellulose and the three-dimensional network structure of nanocellulose itself, the stacking phenomenon of Mxene nanosheets in the gel precursor solution can be effectively alleviated, thereby avoiding the decrease in the light absorption performance of the aerogel matrix.

The present invention introduces aniline monomers into the composite hydrogel. Under the combined action of the modified Mxene nanosheets and ammonium persulfate, the aniline monomers undergo nucleation grafting in the three-dimensional network structure of the composite hydrogel to self-polymerize on the surface of the modified Mxene nanosheets to form short-chain polyaniline nanofibers. The reaction mechanism of the whole process is as follows:

The surface of the modified Mxene nanosheets contains a large number of -F, -O and -OH functional groups. In the weakly acidic environment formed by ammonium persulfate, the -O and -OH functional groups on the Mxene nanosheets can oxidize the aniline monomer to form aniline cationic radicals or neutral radicals. In this process, two aniline cationic radicals are polymerized in a head-to-tail manner to form aniline dimers. At the same time, after the initial polymerization reaction is completed, the aniline dimer can continue to polymerize by electrophilic substitution of the hydrogen atoms of the benzene ring in the oxidation product of aniline to form aniline dimers. Since the oxidation potential of the generated aniline dimer is much lower than that of the aniline monomer, the aniline dimer can be rapidly oxidized by subsequent oxidation or deprotonation during the formation process and react with other free aniline monomers to form short-chain polyaniline nanofibers.

When the composite hydrogel is immersed in the aniline monomer solution, the aniline monomer will self-polymerize on the surface of the modified MXene nanosheet according to the above reaction process, and form nuclei and grafted short-chain polyaniline nanofibers on the surface of the modified MXene nanosheet. The grafted short-chain polyaniline nanofibers will also be tightly bound to the reduced graphene oxide in the photothermal conversion material through hydrogen bonds, π-π conjugated interactions and van der Waals forces. Under the action of the "molecular bridge" formed by the short-chain polyaniline nanofibers, the modified MXene nanosheets are connected to the photothermal conversion material, and finally a modified composite hydrogel with a stable structure is formed. In addition, the short-chain polyaniline nanofibers formed by the self-polymerization of the aniline monomer can also be inserted into the lamellae of the reduced graphene oxide, thereby increasing the interlamellar spacing of the reduced graphene oxide and effectively inhibiting the agglomeration problem of the reduced graphene oxide.

Due to the disordered growth of ice crystals, the aerogel matrix prepared by the traditional freezing method mostly shows a disordered pore structure, not only the internal pores are unevenly distributed, but also the open and closed pore structures coexist, and the existence of the closed pore structure affects the water transport and water vapor dissipation process. The present invention adopts directional freeze drying to prepare an aerogel matrix with a vertical pore structure. The principle is to control the growth direction of ice crystals in the modified composite hydrogel by applying a temperature gradient to the modified composite hydrogel. Under the action of the temperature gradient, the ice crystals grow directionally from the low temperature end to the high temperature end along the vertical direction, and then the ice crystals are sublimated after freeze drying in the freeze dryer. The final pores directly replicate the structure of the ice crystals, and a vertically arranged porous structure is formed in the final aerogel matrix.

The advantages of the axially ordered and regularly arranged pore channels prepared by the present invention are:

(1) A directional pore structure is formed inside the aerogel matrix by using a directional freezing process, which shortens the distance of water transport, reduces the resistance of water transport, and makes the water vapor escape more fully, greatly improving the simulated seawater climbing distance and water evaporation rate of the solar interface evaporation device, while also effectively preventing the formation of a closed-pore structure inside the aerogel matrix;

(2) When sunlight enters the vertical channel, it can be refracted multiple times between the inner walls of the vertical channel, which helps to improve the solar interface evaporation device's absorption rate of sunlight and achieve efficient absorption of solar energy;

(3) This vertically arranged macroporous channel can quickly replenish the water evaporated from the surface of the solar interface evaporation device, so that the solar interface evaporation device can maintain high efficiency for a long time, thereby improving the solar interface evaporation device's ability to absorb sunlight and water evaporation performance;

(4) With the directional growth of ice crystals, photothermal conversion materials and modified Mxene nanosheets can be deposited on the pore walls of the aerogel matrix, which is conducive to the full exposure of photothermal conversion materials and modified Mxene nanosheets to achieve maximum pore utilization, thereby improving the photothermal conversion efficiency of solar interfacial evaporation devices.

The invention adopts a chemical oxidation polymerization method to load polypyrrole on the surface and inside of an aerogel matrix, and adopts FeCl ₃ as an oxidant to oxidize pyrrole monomers to synthesize polypyrrole. When the polymerization reaction starts, under the action of FeCl ₃ , the pyrrole monomers are oxidized to generate some cationic free radicals to undergo protonation reaction, and these chemically active cationic free radicals are combined in pairs to generate a bipyrrole structure, and the bipyrrole structure is further oxidized and continues to couple with other oxidized pyrrole monomers, and the oxidation and coupling process continues until a polypyrrole molecular chain is formed, and finally a black water-insoluble polypyrrole is obtained.

Since polypyrrole itself is black, it can be used as a light absorption site and spontaneously absorbs most of the light when irradiated with light, significantly improving the light capture ability of the solar interface evaporation device; at the same time, the vertical channel structure inside the aerogel matrix causes sunlight to be repeatedly refracted and scattered inside the aerogel matrix, promoting light capture, resulting in the final prepared solar interface evaporation device having almost no light transmission in the wavelength range of 300~2500nm, achieving full-spectrum wide absorption with an absorption rate of about 98%. The introduced photothermal conversion materials and modified Mxene nanosheets can quickly convert solar energy into thermal energy to achieve effective energy conversion. The synergistic effect of these factors is conducive to accelerating the water interface evaporation of the solar interface evaporation device.

There is also a synergistic effect between polypyrrole and modified Mxene nanosheets, which is mainly reflected in:

On the one hand, after HCl-LiF etching, the surface of the modified MXene nanosheets exposes abundant fluorine-containing and oxygen-containing functional groups. The N-H functional groups in the polypyrrole ring and the fluorine-containing and oxygen-containing functional groups on the surface of the modified MXene nanosheets can form a stable physical adsorption structure between the polypyrrole and the modified MXene nanosheets, which is beneficial to the composite of the modified MXene nanosheets and the polypyrrole, so that the polypyrrole molecular chains can be evenly distributed on the MXene nanosheets and inserted into the edges and defective parts of the MXene nanosheets. The insertion of the polypyrrole molecular chains can effectively prevent the oxidative degradation reaction of the defective parts of the modified MXene nanosheets; at the same time, the polypyrrole is embedded in the layered structure of the modified MXene nanosheets, which can increase the interlayer spacing of the modified MXene nanosheets and play a spatial barrier role, which solves the problem of sheet stacking of the modified MXene nanosheets to a certain extent; in addition, the polypyrrole particles coated on the surface of the modified MXene nanosheets can protect the modified MXene nanosheets from oxidation. The modified MXene nanosheets were passivated after being compounded with polypyrrole, and the structural stability of the modified MXene nanosheets was significantly improved. The structural stability of polypyrrole after being doped with the modified MXene nanosheets was also improved.

On the other hand, in the traditional polypyrrole polymerization reaction, an initiator is added, while in the polymerization process of the present invention, no other initiator is used to participate in the reaction, and only a simple _FeCl3 oxidant is used to polymerize the pyrrole monomer. This is because the modified MXene nanosheets themselves are acidic, and under acidic conditions, a protonation reaction will occur at the C-3 position of the pyrrole ring. After the pyrrole molecules are protonated, they will continue to protonate other molecules to form a bipyrrole structure until a long chain of polypyrrole molecules is generated.

As a preferred technical solution of the present invention, in step (I), the mass fraction of graphene oxide in the graphene oxide dispersion is 10-20wt%, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of graphene oxide to L-cysteine in the graphene oxide dispersion is 1:(15~25), for example, it can be 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24 or 1:25, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the concentration of cupric chloride in the cupric chloride solution is 1-1.2 mol/L, for example, it can be 1.0 mol/L, 1.02 mol/L, 1.04 mol/L, 1.06 mol/L, 1.08 mol/L, 1.1 mol/L, 1.12 mol/L, 1.14 mol/L, 1.16 mol/L, 1.18 mol/L or 1.2 mol/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of L-cysteine in the reaction solution to copper chloride in the copper chloride solution is (3-5):1, for example, 3.0:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4.0:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1 or 5.0:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional instances, the heating temperature of the precursor solution is 140-160°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C or 160°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the heating time of the precursor solution is 10 to 15 hours, for example, it can be 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours or 15 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (II), the concentration of the hydrochloric acid solution is 3-5 mol/L, for example, it can be 3.0 mol/L, 3.2 mol/L, 3.4 mol/L, 3.6 mol/L, 3.8 mol/L, 4.0 mol/L, 4.2 mol/L, 4.4 mol/L, 4.6 mol/L, 4.8 mol/L or 5.0 mol/L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional examples, the mixing ratio of lithium fluoride and hydrochloric acid solution is 1g:(15~25)mL, for example, it can be 1g:15mL, 1g:16mL, 1g:17mL, 1g:18mL, 1g:19mL, 1g:20mL, 1g:21mL, 1g:22mL, 1g:23mL, 1g:24mL or 1g:25mL, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mixing ratio of the etching solution and the titanium aluminum carbide powder is 1L:(30~40)g, for example, it can be 1L:30g, 1L:31g, 1L:32g, 1L:33g, 1L:34g, 1L:35g, 1L:36g, 1L:37g, 1L:38g, 1L:39g or 1L:40g, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the temperature of the water bath heating when the etching solution and the titanium aluminum carbide powder are mixed is 30~40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the water bath heating time when the etching solution and the titanium aluminum carbide powder are mixed is 12 to 24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the concentration of the Mxene nanosheets in the Mxene dispersion is 3 to 5 g/L, for example, 3.0 g/L, 3.2 g/L, 3.4 g/L, 3.6 g/L, 3.8 g/L, 4.0 g/L, 4.2 g/L, 4.4 g/L, 4.6 g/L, 4.8 g/L or 5.0 g/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of the Mxene nanosheets to the polyethyleneimine in the Mxene dispersion is 1:(0.6~0.8), for example, it can be 1:0.6, 1:0.62, 1:0.64, 1:0.66, 1:0.68, 1:0.7, 1:0.72, 1:0.74, 1:0.76, 1:0.78 or 1:0.8, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional embodiments, the heating temperature of the amino-modified heated oscillation is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the shaking speed of the amino-modified heated oscillating table is 150~250r/min, for example, it can be 150r/min, 160r/min, 170r/min, 180r/min, 180r/min, 200r/min, 210r/min, 220r/min, 230r/min, 240r/min or 250r/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the modification time of the heating oscillation for the amino modification is 1 to 2 hours, for example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the dopamine solution consists of dopamine and Tris-HCl buffer solution.

In some optional embodiments, the pH value of the Tris-HCl buffer solution is 8-9, for example, it can be 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9.0, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the concentration of dopamine in the dopamine solution is 0.5~1.5 g/L, for example, it can be 0.5 g/L, 0.6 g/L, 0.7 g/L, 0.8 g/L, 0.9 g/L, 1.0 g/L, 1.1 g/L, 1.2 g/L, 1.3 g/L, 1.4 g/L or 1.5 g/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Polydopamine can significantly promote the exfoliation of MXene nanosheets, but when the concentration of dopamine solution exceeds 1.5 g/L, the exfoliation effect of MXene nanosheets becomes worse. This is because the excess polydopamine nanoparticles produce a stronger interaction with the functional groups on the surface of MXene nanosheets, thereby slightly reducing the interlayer spacing of MXene nanosheets.

In some optional examples, the volume ratio of the Mxene dispersion to the dopamine solution is (10-12):1, for example, it can be 10:1, 10.2:1, 10.4:1, 10.6:1, 10.8:1, 11:1, 11.2:1, 11.4:1, 11.6:1, 11.8:1 or 12:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the Mxene dispersion and the dopamine solution are mixed and oscillated in a shaker for 12 to 24 hours, for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (III), the mass fraction of acetic acid in the acetic acid aqueous solution is 2-3wt%, for example, it can be 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt% or 3.0wt%, but it is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional examples, the mixing ratio of chitosan and acetic acid aqueous solution is 1g:(40~60)mL, for example, it can be 1g:40mL, 1g:42mL, 1g:44mL, 1g:46mL, 1g:48mL, 1g:50mL, 1g:52mL, 1g:54mL, 1g:56mL, 1g:58mL or 1g:60mL, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional embodiments, the heating temperature when the chitosan is mixed with the acetic acid aqueous solution is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional embodiments, the stirring time when the chitosan and the acetic acid aqueous solution are mixed is 2 to 3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride in the chitosan solution is 1:(1.6~1.8), for example, it can be 1:1.6, 1:1.62, 1:1.64, 1:1.66, 1:1.68, 1:1.7, 1:1.72, 1:1.74, 1:1.76, 1:1.78 or 1:1.8, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the heating temperature of the chitosan solution and 2,3-epoxypropyltrimethylammonium chloride during the quaternization modification process is 75-85°C, for example, it can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the stirring time of the chitosan solution and 2,3-epoxypropyltrimethylammonium chloride during the quaternization modification process is 10 to 12 hours, for example, it can be 10 hours, 10.2 hours, 10.4 hours, 10.6 hours, 10.8 hours, 11 hours, 11.2 hours, 11.4 hours, 11.6 hours, 11.8 hours or 12 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of the polyvinyl alcohol, glycerol and deionized water is 1:(2.5~3.5):(1.8~2.2), for example, it can be 1:2.5:1.8, 1:2.6:1.85, 1:2.7:1.9, 1:2.8:1.95, 1:2.9:2, 1:3.0:2.05, 1:3.1:2.1, 1:3.2:2.15, 1:3.3:2.2, 1:3.4:2.2 or 1:3.5:2.2, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the reaction temperature of the heated reflux reaction of the reaction precursor solution is 100-120°C, for example, it can be 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C or 120°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the reaction time of the heating reflux reaction of the reaction precursor solution is 1 to 2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass fraction of sodium alginate in the sodium alginate solution is 3-5wt%, for example, 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt%, 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt% or 5.0wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the mass ratio of sodium alginate to sodium periodate in the sodium alginate solution is (2-3):1, for example, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the stirring time of the sodium alginate solution and sodium periodate during the oxidation reaction is 3 to 5 hours, for example, it can be 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5.0 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (IV), the mass ratio of the quaternized chitosan, the modified polyvinyl alcohol, the oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:(3-5):(0.5-0.8):(0.6-0.7), for example, it can be 1:3:0.5:0.6, 1:3.2:0.55:0.61, 1:3.4:0.6:0.62, 1 :3.6:0.65:0.63, 1:3.8:0.7:0.64, 1:4:0.75:0.65, 1:4.2:0.8:0.66, 1:4.4:0.7:0.67, 1:4.6:0.75:0.68, 1:4.8:0.8:0.69 or 1:5:0.85:0.7, but are not limited to the listed values, other values not listed within the numerical range are also applicable.

The present invention adds nanocellulose to the precursor mixture, increases the interlayer spacing of the modified Mxene nanosheets, reduces the stacking phenomenon of the modified Mxene nanosheets, improves the light absorption performance of the aerogel matrix, and at the same time, the increase in the interlayer spacing of the modified Mxene nanosheets also blocks the conduction and dissipation of heat to a certain extent. However, when the amount of nanocellulose added is lower than the lower limit of the range defined by the present invention, the interlayer spacing of the modified Mxene nanosheets will be reduced, and the modified Mxene nanosheets will stack, thereby causing the surface temperature of the solar interface evaporation device to drop. When the amount of nanocellulose added is higher than the upper limit of the range defined by the present invention, the viscosity of the precursor mixture will be too large, affecting the dispersion uniformity of the photothermal conversion material and the Mxene nanosheets in the precursor mixture.

In some optional examples, the mass fraction of the nanocellulose solution is 0.5~1.5wt%, for example, it can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or 1.5wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets is 1:(0.01-0.05):(0.005-0.01), for example, 1:0.01:0.005, 1:0.015:0.0055, 1:0.02:0.0 06, 1: 0.025: 0.0065, 1: 0.03: 0.007, 1: 0.035: 0.0075, 1: 0.04: 0.008, 1: 0.045: 0.0085, 1: 0.05: 0.009, 1: 0.05: 0.0095, 1: 0.05: 0.01, but are not limited to the listed values, other values not listed within the numerical range are also applicable.

The water absorption performance, evaporation performance and photothermal conversion performance of the solar interfacial evaporation device show a trend of first increasing and then decreasing with the increase of the amount of modified MXene nanosheets added. This is because the modified MXene nanosheets have excellent photothermal conversion efficiency. The addition of modified MXene nanosheets can significantly enhance the light absorption capacity of the solar interfacial evaporation device. At the same time, the excessive hydrophilic functional groups on the surface of the MXene nanosheets further improve the hydrophilicity of the aerogel matrix surface and the inner wall of the pores, and promote the rapid movement and transmission of seawater on its hydrophilic surface. Therefore, with the increase of the amount of MXene nanosheets added, the water absorption performance, evaporation performance and photothermal conversion performance of the solar interfacial evaporation device are significantly improved. However, when the amount of modified Mxene nanosheets added exceeds the upper limit of the range defined in the present invention, the physical crosslinking of the modified Mxene nanosheets and sodium alginate forms a denser network structure, resulting in a decrease in the pore size of the pores in the aerogel matrix finally formed, affecting the water transport and water vapor escape inside the aerogel matrix, and reducing the water absorption and evaporation performance of the solar interface evaporation device; in addition, when the modified Mxene nanosheets are added in excess, the modified Mxene nanosheets agglomerate, resulting in a decrease in the interlamellar spacing of the modified Mxene nanosheets, resulting in a decrease in the aerogel matrix's ability to absorb sunlight, and an increase in the thermal conductivity of the aerogel matrix, which in turn causes the heat generated by photothermal conversion to be rapidly conducted and dissipated, making it difficult to be used in time to heat water.

The water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device show a trend of first increasing and then decreasing with the increase of the amount of photothermal conversion material added. This is because the photothermal conversion material can effectively absorb sunlight in the visible light and near-infrared radiation regions and convert it into heat, thereby evaporating seawater into water vapor. As the amount of photothermal conversion material added gradually increases, the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device gradually improve. When the amount of photothermal conversion material added exceeds the upper limit of the range specified by the present invention, the photothermal conversion material will agglomerate, thereby affecting the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device.

In some optional examples, the ultrasonic power of the ultrasonic dispersion of the precursor mixture, the photothermal conversion material and the modified Mxene nanosheets is 400-500 W, for example, 400 W, 410 W, 420 W, 430 W, 440 W, 450 W, 460 W, 470 W, 480 W, 490 W or 500 W, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the ultrasonic dispersion time of the precursor mixture, the photothermal conversion material and the modified Mxene nanosheets is 1 to 2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (V), the concentration of the hydrochloric acid solution is 1-2 mol/L, for example, it can be 1.0 mol/L, 1.1 mol/L, 1.2 mol/L, 1.3 mol/L, 1.4 mol/L, 1.5 mol/L, 1.6 mol/L, 1.7 mol/L, 1.8 mol/L, 1.9 mol/L or 2.0 mol/L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional examples, the mass fraction of glutaraldehyde in the glutaraldehyde acid solution is 2-3wt%, for example, 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt% or 3.0wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the ratio of the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the gel precursor solution to the mass of glutaraldehyde in the glutaraldehyde acid solution is 1:(10-20), for example, it can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, after all the glutaraldehyde solution is added dropwise, the mixture is stirred for 0.5 to 1.5 hours to cause a cross-linking reaction, for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours or 1.5 hours; and then the mixture is allowed to stand for 3 to 5 hours to complete gelation, for example, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5.0 hours, but the mixture is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional examples, the freezing temperature of the hydrogel intermediate is -20~-30°C, for example, it can be -20°C, -21°C, -22°C, -23°C, -24°C, -25°C, -26°C, -27°C, -28°C, -29°C or -30°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the freezing time of the hydrogel intermediate is 3 to 5 hours, for example, it can be 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5.0 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional embodiments, the thawing temperature of the hydrogel intermediate is 30-40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the thawing time of the hydrogel intermediate is 3 to 5 hours, for example, it can be 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5.0 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (VI), the concentration of the aniline monomer in the aniline monomer solution is 1.5-2.5 g/L, for example, it can be 1.5 g/L, 1.6 g/L, 1.7 g/L, 1.8 g/L, 1.9 g/L, 2.0 g/L, 2.1 g/L, 2.2 g/L, 2.3 g/L, 2.4 g/L or 2.5 g/L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

During the in-situ growth of short-chain polyaniline nanofibers, the concentration of aniline monomer in the aniline monomer solution will have a significant effect on the nanomorphology of short-chain polyaniline. When the concentration of aniline monomer in the aniline monomer solution is lower than 1.5 g/L, the concentration of aniline monomer is too low to trigger the grafting process, and only granular clusters are formed, and short-chain polyaniline nanofibers cannot be formed. When the concentration of aniline monomer in the aniline monomer solution is in the range of 1.5~2.5 g/L, the short-chain polyaniline nanofibers grown on the surface of the modified MXene nanosheets are relatively regular and have a large number density. When the concentration of aniline monomer in the aniline monomer solution exceeds 2.5 g/L, short-chain polyaniline nanofibers cannot be formed on the surface of the modified MXene nanosheets. This is because the concentration of aniline monomer is too high, resulting in nucleation and grafting growth of aniline monomer in the solution, so that polyaniline is generated and precipitated in the solution in a large amount in the form of free state, and cannot be directly grafted and grown on the surface of the modified MXene nanosheets.

In some optional examples, the mass ratio of the aniline monomer in the aniline monomer solution to the ammonium persulfate in the ammonium persulfate solution is 1:(2-3), for example, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 or 1:3.0, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, after all the ammonium persulfate solution is dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 0.5 to 1.5 hours, for example, it can be 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours or 1.5 hours; and then allowed to stand for 2 to 3 hours to complete the polymerization reaction to generate polyaniline, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but it is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional instances, the temperature of the cold plate is -50~-60°C, for example, it can be -50°C, -51°C, -52°C, -53°C, -54°C, -55°C, -56°C, -57°C, -58°C, -59°C or -60°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the modified composite hydrogel is placed on a cold plate for 30 to 50 minutes, for example, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes, 40 minutes, 42 minutes, 44 minutes, 46 minutes, 48 minutes or 50 minutes, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the freeze-drying temperature of the modified composite hydrogel in the freeze dryer is -70~-80°C, for example, it can be -70°C, -71°C, -72°C, -73°C, -74°C, -75°C, -76°C, -77°C, -78°C, -79°C or -80°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the freeze-drying time of the modified composite hydrogel in the freeze dryer is 12 to 24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

As a preferred technical solution of the present invention, in step (VII), the concentration of the hydrochloric acid solution is 0.5-1.5 mol/L, for example, it can be 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1.0 mol/L, 1.1 mol/L, 1.2 mol/L, 1.3 mol/L, 1.4 mol/L or 1.5 mol/L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In some optional examples, the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:(10-20), for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present invention specifically limits the volume ratio of pyrrole monomer to hydrochloric acid solution to 1: (10-20), and the volume ratio of pyrrole monomer to hydrochloric acid solution will directly affect the amount of polypyrrole generated. Too low or too high a polypyrrole generation will affect the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. If the polypyrrole generation is too low, the hydrophilicity and photothermal conversion capacity are insufficient, and the solar interface evaporation device is difficult to absorb water and the internal water is difficult to evaporate, resulting in a decrease in the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device; if the polypyrrole generation is too high, it will block part of the pores inside the solar interface evaporation device, affect the transmission of water and the escape of water vapor, resulting in a decrease in the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. Only when the volume ratio of pyrrole monomer to hydrochloric acid solution is within the range of 1: (10-20), the amount of polypyrrole generated is moderate, which can ensure that the solar interface evaporation device has sufficient photothermal conversion performance and will not block the pore structure inside the solar interface evaporation device.

In some optional examples, the speed of magnetic stirring when the aerogel matrix is immersed in the pyrrole monomer solution is 700-800 r/min, for example, it can be 700 r/min, 710 r/min, 720 r/min, 730 r/min, 740 r/min, 750 r/min, 760 r/min, 770 r/min, 780 r/min, 790 r/min or 800 r/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the magnetic stirring time when the aerogel matrix is immersed in the pyrrole monomer solution is 1 to 2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the molar ratio of the pyrrole monomer in the pyrrole monomer solution to the ferric chloride in the ferric chloride solution is 1:(1.5~2.5), for example, it can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the concentration of ferric chloride in the ferric chloride solution is 30-40 g/L, for example, 30 g/L, 31 g/L, 32 g/L, 33 g/L, 34 g/L, 34 g/L, 36 g/L, 37 g/L, 38 g/L, 39 g/L or 40 g/L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

In some optional examples, the ice water bath temperature of the pyrrole monomer solution and the ferric chloride solution is 0-10°C, for example, it can be 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present invention selects to carry out the polymerization reaction of pyrrole monomer in a low temperature environment, because pyrrole monomer will quickly polymerize to form polypyrrole in a high temperature environment, and most of the polypyrrole will not be loaded on the aerogel matrix. In addition, there are many defects in the polypyrrole conjugated chain generated by polymerization on the aerogel matrix, resulting in poor light-to-heat conversion performance. The reaction rate of the polymerization reaction system under low temperature conditions is relatively slow, and the pyrrole monomer can be fully polymerized on the surface of the aerogel matrix, and the defects on the long molecular chain of polypyrrole can be reduced.

In some optional examples, the rotation speed of the magnetic stirring of the pyrrole monomer solution and the ferric chloride solution is 300-400 r/min, for example, it can be 300 r/min, 310 r/min, 320 r/min, 330 r/min, 340 r/min, 350 r/min, 360 r/min, 370 r/min, 380 r/min, 390 r/min or 400 r/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the magnetic stirring time of the pyrrole monomer solution and the ferric chloride solution is 1 to 2 hours, for example, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In some optional examples, the liquid nitrogen freeze-drying time is 10 to 20 minutes, for example, it can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In a second aspect, the present invention provides a nanocellulose-based solar interface evaporation device prepared by the preparation method described in the first aspect.

In a third aspect, the present invention provides a use of the nanocellulose-based solar interface evaporation device described in the second aspect, wherein the nanocellulose-based solar interface evaporation device is used for seawater desalination.

Compared with the prior art, the present invention has the following beneficial effects:

The invention uses quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and nanocellulose solution as gel precursor solution, adds photothermal conversion material composed of graphene oxide and copper sulfide and modified Mxene nanosheets modified by polyethyleneimine and polydopamine into the gel precursor solution, and constructs a composite hydrogel with a good skeleton structure through hydrogen bond crosslinking and freeze-thaw cycle under the action of glutaraldehyde crosslinking agent; then, chemical in-situ polymerization is used, and ammonium persulfate is used as an oxidant to induce aniline monomer to grow in-situ inside the composite hydrogel to generate polyaniline nanofibers; an aerogel matrix with vertically arranged macroporous channels is obtained through directional freeze drying; finally, pyrrole in-situ polymerization reaction is performed on the surface of the aerogel matrix to generate polypyrrole; the polypyrrole, as a light absorption site, significantly improves the light capture ability of a solar interface evaporation device, helps to achieve wide absorption of the solar interface evaporation device in the full spectrum range, and improves the utilization rate of sunlight by the solar interface evaporation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a transmission electron microscope image of the photothermal conversion material prepared in Example 1 of the present invention at a low magnification;

FIG2 is a transmission electron microscope image of the photothermal conversion material prepared in Example 1 of the present invention at a high magnification;

FIG3 is an infrared spectrum of graphene oxide, reduced graphene oxide and the photothermal conversion material prepared in Example 1 of the present invention;

FIG4 is a scanning electron microscope image of MXene nanosheets prepared in Example 1 of the present invention;

FIG5 is a transmission electron microscope image of MXene nanosheets prepared in Example 1 of the present invention;

FIG6 is a scanning electron microscope image of the internal structure of the aerogel matrix prepared in Example 1 of the present invention;

FIG7 is a scanning electron microscope image of the solar interface evaporation device prepared in Example 1 of the present invention at a low magnification;

FIG8 is a scanning electron microscope image of the solar interface evaporation device prepared in Example 1 of the present invention at a high magnification;

FIG9 is a planar temperature distribution diagram of seawater and the solar interface evaporation device prepared in Example 1 of the present invention under a light intensity of 1 kW/m;

FIG10 is a diagram showing the surface water contact angle of the solar interface evaporation device prepared in Example 1 of the present invention;

FIG. 11 is a schematic diagram of the structure of a seawater evaporation experimental device used in the evaporation performance test of the solar interface evaporation device prepared in Examples 1-15 of the present invention.

DETAILED DESCRIPTION

The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

Example 1

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, and the preparation method specifically comprises the following steps:

(1) Dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a mass fraction of 10 wt% after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion, the mass ratio of graphene oxide to L-cysteine being 1:15, and mixing and stirring until L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution with a concentration of 1 mol/L to the reaction solution, the mass ratio of L-cysteine to copper chloride being 3:1, and mixing uniformly to obtain a precursor solution, transferring the precursor solution to a reactor and heating it at 140° C. for 15 h, so that L-cysteine reacts with copper chloride to generate copper sulfide, and at the same time, graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, filtering, washing and drying the reaction product to obtain a photothermal conversion material composed of graphene oxide and copper sulfide;

(2) Add lithium fluoride to a hydrochloric acid solution with a concentration of 3 mol/L, the mixing ratio of lithium fluoride to hydrochloric acid solution is 1 g:25 mL, and the etching solution is obtained after being evenly mixed. Titanium aluminum carbide powder is added to the etching solution, and the mixing ratio of the etching solution to titanium aluminum carbide powder is 1 L:30 g. After magnetic stirring and heating in a water bath at 30°C for 24 hours, a suspension is obtained. The suspension is washed and centrifuged with deionized water in sequence. After repeating the washing and centrifugation operations three times, the precipitate is dispersed in deionized water, and the supernatant is dried after standing to obtain Mxene nanosheets;

The Mxene nanosheets were dispersed in deionized water to form a Mxene dispersion with a concentration of 3 g/L, and the Mxene dispersion was transferred to a shaker, polyethyleneimine was added to the Mxene dispersion, the mass ratio of the Mxene nanosheets to the polyethyleneimine was 1:0.6, and the Mxene dispersion was heated and shaken in a shaker for 1 hour for amino modification, the heating temperature was 50°C, and the shaking speed was 150 r/min; then, a dopamine solution with a concentration of 0.5 g/L was added to the Mxene dispersion at room temperature, the volume ratio of the Mxene dispersion to the dopamine solution was 10:1, wherein the pH value of the Tris-HCl buffer solution in the dopamine solution was 8, and the dopamine was mixed and shaken in a shaker for 12 hours to allow the dopamine to undergo in-situ oxidation self-polymerization to form polydopamine, and finally the modified Mxene nanosheets were obtained after filtration, washing and drying;

(3) Dispersing chitosan in an acetic acid aqueous solution with a mass fraction of 2 wt % in a mixing ratio of chitosan to the acetic acid aqueous solution of 1 g:60 mL, stirring and mixing, and heating at 50 ° C for 3 h until the chitosan is completely dissolved to obtain a chitosan solution; dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution in a mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride of 1:1.6, stirring and mixing, and heating at 75 ° C for 12 h to quaternize the chitosan, and then filtering, washing and drying to obtain quaternized chitosan;

Polyvinyl alcohol, glycerol and deionized water were mixed uniformly in a mass ratio of 1:2.5:1.8 to obtain a reaction precursor solution, and the reaction precursor solution was subjected to a reflux reaction at a reaction temperature of 100° C. for a reaction time of 2 h. After the reaction was completed, the modified polyvinyl alcohol was obtained by filtering, washing and drying;

Dissolving sodium alginate in deionized water to obtain a sodium alginate solution with a mass fraction of 3 wt%, adding sodium periodate to the sodium alginate solution, with a mass ratio of sodium alginate to sodium periodate of 2:1, stirring at room temperature and in a dark environment for 3 h to cause an oxidation reaction, and filtering, washing and drying after the reaction to obtain oxidized sodium alginate;

(4) adding the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate obtained in step (3) to a nanocellulose solution having a mass fraction of 0.5 wt %, wherein the mass ratio of the quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:3:0.5:0.6, and mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (1) and the modified Mxene nanosheets obtained in step (2) to the precursor mixed solution, wherein the total mass of the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixed solution, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are in a ratio of 1:0.01:0.005, and ultrasonically dispersing the mixture at an ultrasonic power of 400 W for 2 h to obtain a gel precursor solution;

(5) Glutaraldehyde is mixed evenly with a hydrochloric acid solution having a concentration of 1 mol/L to obtain a glutaraldehyde solution, wherein the mass fraction of glutaraldehyde in the glutaraldehyde solution is 2 wt %; the gel precursor solution obtained in step (4) is poured into a mold, and the glutaraldehyde solution is dripped into the gel precursor solution, wherein the ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate to the mass of the glutaraldehyde in the glutaraldehyde solution is 1:20; after all the glutaraldehyde solution is dripped, the mixture is stirred for 0.5 h to cause a cross-linking reaction, and then allowed to stand for 3 h to complete gelation, thereby obtaining a hydrogel intermediate; the hydrogel intermediate is frozen at -20°C for 5 h, then taken out, and thawed at 30°C for 5 h, and the freezing and thawing process is repeated three times to obtain a composite hydrogel;

(6) Soaking the composite hydrogel obtained in step (5) in an aniline monomer solution with a concentration of 1.5 g/L, and dropping an ammonium persulfate solution into the aniline monomer solution, wherein the mass ratio of the aniline monomer to the ammonium persulfate is 1:2. After all the ammonium persulfate solution has been dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 0.5 h, and then allowed to stand for 2 h to complete the polymerization reaction to generate polyaniline. After the reaction is completed, the mixed solution is filtered, washed, and dried in sequence to obtain a modified composite hydrogel. The modified composite hydrogel is placed on a cold plate at -50°C for directional freezing, and one side of the modified composite hydrogel is in contact with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel. After being placed on the cold plate for 50 min, the modified composite hydrogel is removed and placed in a freeze dryer, and freeze-dried at -70°C for 24 h to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix.

(7) dissolving the pyrrole monomer in a 0.5 mol/L hydrochloric acid solution, wherein the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:20, and mixing them evenly to obtain a pyrrole monomer solution. The aerogel matrix obtained in step (6) is immersed in the pyrrole monomer solution and magnetically stirred at a speed of 700 r/min for 2 h, so that the pyrrole monomer enters the pores of the aerogel matrix.

Subsequently, a 30 g/L ferric chloride solution was added to the pyrrole monomer solution, the molar ratio of the pyrrole monomer to the ferric chloride was 1:2.5, and magnetic stirring was performed at a speed of 300 r/min for 2 hours in an ice water bath environment at 0°C to react, so that the pyrrole monomer underwent in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole. After the reaction was completed, the nanocellulose-based solar interface evaporation device was obtained after filtration, washing and liquid nitrogen freeze-drying for 10 minutes.

FIG1 and FIG2 are transmission electron microscope images of the photothermal conversion material prepared in this embodiment at different magnifications, respectively. It can be seen from the figures that a large number of nano copper sulfide particles are evenly loaded on the reduced graphene oxide sheets, and the diameter of the nano copper sulfide particles is concentrated around 50 nm.

FIG3 is an infrared spectrum of graphene oxide, reduced graphene oxide, and the photothermal conversion material prepared in this embodiment. It can be seen from the figure that in the infrared spectrum curve of graphene oxide, 3417 cm ^-1 is the absorption peak of hydroxyl (-OH), 1598 cm ^-1 is the absorption peak of benzene ring structure C=C, and 1396 cm ^-1 is the absorption peak of carboxyl (C=O). In the infrared spectrum curve of reduced graphene oxide, the intensity of the corresponding absorption peak is weak. The infrared spectrum curve of the photothermal conversion material contains the corresponding absorption peak of reduced graphene oxide and the vibration peak of copper sulfide, indicating that copper sulfide is successfully loaded on the sheet of reduced graphene oxide.

FIG4 and FIG5 are scanning electron microscope images and transmission electron microscope images of the MXene nanosheets prepared in this example, respectively. It can be seen from the figures that a thin layer of transparent flaky structure appears on the surface of the titanium aluminum carbide powder etched by the lithium fluoride/hydrochloric acid system.

FIG6 is a scanning electron microscope image of the internal structure of the aerogel matrix prepared in this embodiment. It can be seen from the figure that there are a large number of micropores of about 2 μm inside the aerogel matrix, and a large number of evenly distributed rough protrusions can be observed on the inner wall of the pores. These are the photothermal conversion materials and modified MXene nanosheets attached to the inner wall of the aerogel pores.

FIG7 is a scanning electron microscope image of the solar interface evaporation device prepared in this embodiment at a low magnification. It can be seen from the figure that due to the use of directional freeze-drying in the preparation process, the ice crystals grow and arrange from bottom to top, and the interior of the solar interface evaporation device presents a parallel arranged pore structure. At the same time, some "branch-like" interlayer cross-linked structures are generated between adjacent pore structures. This is because the addition of nanocellulose increases the viscosity of the gel precursor solution and forms a stable cross-linked network with chitosan, polyvinyl alcohol and sodium alginate, overcoming the capillary force in the sublimation process of ice crystals and the expansion force in the development process of ice crystals, thereby forming a "substructure" between adjacent pore structures, which helps to improve the stability of the overall structure of the solar interface evaporation device.

FIG8 is a scanning electron microscope image of the solar interface evaporation device prepared in this embodiment at a high magnification. It can be seen from the image that the polypyrrole particles are evenly attached to the wrinkled sheet structure of the modified MXene nanosheet.

Figure 9 is a planar temperature distribution diagram of seawater and the solar interface evaporation device prepared in this embodiment under a light density of 1kW/m. It can be seen from the figure that under no light conditions (0min), the surface temperatures of seawater and the solar interface evaporation device are both low. After the initial light is given, the surface temperatures of both rise steadily. After 30 minutes of light exposure, the surface temperatures of seawater and the solar interface evaporation device tend to be stable. The infrared image shows that after 30 minutes of light exposure, the surface temperature of seawater rises by 9.6°C, while the surface temperature of the solar interface evaporation device rises by 24.3°C, indicating that the solar interface evaporation device prepared by the present invention has good light-heat conversion characteristics and can effectively use the local thermal effect to heat the seawater absorbed inside it.

FIG10 is a diagram of the surface water contact angle of the solar interface evaporation device prepared in this embodiment. It can be seen from the figure that the water droplets are quickly absorbed when they are on the surface of the solar interface evaporation device, that is, the water contact angle of the solar interface evaporation device is almost 0°, which indicates that the surface of the solar interface evaporation device prepared by the present invention has super hydrophilicity. This super hydrophilicity can ensure the rapid transportation of water inside the solar interface evaporation device, thereby significantly improving the water absorption and evaporation performance of the solar interface evaporation device.

Example 2

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, and the preparation method specifically comprises the following steps:

(1) Dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a mass fraction of 12 wt% after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion, the mass ratio of graphene oxide to L-cysteine being 1:18, and mixing and stirring until L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution with a concentration of 1.05 mol/L to the reaction solution, the mass ratio of L-cysteine to copper chloride being 3.5:1, and mixing uniformly to obtain a precursor solution, transferring the precursor solution to a reactor and heating it at 145° C. for 14 h, so that L-cysteine reacts with copper chloride to generate copper sulfide, and at the same time, graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, filtering, washing and drying the reaction product to obtain a photothermal conversion material composed of graphene oxide and copper sulfide;

(2) Add lithium fluoride to a hydrochloric acid solution with a concentration of 3.5 mol/L, the mixing ratio of lithium fluoride to hydrochloric acid solution is 1 g:22 mL, and the etching solution is obtained after being evenly mixed. Titanium aluminum carbide powder is added to the etching solution, and the mixing ratio of the etching solution to titanium aluminum carbide powder is 1 L:32 g. After magnetic stirring and heating in a water bath at 32°C for 22 h, a suspension is obtained. The suspension is washed and centrifuged with deionized water in sequence. After repeating the washing and centrifugation operations three times, the precipitate is dispersed in deionized water, and the supernatant is dried after standing to obtain Mxene nanosheets;

The Mxene nanosheets were dispersed in deionized water to form a Mxene dispersion with a concentration of 3.5 g/L. The Mxene dispersion was transferred to a shaker, polyethyleneimine was added to the Mxene dispersion, the mass ratio of the Mxene nanosheets to the polyethyleneimine was 1:0.65, and the Mxene dispersion was heated and shaken in a shaker for 1.2 h for amino modification. The heating temperature was 48°C and the shaker speed was 180 r/min. Subsequently, a dopamine solution with a concentration of 0.8 g/L was added to the Mxene dispersion at room temperature. The volume ratio of the Mxene dispersion to the dopamine solution was 10.5:1, wherein the pH value of the Tris-HCl buffer solution in the dopamine solution was 8.2. The dopamine was mixed and shaken in a shaker for 15 h to allow the dopamine to undergo in-situ oxidation self-polymerization to form polydopamine. Finally, the modified Mxene nanosheets were obtained after filtration, washing and drying.

(3) Dispersing chitosan in an acetic acid aqueous solution with a mass fraction of 2.2 wt % in a mixing ratio of chitosan to the acetic acid aqueous solution of 1 g:55 mL, stirring and mixing, and heating at 52 ° C for 2.8 h until the chitosan is completely dissolved to obtain a chitosan solution; dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution in a mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride of 1:1.65, stirring and mixing, and heating at 78 ° C for 11.5 h to quaternize the chitosan, and then filtering, washing and drying to obtain quaternized chitosan;

Polyvinyl alcohol, glycerol and deionized water were mixed uniformly in a mass ratio of 1:2.8:1.9 to obtain a reaction precursor solution, and the reaction precursor solution was subjected to a reflux reaction at a reaction temperature of 105° C. for a reaction time of 1.8 h. After the reaction was completed, the modified polyvinyl alcohol was obtained by filtering, washing and drying;

Dissolving sodium alginate in deionized water to obtain a sodium alginate solution with a mass fraction of 3.5 wt %, adding sodium periodate to the sodium alginate solution, with a mass ratio of sodium alginate to sodium periodate of 2.2:1, stirring for 3.5 h at room temperature and in a dark environment to allow an oxidation reaction to occur, and filtering, washing and drying after the reaction to obtain oxidized sodium alginate;

(4) adding the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate obtained in step (3) to a nanocellulose solution having a mass fraction of 0.8 wt %, wherein the mass ratio of the quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:3.5:0.6:0.62, and mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (1) and the modified Mxene nanosheets obtained in step (2) to the precursor mixed solution, wherein the total mass of the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixed solution, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are in a ratio of 1:0.02:0.006, and ultrasonically dispersing the mixture at an ultrasonic power of 420 W for 1.8 h to obtain a gel precursor solution;

(5) Glutaraldehyde is mixed evenly with a hydrochloric acid solution having a concentration of 1.2 mol/L to obtain a glutaraldehyde solution, wherein the mass fraction of glutaraldehyde in the glutaraldehyde solution is 2.2 wt %; the gel precursor solution obtained in step (4) is poured into a mold, and the glutaraldehyde solution is dripped into the gel precursor solution, wherein the ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate to the mass of the glutaraldehyde in the glutaraldehyde solution is 1:18; after all the glutaraldehyde solution is dripped, the mixture is stirred for 0.8 h to cause a cross-linking reaction, and then allowed to stand for 3.5 h to complete gelation, thereby obtaining a hydrogel intermediate; the hydrogel intermediate is frozen at -22°C for 4.5 h, then taken out, and thawed at 32°C for 4.5 h, and the freezing and thawing process is repeated three times to obtain a composite hydrogel;

(6) Soaking the composite hydrogel obtained in step (5) in an aniline monomer solution with a concentration of 1.8 g/L, and dropping an ammonium persulfate solution into the aniline monomer solution, wherein the mass ratio of the aniline monomer to the ammonium persulfate is 1:2.2. After all the ammonium persulfate solution has been dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 0.8 h, and then allowed to stand for 2.2 h to complete the polymerization reaction to generate polyaniline. After the reaction is completed, the mixed solution is filtered, washed, and dried in sequence to obtain a modified composite hydrogel. The modified composite hydrogel is placed on a cold plate at -52°C for directional freezing, and one side of the modified composite hydrogel is in contact with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel. After being placed on the cold plate for 45 min, the modified composite hydrogel is removed and placed in a freeze dryer, and freeze-dried at -72°C for 22 h to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix.

(7) dissolving the pyrrole monomer in a 0.8 mol/L hydrochloric acid solution, wherein the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:18, and mixing them evenly to obtain a pyrrole monomer solution. The aerogel matrix obtained in step (6) is immersed in the pyrrole monomer solution and magnetically stirred at a speed of 720 r/min for 1.8 h, so that the pyrrole monomer enters the pores of the aerogel matrix.

Subsequently, a 32 g/L ferric chloride solution was added to the pyrrole monomer solution, the molar ratio of the pyrrole monomer to the ferric chloride was 1:2.2, and magnetic stirring was performed at a speed of 320 r/min for 1.8 h in an ice water bath environment at 2°C to react, so that the pyrrole monomer underwent in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole. After the reaction, the nanocellulose-based solar interface evaporation device was obtained by filtering, washing and liquid nitrogen freeze-drying for 12 minutes.

Example 3

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, and the preparation method specifically comprises the following steps:

(1) Dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a mass fraction of 15 wt% after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion, the mass ratio of graphene oxide to L-cysteine being 1:20, and mixing and stirring until L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution with a concentration of 1.1 mol/L to the reaction solution, the mass ratio of L-cysteine to copper chloride being 4:1, and mixing uniformly to obtain a precursor solution, transferring the precursor solution to a reactor and heating it at 150° C. for 12 h, so that L-cysteine reacts with copper chloride to generate copper sulfide, and at the same time, graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, filtering, washing and drying the reaction product to obtain a photothermal conversion material composed of graphene oxide and copper sulfide;

(2) Add lithium fluoride to a hydrochloric acid solution with a concentration of 4 mol/L, the mixing ratio of lithium fluoride to hydrochloric acid solution is 1 g:20 mL, and the etching solution is obtained after being evenly mixed. Titanium aluminum carbide powder is added to the etching solution, and the mixing ratio of the etching solution to titanium aluminum carbide powder is 1 L:35 g. After magnetic stirring and heating in a water bath at 35°C for 20 h, a suspension is obtained. The suspension is washed and centrifuged with deionized water in turn. After repeating the washing and centrifugation operations four times, the precipitate is dispersed in deionized water, and the supernatant is dried after standing to obtain Mxene nanosheets;

The Mxene nanosheets were dispersed in deionized water to form a 4 g/L Mxene dispersion, the Mxene dispersion was transferred to a shaker, polyethyleneimine was added to the Mxene dispersion, the mass ratio of the Mxene nanosheets to the polyethyleneimine was 1:0.7, and the Mxene dispersion was heated and shaken in a shaker for 1.5 h for amino modification, the heating temperature was 45°C, and the shaker speed was 200 r/min; then, a dopamine solution with a concentration of 1 g/L was added to the Mxene dispersion at room temperature, the volume ratio of the Mxene dispersion to the dopamine solution was 11:1, wherein the pH value of the Tris-HCl buffer solution in the dopamine solution was 8.5, and the dopamine was mixed and shaken in a shaker for 20 h to allow the dopamine to undergo in-situ oxidation self-polymerization to form polydopamine, and finally the modified Mxene nanosheets were obtained after filtration, washing and drying;

(3) Dispersing chitosan in an acetic acid aqueous solution with a mass fraction of 2.5 wt % and a mixing ratio of chitosan to the acetic acid aqueous solution of 1 g:50 mL, stirring and mixing, and heating at 55° C. for 2.5 h until the chitosan is completely dissolved to obtain a chitosan solution; dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution, with a mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride of 1:1.7, stirring and mixing, and heating at 80° C. for 11 h to quaternize the chitosan, and then filtering, washing and drying to obtain quaternized chitosan;

Polyvinyl alcohol, glycerol and deionized water were mixed uniformly in a mass ratio of 1:3:2 to obtain a reaction precursor solution, and the reaction precursor solution was subjected to a reflux reaction at a reaction temperature of 110° C. and a reaction time of 1.5 h. After the reaction was completed, the modified polyvinyl alcohol was obtained by filtering, washing and drying;

Dissolving sodium alginate in deionized water to obtain a sodium alginate solution with a mass fraction of 4 wt%, adding sodium periodate to the sodium alginate solution, with a mass ratio of sodium alginate to sodium periodate of 2.5:1, stirring at room temperature and in a dark environment for 4 hours to allow an oxidation reaction to occur, and filtering, washing and drying after the reaction to obtain oxidized sodium alginate;

(4) adding the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate obtained in step (3) to a nanocellulose solution having a mass fraction of 1 wt%, wherein the mass ratio of the quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:4:0.6:0.65, and mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (1) and the modified Mxene nanosheets obtained in step (2) to the precursor mixed solution, wherein the total mass of the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixed solution, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are in a ratio of 1:0.03:0.007, and ultrasonically dispersing the mixture at an ultrasonic power of 450 W for 1.5 h to obtain a gel precursor solution;

(5) Glutaraldehyde is mixed evenly with a hydrochloric acid solution having a concentration of 1.5 mol/L to obtain a glutaraldehyde solution, wherein the mass fraction of glutaraldehyde in the glutaraldehyde solution is 2.5 wt %; the gel precursor solution obtained in step (4) is poured into a mold, and the glutaraldehyde solution is dripped into the gel precursor solution, wherein the ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate to the mass of the glutaraldehyde in the glutaraldehyde solution is 1:15; after all the glutaraldehyde solution is dripped, the mixture is stirred for 1 hour to cause a cross-linking reaction, and then allowed to stand for 4 hours to complete gelation, thereby obtaining a hydrogel intermediate; the hydrogel intermediate is frozen at -25°C for 4 hours, then taken out, and thawed at 35°C for 4 hours, and the freezing and thawing process is repeated four times to obtain a composite hydrogel;

(6) Soaking the composite hydrogel obtained in step (5) in a 2 g/L aniline monomer solution, and dropping an ammonium persulfate solution into the aniline monomer solution, wherein the mass ratio of the aniline monomer to the ammonium persulfate is 1:2.5. After all the ammonium persulfate solution has been dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 1 hour, and then allowed to stand for 2.5 hours to complete the polymerization reaction to generate polyaniline. After the reaction is completed, the mixed solution is filtered, washed, and dried in sequence to obtain a modified composite hydrogel. The modified composite hydrogel is placed on a cold plate at -55°C for directional freezing, and one side of the modified composite hydrogel is in contact with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel. After being placed on the cold plate for 40 minutes, the modified composite hydrogel is removed and placed in a freeze dryer, and freeze-dried at -75°C for 20 hours to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix.

(7) dissolving the pyrrole monomer in a 1 mol/L hydrochloric acid solution, wherein the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:15, and mixing them evenly to obtain a pyrrole monomer solution. The aerogel matrix obtained in step (6) is immersed in the pyrrole monomer solution and magnetically stirred at a speed of 750 r/min for 1.5 h, so that the pyrrole monomer enters the pores of the aerogel matrix.

Subsequently, a 35 g/L ferric chloride solution was added to the pyrrole monomer solution, the molar ratio of the pyrrole monomer to the ferric chloride was 1:2, and magnetic stirring was performed at a speed of 350 r/min for 1.5 h in an ice water bath environment at 5°C to react, so that the pyrrole monomer underwent in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole. After the reaction, the nanocellulose-based solar interface evaporation device was obtained after filtration, washing and liquid nitrogen freeze-drying for 15 minutes.

Example 4

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, and the preparation method specifically comprises the following steps:

(1) Dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a mass fraction of 18 wt% after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion, the mass ratio of graphene oxide to L-cysteine being 1:22, and mixing and stirring until L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution with a concentration of 1.15 mol/L to the reaction solution, the mass ratio of L-cysteine to copper chloride being 4.5:1, and mixing uniformly to obtain a precursor solution, transferring the precursor solution to a reactor and heating it at 155° C. for 11 h, so that L-cysteine reacts with copper chloride to generate copper sulfide, and at the same time, graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, filtering, washing and drying the reaction product to obtain a photothermal conversion material composed of graphene oxide and copper sulfide;

(2) Add lithium fluoride to a hydrochloric acid solution with a concentration of 4.5 mol/L, the mixing ratio of lithium fluoride to hydrochloric acid solution is 1 g:18 mL, and the etching solution is obtained after being evenly mixed. Titanium aluminum carbide powder is added to the etching solution, and the mixing ratio of the etching solution to titanium aluminum carbide powder is 1 L:38 g. After magnetic stirring and heating in a water bath at 38°C for 15 h, a suspension is obtained. The suspension is washed and centrifuged with deionized water in turn. After repeating the washing and centrifugation operations four times, the precipitate is dispersed in deionized water, and the supernatant is dried after standing to obtain Mxene nanosheets;

The Mxene nanosheets were dispersed in deionized water to form a Mxene dispersion with a concentration of 4.5 g/L. The Mxene dispersion was transferred to a shaker, polyethyleneimine was added to the Mxene dispersion, the mass ratio of the Mxene nanosheets to the polyethyleneimine was 1:0.75, and the Mxene dispersion was heated and shaken in a shaker for 1.8 h for amino modification. The heating temperature was 42°C and the shaker speed was 220 r/min. Subsequently, a dopamine solution with a concentration of 1.2 g/L was added to the Mxene dispersion at room temperature. The volume ratio of the Mxene dispersion to the dopamine solution was 11.5:1, wherein the pH value of the Tris-HCl buffer solution in the dopamine solution was 8.8. The dopamine was mixed and shaken in a shaker for 22 h to allow the dopamine to undergo in-situ oxidation self-polymerization to form polydopamine. Finally, the modified Mxene nanosheets were obtained after filtration, washing and drying.

(3) Dispersing chitosan in an acetic acid aqueous solution with a mass fraction of 2.8 wt % and a mixing ratio of chitosan to the acetic acid aqueous solution of 1 g:45 mL, stirring and mixing, and heating at 58° C. for 2.2 h until the chitosan is completely dissolved to obtain a chitosan solution; dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution, with a mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride of 1:1.75, stirring and mixing, and heating at 82° C. for 10.5 h to quaternize the chitosan, and then filtering, washing and drying to obtain quaternized chitosan;

Polyvinyl alcohol, glycerol and deionized water were mixed uniformly in a mass ratio of 1:3.2:2.1 to obtain a reaction precursor solution, and the reaction precursor solution was subjected to a reflux reaction at a reaction temperature of 115° C. and a reaction time of 1.2 h. After the reaction was completed, the modified polyvinyl alcohol was obtained by filtering, washing and drying;

Dissolving sodium alginate in deionized water to obtain a sodium alginate solution with a mass fraction of 4.5 wt %, adding sodium periodate to the sodium alginate solution, with a mass ratio of sodium alginate to sodium periodate of 2.8:1, stirring at room temperature and in a dark environment for 4.5 h to allow an oxidation reaction to occur, and filtering, washing and drying after the reaction to obtain oxidized sodium alginate;

(4) adding the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate obtained in step (3) to a nanocellulose solution having a mass fraction of 1.2 wt%, wherein the mass ratio of the quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:4.5:0.7:0.68, and mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (1) and the modified Mxene nanosheets obtained in step (2) to the precursor mixed solution, wherein the total mass of the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixed solution, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are in a ratio of 1:0.04:0.008, and ultrasonically dispersing the mixture at an ultrasonic power of 480 W for 1.2 h to obtain a gel precursor solution;

(5) Glutaraldehyde is mixed evenly with a hydrochloric acid solution having a concentration of 1.8 mol/L to obtain a glutaraldehyde solution, wherein the mass fraction of glutaraldehyde in the glutaraldehyde solution is 2.8 wt %; the gel precursor solution obtained in step (4) is poured into a mold, and the glutaraldehyde solution is dripped into the gel precursor solution, wherein the ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate to the mass of the glutaraldehyde in the glutaraldehyde solution is 1:12; after all the glutaraldehyde solution is dripped, the mixture is stirred for 1.2 h to cause a cross-linking reaction, and then allowed to stand for 4.5 h to complete gelation, thereby obtaining a hydrogel intermediate; the hydrogel intermediate is frozen at -28°C for 3.5 h, then taken out, and thawed at 38°C for 3.5 h, and the freezing and thawing process is repeated four times to obtain a composite hydrogel;

(6) Soaking the composite hydrogel obtained in step (5) in a 2.2 g/L aniline monomer solution, and dropping an ammonium persulfate solution into the aniline monomer solution, wherein the mass ratio of the aniline monomer to the ammonium persulfate is 1:2.8. After all the ammonium persulfate solution has been dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 1.2 h, and then allowed to stand for 2.8 h to complete the polymerization reaction to generate polyaniline. After the reaction is completed, the mixed solution is filtered, washed, and dried in sequence to obtain a modified composite hydrogel. The modified composite hydrogel is placed on a cold plate at -58°C for directional freezing, and one side of the modified composite hydrogel is in contact with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel. After being placed on the cold plate for 35 min, the modified composite hydrogel is removed and placed in a freeze dryer, and freeze-dried at -78°C for 15 h to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix.

(7) dissolving the pyrrole monomer in a 1.2 mol/L hydrochloric acid solution, wherein the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:12, and mixing them evenly to obtain a pyrrole monomer solution. The aerogel matrix obtained in step (6) is immersed in the pyrrole monomer solution and magnetically stirred at a speed of 780 r/min for 1.2 h, so that the pyrrole monomer enters the pores of the aerogel matrix.

Subsequently, a 38 g/L ferric chloride solution was added to the pyrrole monomer solution, the molar ratio of the pyrrole monomer to the ferric chloride was 1:1.8, and magnetic stirring was performed at a speed of 380 r/min for 1.2 h in an ice water bath environment at 8°C to react, so that the pyrrole monomer underwent in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole. After the reaction, the nanocellulose-based solar interface evaporation device was obtained after filtration, washing and liquid nitrogen freeze-drying for 18 minutes.

Example 5

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, and the preparation method specifically comprises the following steps:

(1) Graphene oxide is dispersed in deionized water, and after ultrasonic dispersion, a graphene oxide dispersion with a mass fraction of 20wt% is obtained. L-cysteine is added to the graphene oxide dispersion, and the mass ratio of graphene oxide to L-cysteine is 1:25. The mixture is mixed and stirred until the L-cysteine is completely dissolved to obtain a reaction solution. A copper chloride solution with a concentration of 1.2 mol/L is added to the reaction solution, and the mass ratio of L-cysteine to copper chloride is 5:1. The mixture is mixed and uniformly obtained to obtain a precursor solution. The precursor solution is transferred to a reactor and heated at 160°C for 10 hours, so that L-cysteine reacts with copper chloride to generate copper sulfide. At the same time, graphene oxide reacts to generate reduced graphene oxide. After the reaction is completed, the reaction product is filtered, washed and dried to obtain a photothermal conversion material composed of graphene oxide and copper sulfide.

(2) Add lithium fluoride to a hydrochloric acid solution with a concentration of 5 mol/L, the mixing ratio of lithium fluoride to hydrochloric acid solution is 1 g:15 mL, and the etching solution is obtained after being evenly mixed. Titanium aluminum carbide powder is added to the etching solution, and the mixing ratio of the etching solution to titanium aluminum carbide powder is 1 L:40 g. After magnetic stirring and heating in a 40°C water bath for 12 h, a suspension is obtained. The suspension is washed and centrifuged with deionized water in sequence. After repeating the washing and centrifugation operations five times, the precipitate is dispersed in deionized water, and the supernatant is dried after standing to obtain Mxene nanosheets;

The Mxene nanosheets were dispersed in deionized water to form a Mxene dispersion with a concentration of 5 g/L, and the Mxene dispersion was transferred to a shaker, polyethyleneimine was added to the Mxene dispersion, the mass ratio of the Mxene nanosheets to the polyethyleneimine was 1:0.8, and the Mxene dispersion was heated and shaken in a shaker for 2 hours for amino modification, the heating temperature was 40°C, and the shaking speed was 250 r/min; then, a dopamine solution with a concentration of 1.5 g/L was added to the Mxene dispersion at room temperature, and the volume ratio of the Mxene dispersion to the dopamine solution was 12:1, wherein the pH value of the Tris-HCl buffer solution in the dopamine solution was 9, and the dopamine was mixed and shaken in a shaker for 24 hours to allow the dopamine to undergo in-situ oxidation self-polymerization to form polydopamine, and finally the modified Mxene nanosheets were obtained after filtration, washing and drying;

(3) Dispersing chitosan in an acetic acid aqueous solution with a mass fraction of 3 wt % and a mixing ratio of chitosan to the acetic acid aqueous solution of 1 g:40 mL, stirring and mixing, and heating at 60 ° C for 2 h until the chitosan is completely dissolved to obtain a chitosan solution; dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution, with a mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride of 1:1.8, stirring and mixing, and heating at 85 ° C for 10 h to quaternize the chitosan, and then filtering, washing and drying to obtain quaternized chitosan;

Polyvinyl alcohol, glycerol and deionized water are uniformly mixed in a mass ratio of 1:3.5:2.2 to obtain a reaction precursor solution, and the reaction precursor solution is subjected to a reflux reaction at a reaction temperature of 120° C. and a reaction time of 1 h. After the reaction is completed, the modified polyvinyl alcohol is obtained by filtering, washing and drying;

Dissolving sodium alginate in deionized water to obtain a sodium alginate solution with a mass fraction of 5 wt%, adding sodium periodate to the sodium alginate solution, with a mass ratio of sodium alginate to sodium periodate of 3:1, stirring at room temperature and in a dark environment for 5 hours to cause an oxidation reaction, and filtering, washing and drying after the reaction to obtain oxidized sodium alginate;

(4) adding the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate obtained in step (3) to a nanocellulose solution having a mass fraction of 1.5 wt %, wherein the mass ratio of the quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:5:0.8:0.7, and mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (1) and the modified Mxene nanosheets obtained in step (2) to the precursor mixed solution, wherein the total mass of the quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixed solution, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are in a ratio of 1:0.05:0.01, and ultrasonically dispersing the mixture at an ultrasonic power of 500 W for 1 h to obtain a gel precursor solution;

(5) Glutaraldehyde is mixed evenly with a hydrochloric acid solution having a concentration of 2 mol/L to obtain a glutaraldehyde solution, wherein the mass fraction of glutaraldehyde in the glutaraldehyde solution is 3 wt %; the gel precursor solution obtained in step (4) is poured into a mold, and the glutaraldehyde solution is dripped into the gel precursor solution, wherein the ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate to the mass of the glutaraldehyde in the glutaraldehyde solution is 1:10; after all the glutaraldehyde solution is dripped, the mixture is stirred for 1.5 h to cause a cross-linking reaction, and then allowed to stand for 5 h to complete gelation, thereby obtaining a hydrogel intermediate; the hydrogel intermediate is frozen at -30°C for 3 h, then taken out, and thawed at 40°C for 3 h, and the freezing and thawing process is repeated five times to obtain a composite hydrogel;

(6) Soaking the composite hydrogel obtained in step (5) in a 2.5 g/L aniline monomer solution, and dropping an ammonium persulfate solution into the aniline monomer solution, wherein the mass ratio of the aniline monomer to the ammonium persulfate is 1:3. After all the ammonium persulfate solution has been dropped, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 1.5 h, and then allowed to stand for 3 h to complete the polymerization reaction to generate polyaniline. After the reaction is completed, the mixed solution is filtered, washed, and dried in sequence to obtain a modified composite hydrogel. The modified composite hydrogel is placed on a cold plate at -60°C for directional freezing, and one side of the modified composite hydrogel is in contact with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel. After being placed on the cold plate for 30 min, the modified composite hydrogel is removed and placed in a freeze dryer, and freeze-dried at -80°C for 12 h to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix.

(7) dissolving the pyrrole monomer in a 1.5 mol/L hydrochloric acid solution, wherein the volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:10, and mixing them evenly to obtain a pyrrole monomer solution. The aerogel matrix obtained in step (6) is immersed in the pyrrole monomer solution and magnetically stirred at a speed of 800 r/min for 1 h, so that the pyrrole monomer enters the pores of the aerogel matrix.

Subsequently, a 40 g/L ferric chloride solution was added to the pyrrole monomer solution, the molar ratio of the pyrrole monomer to the ferric chloride was 1:1.5, and magnetic stirring was performed at a speed of 400 r/min for 1 hour in an ice water bath environment at 10°C to react, so that the pyrrole monomer underwent in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole. After the reaction, the nanocellulose-based solar interface evaporation device was obtained by filtering, washing and liquid nitrogen freeze-drying for 20 minutes.

Example 6

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the mass ratio of quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate, and absolute dry nanocellulose in the nanocellulose solution is adjusted to 1:3:0.5:0.5, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Example 7

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the mass ratio of quaternized chitosan, modified polyvinyl alcohol, oxidized sodium alginate, and absolute dry nanocellulose in the nanocellulose solution is adjusted to 1:3:0.5:0.8, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Example 8

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the ratio of the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets is adjusted to 1:0.005:0.005, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Embodiment 9

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are adjusted to 1:0.08:0.005, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Example 10

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the ratio of the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets is adjusted to 1:0.01:0.001, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Embodiment 11

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device, which differs from Embodiment 1 in that, in step (4), the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets are adjusted to 1:0.01:0.015, and the other process parameters and operating steps are exactly the same as those in Embodiment 1.

Example 12

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device. The difference from Embodiment 1 is that in step (6), the concentration of the aniline monomer in the aniline monomer solution is adjusted to 1 g/L, and the other process parameters and operation steps are exactly the same as those in Embodiment 1.

Example 13

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device. The difference from Embodiment 1 is that in step (6), the concentration of the aniline monomer in the aniline monomer solution is adjusted to 3 g/L, and the other process parameters and operation steps are exactly the same as those in Embodiment 1.

Embodiment 14

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device. The difference from Embodiment 1 is that in step (7), the volume ratio of pyrrole monomer to hydrochloric acid solution is adjusted to 1:15, and the other process parameters and operation steps are exactly the same as those in Embodiment 1.

Embodiment 15

This embodiment provides a method for preparing a nanocellulose-based solar interface evaporation device. The difference from Embodiment 1 is that in step (7), the volume ratio of pyrrole monomer to hydrochloric acid solution is adjusted to 1:25, and the other process parameters and operation steps are exactly the same as those in Embodiment 1.

The water absorption performance, evaporation performance and photothermal conversion performance of the nanocellulose-based solar interface evaporation device prepared in Examples 1-15 were tested. The specific test steps are as follows:

(1) Water absorption performance

The water absorption distance in the same time is used to measure the water absorption performance of the nanocellulose-based solar interface evaporation device. The nanocellulose-based solar interface evaporation device prepared in Examples 1-15 is cut into a cylindrical sample of appropriate size. The diameter of the cylindrical sample is the same as the inner diameter of the capillary. 100 mL of simulated seawater is injected into the capillary. The cylindrical sample is inserted into the capillary so that the liquid surface of the simulated seawater just contacts the bottom surface of the cylindrical sample. The climbing distance of the simulated seawater in the cylindrical sample is observed and recorded within 360 seconds. The water absorption performance of the nanocellulose-based solar interface evaporation device is measured according to the climbing distance of the simulated seawater in the same period of time. The test is repeated 3 times and the average value is taken.

(2) Evaporation performance

The water evaporation rate is used to measure the evaporation performance of the nanocellulose-based solar interface evaporation device. The water evaporation rate of the nanocellulose-based solar interface evaporation device prepared in Examples 1-15 is tested by a homemade seawater evaporation experimental device, as shown in Figure 11. The seawater evaporation experimental device consists of a xenon lamp, a beaker, a balance, thermal insulation foam and absorbent cotton thread. The xenon lamp is used to emit simulated sunlight and directly illuminate the surface of the solar interface evaporation device. The balance is used to record the mass change of the simulated seawater in the beaker during the experiment. The thermal insulation foam is used to isolate the simulated sunlight. The absorbent cotton thread is used to transport the simulated seawater in the beaker to the solar interface evaporation device, and the evaporation mass of the simulated seawater within 1 hour is recorded. The test is repeated 3 times and the average value is taken.

The water evaporation rate is calculated using the following formula:

Where Δm is the mass of simulated seawater evaporated in 1 h (kg), A is the area of the solar interface evaporation device exposed to simulated sunlight (m ² ), and V is the water evaporation rate (kg/m ² /h).

(3) Photothermal conversion performance

The photothermal conversion efficiency is used to measure the photothermal conversion performance of the nanocellulose-based solar interface evaporation device. Before calculating the photothermal conversion efficiency, it is necessary to calculate the sensible heat when simulating seawater evaporation. The calculation formula is as follows:

Where Q is the sensible heat per unit mass of simulated seawater (J/kg), _T2 is the surface temperature of the solar interface evaporation device after the evaporation test, _T1 is the initial temperature of the surface of the solar interface evaporation device, and c is the specific heat of simulated seawater from 30°C to 100°C (taken as 4.2J/g/K).

The photothermal conversion efficiency is calculated using the following formula:

Where η is the photothermal conversion efficiency (%), m' is the water evaporation rate (kg/m/h) after subtracting the evaporation rate under dark conditions (0.053kg/m/h), _LV is the latent heat of phase change from liquid to gas of simulated seawater (taken as 2260kJ/kg), and _Pin is the power density of solar energy input to the surface of the solar interface evaporation device.

The test and calculation results are shown in Table 1.

Table 1

Simulated seawater climbing distance cm Water evaporation rate kg/m ² /h Photothermal conversion efficiency% Example 1 5.5 2.33 92.3 Example 2 5.6 2.48 92.8 Example 3 5.8 2.50 93.0 Example 4 6.3 2.57 93.5 Example 5 6.2 2.62 93.6 Example 6 2.5 1.77 73.2 Example 7 5.0 1.86 76.7 Example 8 3.1 1.49 71.6 Embodiment 9 4.7 1.55 73.7 Example 10 3.6 1.52 72.5 Embodiment 11 5.2 1.58 74.2 Example 12 3.3 1.64 74.8 Example 13 4.6 1.70 75.2 Embodiment 14 4.4 1.73 75.5 Embodiment 15 4.1 1.65 75.1

It can be seen from the data in Table 1 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the nanocellulose-based solar interface evaporation devices prepared in Examples 1-5 are higher than those in Examples 6-15, which indicates that the nanocellulose-based solar interface evaporation device prepared in the present invention has excellent water absorption performance, evaporation performance and photothermal conversion performance.

It can be seen from the test data of Example 1, Example 6 and Example 7 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 6 are lower than those in Example 1. This is because the amount of absolute dry nanocellulose added in Example 6 is too low, which affects the internal multi-porous structure of the aerogel matrix and also affects the improvement of the hydrophilicity of the aerogel matrix, resulting in a decrease in the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. The water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 7 are lower than those in Example 1. This is because the amount of absolute dry nanocellulose added in Example 7 is too high, which not only affects the internal multi-porous structure of the aerogel matrix, but also causes the viscosity of the gel precursor solution to be too high, affecting the dispersion uniformity of the photothermal conversion material and the modified Mxene nanosheets in the gel precursor solution, thereby resulting in a decrease in the evaporation performance and photothermal conversion performance of the solar interface evaporation device.

It can be seen from the test data of Example 1, Example 8 and Example 9 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 8 are lower than those in Example 1. This is because the amount of photothermal conversion material added in Example 8 is too low, and the photothermal conversion material cannot effectively exert its ability to absorb sunlight. At the same time, the photothermal conversion material has a certain hydrophilicity, and its addition amount is too low, which will also affect the simulated seawater climbing distance, and ultimately lead to a decrease in the water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. The water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 9 are lower than those in Example 1. This is because the amount of photothermal conversion material added in Example 9 is too high, and the photothermal conversion material is prone to agglomeration in the gel precursor solution, which affects its photothermal conversion performance, and ultimately leads to a decrease in the evaporation performance and photothermal conversion performance of the solar interface evaporation device.

It can be seen from the test data of Example 1, Example 10 and Example 11 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 10 are lower than those in Example 1. This is because the amount of modified Mxene nanosheets added in Example 10 is too low, and the modified Mxene nanosheets cannot effectively exert their ability to absorb sunlight. At the same time, the modified Mxene nanosheets have a certain hydrophilicity, and their addition is too low, which will also affect the simulated seawater climbing distance, and ultimately lead to the decrease of water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. The water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 11 are lower than those in Example 1. This is because the amount of modified Mxene nanosheets added in Example 11 is too high, and due to their inherent high surface energy and interfacial van der Waals effect, they are prone to agglomeration in the gel precursor solution, which affects their photothermal conversion performance, and ultimately leads to the decrease of evaporation performance and photothermal conversion performance of the solar interface evaporation device.

It can be seen from the test data of Example 1, Example 12 and Example 13 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 12 are lower than those in Example 1. This is because the concentration of the aniline monomer solution in Example 12 is too low. On the one hand, polyaniline itself is a hydrophilic material. If its addition amount is too low, it will directly lead to a decrease in the hydrophilicity of the solar interface evaporation device, thereby affecting the water absorption and evaporation performance of the solar interface evaporation device; on the other hand, there is a synergistic effect between the short-chain polyaniline nanofibers formed by the self-polymerization of the aniline monomer and the modified Mxene nanosheets and the photothermal conversion material. If its addition amount is too low, it will directly affect the photothermal conversion ability of the modified Mxene nanosheets and the photothermal conversion material, thereby indirectly leading to a decrease in the photothermal conversion performance of the solar interface evaporation device. However, the water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 13 are lower than those in Example 1. This is because the concentration of the aniline monomer solution in Example 13 is too high, and short-chain polyaniline nanofibers cannot be formed on the surface of the modified MXene nanosheets, which affects the full photothermal conversion capacity of the modified MXene nanosheets, resulting in a decrease in the evaporation performance and photothermal conversion performance of the solar interface evaporation device.

It can be seen from the test data of Example 1, Example 14 and Example 15 that the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 14 are lower than those in Example 1. This is because the amount of pyrrole monomer added in Example 14 is too high, and the excessive amount of polypyrrole generated will block some of the pores inside the solar interface evaporation device, affecting the transmission of water and the escape of water vapor, resulting in reduced water absorption performance, evaporation performance and photothermal conversion performance of the solar interface evaporation device. However, the simulated seawater climbing distance, water evaporation rate and photothermal conversion efficiency of the solar interface evaporation device prepared in Example 15 are lower than those in Example 1. This is because the amount of pyrrole monomer added in Example 15 is too low. On the one hand, polypyrrole itself is a hydrophilic material. If its amount is too low, the hydrophilicity of the solar interface evaporation device will be reduced, thereby affecting the water absorption and evaporation performance of the solar interface evaporation device. On the other hand, polypyrrole, as a light absorption site, can significantly improve the light capture ability of the solar interface evaporation device. If its production amount is too low, it will directly affect the photothermal conversion performance of the solar interface evaporation device. At the same time, due to the synergistic effect between polypyrrole and the modified Mxene nanosheets, if the production amount of polypyrrole is too low, it will also affect the full play of the photothermal conversion ability of the modified Mxene nanosheets to a certain extent, thereby indirectly affecting the photothermal conversion performance of the solar interface evaporation device.

The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A method for preparing a nanocellulose-based solar interface evaporation device, characterized in that the preparation method comprises: (I) dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion liquid after ultrasonic dispersion, adding L-cysteine to the graphene oxide dispersion liquid, and mixing and stirring under sealed conditions until the L-cysteine is completely dissolved to obtain a reaction solution; adding a copper chloride solution to the reaction solution, and mixing evenly to obtain a precursor solution, and transferring the precursor solution to a reactor for heating, so that L-cysteine and copper chloride react to generate copper sulfide, and at the same time, the graphene oxide reacts to generate reduced graphene oxide, and after the reaction is completed, the reaction product is filtered, washed and dried to obtain a photothermal conversion material composed of reduced graphene oxide and copper sulfide; (II) adding lithium fluoride to a hydrochloric acid solution, mixing uniformly to obtain an etching solution, adding titanium aluminum carbide powder to the etching solution, stirring magnetically and heating in a water bath to obtain a suspension, washing the suspension with deionized water and centrifuging in sequence, repeating the washing and centrifuging operations at least three times, dispersing the precipitate in deionized water, letting it stand, and drying the supernatant to obtain Mxene nanosheets; dispersing the Mxene nanosheets in deionized water to form an Mxene dispersion, transferring the Mxene dispersion to a shaker, adding polyethyleneimine to the Mxene dispersion, and heating and shaking in a shaker to perform amino modification; subsequently, adding a dopamine solution to the Mxene dispersion at room temperature, mixing and shaking in a shaker to allow dopamine to undergo in-situ oxidation self-polymerization to form polydopamine, and finally filtering, washing, and drying to obtain modified Mxene nanosheets; (III) dispersing chitosan in an acetic acid aqueous solution, mixing and stirring, and heating until the chitosan is completely dissolved to obtain a chitosan solution, dropping 2,3-epoxypropyltrimethylammonium chloride into the chitosan solution, mixing and stirring, and heating to quaternize the chitosan, and then filtering, washing, and drying to obtain quaternized chitosan; uniformly mixing polyvinyl alcohol, glycerol, and deionized water to obtain a reaction precursor solution, heating the reaction precursor solution to reflux reaction, filtering, washing, and drying after the reaction to obtain modified polyvinyl alcohol; dissolving sodium alginate in deionized water to obtain a sodium alginate solution, adding sodium periodate to the sodium alginate solution, stirring at room temperature and in the dark to cause an oxidation reaction, and filtering, washing, and drying after the reaction to obtain oxidized sodium alginate; (IV) adding the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate obtained in step (III) to the nanocellulose solution, mixing them evenly to obtain a precursor mixed solution, adding the photothermal conversion material obtained in step (I) and the modified Mxene nanosheets obtained in step (II) to the precursor mixed solution, and obtaining a gel precursor solution after ultrasonic dispersion; (V) mixing glutaraldehyde and hydrochloric acid solution uniformly to obtain glutaraldehyde acid solution, pouring the gel precursor solution obtained in step (IV) into a mold, dropping the glutaraldehyde acid solution into the gel precursor solution, mixing and stirring to cause a cross-linking reaction, and standing at room temperature after the reaction to gel to obtain a hydrogel intermediate; freezing the hydrogel intermediate under low temperature conditions for a period of time, then taking it out and thawing it for a period of time, repeating the freezing and thawing process at least three times to obtain a composite hydrogel; (VI) soaking the composite hydrogel obtained in step (V) in an aniline monomer solution, dropping an ammonium persulfate solution into the aniline monomer solution, mixing and stirring, and then standing to react to generate polyaniline. After the reaction is completed, filtering, washing and drying are performed in sequence to obtain a modified composite hydrogel, placing the modified composite hydrogel on a cold plate for directional freezing, contacting one side of the modified composite hydrogel with the surface of the cold plate to form a temperature gradient in the vertical direction inside the modified composite hydrogel, and after being placed on the cold plate for a period of time, removing the modified composite hydrogel and placing it in a freeze dryer for freeze drying to form vertical channels inside the modified composite hydrogel to obtain an aerogel matrix; (VII) dissolving pyrrole monomer in hydrochloric acid solution, mixing evenly to obtain pyrrole monomer solution, immersing the aerogel matrix obtained in step (VI) in the pyrrole monomer solution and performing magnetic stirring to allow the pyrrole monomer to enter the pores of the aerogel matrix; subsequently, adding ferric chloride solution to the pyrrole monomer solution, performing magnetic stirring in an ice-water bath environment to react, so that the pyrrole monomer undergoes in-situ oxidation self-polymerization on the surface of the aerogel matrix and the inner wall of the pores to form polypyrrole, and after the reaction is completed, filtering, washing and liquid nitrogen freeze-drying to obtain the nanocellulose-based solar interface evaporation device. 2. The preparation method according to claim 1, characterized in that, in step (I), the mass fraction of graphene oxide in the graphene oxide dispersion is 10-20wt%; The mass ratio of graphene oxide to L-cysteine in the graphene oxide dispersion is 1:(15-25); The concentration of copper chloride in the copper chloride solution is 1-1.2 mol/L; The mass ratio of L-cysteine in the reaction solution to copper chloride in the copper chloride solution is (3-5):1; The heating temperature of the precursor solution is 140-160°C; The heating time of the precursor solution is 10 to 15 hours. 3. The preparation method according to claim 1, characterized in that in step (II), the concentration of the hydrochloric acid solution is 3-5 mol/L; The mixing ratio of the lithium fluoride and the hydrochloric acid solution is 1g: (15-25)mL; The mixing ratio of the etching solution and the titanium aluminum carbide powder is 1L: (30-40)g; The temperature of the water bath heating when the etching solution and the titanium aluminum carbide powder are mixed is 30-40° C.; The water bath heating time when the etching solution and the titanium carbide aluminum powder are mixed is 12 to 24 hours; The concentration of the Mxene nanosheets in the Mxene dispersion is 3-5 g/L; The mass ratio of the Mxene nanosheets to the polyethyleneimine in the Mxene dispersion is 1:(0.6-0.8); The heating temperature of the amination-modified heating oscillation is 40-50°C; The shaking speed of the amino-modified heated oscillating table is 150-250 r/min; The heating and oscillating modification time of the amino modification is 1 to 2 hours; The dopamine solution consists of dopamine and Tris-HCl buffer solution; The pH value of the Tris-HCl buffer solution is 8-9; The concentration of dopamine in the dopamine solution is 0.5-1.5 g/L; The volume ratio of the Mxene dispersion to the dopamine solution is (10-12):1; The Mxene dispersion and the dopamine solution are mixed and shaken in a shaker for 12 to 24 hours. 4. The preparation method according to claim 1, characterized in that, in step (III), the mass fraction of acetic acid in the acetic acid aqueous solution is 2-3wt%; The mixing ratio of chitosan and acetic acid aqueous solution is 1g: (40-60)mL; The heating temperature when the chitosan and the acetic acid aqueous solution are mixed is 50-60°C; The stirring time when the chitosan and the acetic acid aqueous solution are mixed is 2 to 3 hours; The mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride in the chitosan solution is 1:(1.6-1.8); The heating temperature of the chitosan solution and 2,3-epoxypropyltrimethylammonium chloride during the quaternization modification process is 75-85°C; The stirring time of the chitosan solution and 2,3-epoxypropyltrimethylammonium chloride during the quaternization modification process is 10 to 12 hours; The mass ratio of the polyvinyl alcohol, glycerol and deionized water is 1:(2.5-3.5):(1.8-2.2); The reaction temperature of the heating reflux reaction of the reaction precursor solution is 100-120°C; The reaction time of the heating reflux reaction of the reaction precursor solution is 1 to 2 hours; The mass fraction of sodium alginate in the sodium alginate solution is 3-5wt%; The mass ratio of sodium alginate to sodium periodate in the sodium alginate solution is (2-3):1; The stirring time of the sodium alginate solution and sodium periodate during the oxidation reaction is 3 to 5 hours. 5. The preparation method according to claim 1, characterized in that in step (IV), the mass ratio of the quaternized chitosan, the modified polyvinyl alcohol, the oxidized sodium alginate and the absolute dry nanocellulose in the nanocellulose solution is 1:(3-5):(0.5-0.8):(0.6-0.7); The mass fraction of the nanocellulose solution is 0.5-1.5wt%; The ratio of the total mass of quaternized chitosan, modified polyvinyl alcohol and oxidized sodium alginate in the precursor mixture, the mass of the photothermal conversion material and the mass of the modified Mxene nanosheets is 1:(0.01-0.05):(0.005-0.01); The ultrasonic power of ultrasonic dispersion of the precursor mixed solution, the photothermal conversion material and the modified Mxene nanosheets is 400-500W; The ultrasonic dispersion time of the precursor mixed solution, the photothermal conversion material and the modified Mxene nanosheets is 1 to 2 hours. 6. The preparation method according to claim 1, characterized in that in step (V), the concentration of the hydrochloric acid solution is 1-2 mol/L; The mass fraction of glutaraldehyde in the glutaraldehyde acid solution is 2-3wt%; The ratio of the total mass of the quaternized chitosan, the modified polyvinyl alcohol and the oxidized sodium alginate in the gel precursor solution to the mass of the glutaraldehyde in the glutaraldehyde acid solution is 1:(10-20); After all the glutaraldehyde solution is added dropwise, the mixture is stirred for 0.5-1.5 hours to allow a cross-linking reaction to occur, and then allowed to stand for 3-5 hours to complete gelation; The freezing temperature of the hydrogel intermediate is -20 to -30°C; The freezing time of the hydrogel intermediate is 3 to 5 hours; The thawing temperature of the hydrogel intermediate is 30-40°C; The thawing time of the hydrogel intermediate is 3 to 5 hours. 7. The preparation method according to claim 1, characterized in that in step (VI), the concentration of the aniline monomer in the aniline monomer solution is 1.5-2.5 g/L; The mass ratio of the aniline monomer in the aniline monomer solution to the ammonium persulfate in the ammonium persulfate solution is 1:(2-3); After all the ammonium persulfate solution is added dropwise, the mixed solution consisting of the aniline monomer solution and the ammonium persulfate solution is magnetically stirred for 0.5 to 1.5 hours, and then allowed to stand for 2 to 3 hours to complete the polymerization reaction to generate polyaniline; The temperature of the cold plate is -50~-60°C; The modified composite hydrogel is placed on a cold plate for 30 to 50 minutes; The freeze drying temperature of the modified composite hydrogel in the freeze dryer is -70 to -80°C; The freeze drying time of the modified composite hydrogel in the freeze dryer is 12 to 24 hours. 8. The preparation method according to claim 1, characterized in that in step (VII), the concentration of the hydrochloric acid solution is 0.5-1.5 mol/L; The volume ratio of the pyrrole monomer to the hydrochloric acid solution is 1:(10-20); The speed of magnetic stirring when the aerogel matrix is immersed in the pyrrole monomer solution is 700-800 r/min; The magnetic stirring time when the aerogel matrix is immersed in the pyrrole monomer solution is 1 to 2 hours; The molar ratio of the pyrrole monomer in the pyrrole monomer solution to the ferric chloride in the ferric chloride solution is 1:(1.5-2.5); The concentration of ferric chloride in the ferric chloride solution is 30-40 g/L; The ice water bath temperature of the pyrrole monomer solution and the ferric chloride solution is 0-10°C; The rotation speed of the magnetic stirring of the pyrrole monomer solution and the ferric chloride solution is 300-400 r/min; The magnetic stirring time of the pyrrole monomer solution and the ferric chloride solution is 1 to 2 hours; The liquid nitrogen freeze-drying time is 10 to 20 minutes. 9. A nanocellulose-based solar interface evaporation device prepared by the preparation method according to any one of claims 1 to 8. 10. Use of the nanocellulose-based solar interface evaporation device according to claim 9, characterized in that the nanocellulose-based solar interface evaporation device is used for seawater desalination.