A Ti3C2-based solar interfacial evaporator, its preparation method and application

Abstract

This invention discloses a Ti3C2-based solar interface evaporator, its preparation method, and its application, belonging to the field of photothermal evaporator technology. The invention employs a layered structural design, proposing a gel construction strategy of vertical pore structure – disordered porous structure to achieve thermal positioning and management during the evaporation process. Effective thermal management and rapid water transfer are achieved through the difference in heat conduction and water transport capabilities between vertical and disordered pores. Using widely available, low-cost, and eco-friendly polyvinyl alcohol and chitosan as precursors, and two-dimensional layered Ti3C2 with high light absorption capacity, excellent photothermal conversion efficiency, and good chemical stability as the base photothermal material, combined with bentonite with low thermal conductivity and excellent hydrophilicity, a novel three-dimensional photothermal gel evaporator is designed through evaporator structure regulation, layered thermal positioning, and the construction of a low enthalpy of evaporation system.

Description

Technical Field

[0001] This invention belongs to the field of photothermal evaporator technology, and particularly relates to a Ti3C2-based solar interface evaporator, its preparation method, and its application. Background Technology

[0002] Extracting freshwater from seawater or polluted environments has practical value, and interfacial solar evaporation (ISSG) technology has become a widely accepted freshwater harvesting technology due to its low cost, high efficiency, lack of environmental pollution, and near-zero carbon emissions. Although significant progress has been made in salt-tolerant high-performance evaporators, most existing salt-tolerant high-performance evaporators are limited to low-salinity brine and cannot meet the requirements for continuous use and high-concentration wastewater (especially industrial wastewater with a salt concentration of 10–20 wt%). During desalination, salt deposition occurs at the evaporation site as evaporation continues, especially in high-salinity brine, which may reduce the evaporation rate or even cause the evaporator to fail.

[0003] Currently, strategies for improving the salt resistance of interfacial solar evaporators can be mainly divided into two types: "desalination" and "salt-free". "Desalination" strategies primarily include physical cleaning, localized crystallization, and gravity-assisted cleaning. These methods not only increase production costs but also limit practical application due to over-reliance on passive diffusion. Furthermore, the nucleation, crystallization, and gravity shedding of salt crystals all require time, which also leads to a decrease in evaporation rate. "Salt-free" strategies include ion repulsion, hydrophobic surface modification, back diffusion and convection, and non-contact evaporation. While ion repulsion and non-contact evaporation designs have achieved significant success in salt resistance, their evaporation rates are relatively low (<1.3 kg·m³). -2 ·h -1 The operational stability is poor. Currently, hydrophobic surface modification and back diffusion and convection are the most widely adopted salt-tolerant strategies. These are mainly based on convection and diffusion driven by salinity differences, which promptly transport salt ions on the evaporation surface or interface back to the bulk water below. To ensure timely replenishment and dilution of brine on the evaporation surface, the rate at which water is transported to the evaporation surface should be effectively controlled. Existing evaporators with random channel structures cannot meet evaporation requirements due to insufficient water transport capacity, and are prone to salt precipitation (see...). Figure 1 (see section (a)). Evaporators with vertical pore structures will increase heat transfer losses to the open water body at the bottom due to excessive water delivery (see section (a)). Figure 1 (part (b) of the text).

[0004] Constructing vertically oriented pore structures is one of the most widely adopted strategies for improving evaporation rates and salt tolerance in solar-driven interfacial desalination. To enhance the salt removal performance of vertically oriented pore structures, evaporators are typically designed as superhydrophilic gel networks. Therefore, the vertically oriented pore microstructures can utilize capillary forces to deliver sufficient water to the evaporation surface through interconnected channels within the evaporator. However, in highly hydrophilic network structures, water transport and heat conduction losses are positively correlated, leading to a simultaneous increase in thermal localization and water delivery capabilities.

[0005] Therefore, how to solve the shortcomings of existing evaporators, such as low solar energy conversion efficiency, large heat loss during evaporation, and slow mass transfer, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a Ti3C2-based solar interface evaporator, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a Ti3C2-based solar interface evaporator, which consists of a photothermal evaporation layer with a vertically arranged pore structure and a substrate layer with a disordered porous structure. The photothermal evaporation layer contains a polydopamine / Ti3C2 composite material; the base layer contains bentonite; and the matrix material of both the photothermal evaporation layer and the base layer is a polyvinyl alcohol / chitosan composite hydrogel.

[0008] This invention constructs a Ti3C2-based solar interface evaporator that simultaneously possesses a vertically arranged pore structure and a disordered porous structure. The ordered vertical pore structure enhances light absorption capacity while strengthening the transfer of water to the evaporation interface; while the disordered porous structure weakens the heat transfer from the photothermal evaporation layer to the water body. As a result, the Ti3C2-based solar interface evaporator has advantages such as high evaporation efficiency and low heat loss.

[0009] Furthermore, the photothermal evaporation layer is prepared by an ice crystal template method using polydopamine / Ti3C2 composite material, chitosan, polyvinyl alcohol, and a crosslinking agent.

[0010] This invention uses polyvinyl alcohol and chitosan as matrix materials, which have the advantages of wide availability, low cost, and eco-friendly safety; the Ti3C2 in the polydopamine / Ti3C2 composite material has the advantages of high light absorption capacity, excellent photothermal conversion efficiency, good chemical stability and controllability.

[0011] Furthermore, the base layer is prepared by freeze casting using bentonite, chitosan, polyvinyl alcohol, and a crosslinking agent.

[0012] The role of bentonite in this invention is as follows: (1) By promoting the gelation of PVA / CS gel, the growth resistance of ice crystals in the directional freezing process can be controlled; (2) Bentonite has low thermal conductivity. When used as a component of the base layer, combined with Ti3C2 material with high thermal conductivity as a component of the photothermal evaporation layer, the thermal positioning ability between different layers in the evaporator can be further enhanced; (3) As a hydrophilic filler material, bentonite can further reduce the enthalpy of evaporation.

[0013] Furthermore, the bentonite is exfoliated bentonite; the exfoliated bentonite is prepared by liquid-phase exfoliation.

[0014] Furthermore, the preparation method of the polydopamine / Ti3C2 composite material includes: adding dopamine hydrochloride to a Ti3C2 solution for oxidative self-polymerization, and then washing, dehydrating and drying to obtain the polydopamine / Ti3C2 composite material.

[0015] Furthermore, the mass ratio of Ti3C2 to dopamine hydrochloride in the Ti3C2 solution is 1:1; the oxidation self-polymerization temperature is room temperature, and the oxidation self-polymerization time is 24 hours; the washing reagent is ultrapure water, the washing is performed twice, and the washing method is centrifugation at 8000 rpm; the dehydration method is centrifugation; and the drying method is freeze drying for 24 hours.

[0016] Furthermore, the Ti3C2 in the Ti3C2 solution is obtained by selectively etching the MAX phase precursor titanium aluminum carbide (Ti3AlC2) using hydrogen fluoride as the etching solution.

[0017] This invention provides a method for preparing a Ti3C2-based solar interfacial evaporator as described above, comprising the following steps: Add polydopamine / Ti3C2 composite material suspension to chitosan solution, mix well, then add polyvinyl alcohol solution and stir to obtain solution A; add bentonite suspension to chitosan solution, mix well, then add polyvinyl alcohol solution and stir to obtain solution B. A crosslinking agent is added to solution A, and the resulting mixture A is then transferred to a mold for in-situ gelation to obtain a polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material. A crosslinking agent is added to solution B, and the resulting mixture B is then transferred to a mold containing the polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material. The mixture is then subjected to ultra-low temperature freezing and freeze-drying to form a bentonite-polyvinyl alcohol / chitosan gel material on the surface of the polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material, thus obtaining the Ti3C2-based solar interface evaporator.

[0018] This invention selects polyvinyl alcohol and chitosan, both environmentally friendly polymers with abundant hydrophilic groups, to form a double-crosslinked gel network. The resulting composite hydrogel has a low enthalpy of vaporization, which is beneficial for the dissipation of water molecules during interfacial evaporation. The hydrophilic photothermal material polydopamine / Ti3C2 and the hydrophilic filler bentonite are introduced to further reduce the enthalpy of vaporization. By controlling the ice crystal growth resistance during the preparation process, a layered pore structure is constructed, which enhances the thermal positioning function during evaporation.

[0019] Furthermore, in solutions A and B, the ratio of chitosan solution, polydopamine / Ti3C2 composite material suspension or bentonite and polyvinyl alcohol solution is 1.75g:5mL:1.5g.

[0020] Furthermore, in solutions A and B, the concentration of chitosan solution is 2 wt%, the concentration of polydopamine / Ti3C2 composite material suspension is 15 mg / mL, and the concentration of polyvinyl alcohol solution is 5 wt%.

[0021] Furthermore, the in-situ gelation temperature is room temperature, and the in-situ gelation time is 10 minutes.

[0022] Furthermore, the ultra-low temperature freezing temperature is -80°C, and the ultra-low temperature freezing time is 30 minutes.

[0023] The present invention also provides an application of the Ti3C2-based solar interface evaporator as described above in the production of clean water.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects: To address the problems of high heat loss, poor mechanical properties, and excessive photothermal material load associated with vertical pore structures in evaporators, this invention employs a layered structural design and proposes a gel construction strategy combining vertical pore structures and disordered porous structures to achieve thermal positioning and management during the evaporation process. By leveraging the difference in heat conduction and water transport capabilities between vertical and disordered pores, effective thermal management and rapid water transfer are achieved. Using widely available, low-cost, and eco-friendly polyvinyl alcohol and chitosan as precursors, and two-dimensional layered Ti3C2 as the base photothermal material (possessing high light absorption capacity, excellent photothermal conversion efficiency, and good chemical stability), combined with bentonite (possessing low thermal conductivity and excellent hydrophilicity), a novel three-dimensional photothermal gel evaporator was designed through evaporator structure regulation, layered thermal positioning, and the construction of a low enthalpy of vaporization system.

[0025] The Ti3C2-based solar interface evaporator provided by this invention achieves a surface temperature of 90.4°C in a dry state and 42.7°C in a wet state under simulated light source irradiation of 1 Sun; the evaporation rate of the Ti3C2-based solar interface evaporator can reach 4.08 kg·m³. -2 ·h -1 Compared to gel evaporators with non-layered designs, this method improves overall thermal management and evaporation efficiency. In experiments simulating seawater evaporation, it can achieve continuous evaporation for 5 hours under 10wt% saline conditions without significant salt crystallization on the surface.

[0026] This invention achieves continuous composite bonding of a polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel layer and a bentonite-polyvinyl alcohol / chitosan gel layer by sequentially performing in-situ gelation of a polydopamine / Ti3C2 composite material mixture and ultra-low temperature freeze-drying molding with a bentonite mixture in the same mold. This one-piece molding process avoids the secondary assembly steps required by traditional multilayer materials using adhesives or hot pressing, effectively eliminating interlayer interface defects and the risk of physical delamination, ensuring a strong chemical bond between the two gel layers. The resulting evaporator exhibits good integrity and tight interfacial bonding, and is less prone to delamination or detachment during long-term photothermal evaporation, significantly improving structural stability and durability. It also simplifies the preparation process, facilitating large-scale application. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The diagram shows the structure of an existing evaporator with a channel structure, where (a) is an evaporator with a random channel structure and (b) is an evaporator with a vertical channel structure. Figure 2 This is a schematic diagram of the structure of the Ti3C2-based solar interface evaporator provided by the present invention; Figure 3 This is a schematic diagram illustrating the fabrication process of the Ti3C2-based solar interfacial evaporator provided by the present invention. Figure 4 This is a physical image of the equipment used for testing the photothermal evaporation performance of this invention; Figure 5 A schematic diagram of the 3D model structure of the PTB-PC gel evaporator provided by the present invention (a) and a physical image of the PTB-PC gel evaporator prepared in Example 3 (b), wherein the left side of part (b) is a side view and the right side is a top view; Figure 6The images are scanning electron microscope (SEM) images of PT-PC gel material and B-PC gel material in the PTB-PC gel evaporator prepared in Example 3, where (a) and (b) are PT-PC gel material, (c) and (d) are B-PC gel material, (a) and (c) are 500 μm, and (b) and (d) are 100 μm. Figure 7 The images show scanning electron microscope (SEM) images, elemental spectra, and EDS spectra of the PT-PC gel material inside the PTB-PC gel evaporator prepared in Example 3. In the images, (a) is a scanning electron microscope image, (b) to (e) are elemental spectra of C, N, Si, and Ti, respectively, and (f) is an EDS spectrum. The inset shows the elemental content. Figure 8 The images show the scanning electron microscope (SEM) image, elemental spectrum, and EDS energy spectrum of the B-PC gel material inside the PTB-PC gel evaporator prepared in Example 3. In the images, (a) is a scanning electron microscope image, (b) to (e) are elemental spectra of C, N, Si, and Ti, respectively, and (f) is an EDS energy spectrum. The inset shows the elemental content. Figure 9 XRD patterns of PC, BTex and B-PC (a), XRD patterns of PC, P-PC, T-PC and PT-PC (b), FT-IR spectra of PC, T-PC, P-PC and PT-PC (c), and FT-IR spectra of PC, BTex and B-PC (d~e). Figure 10 XPS total spectrum (a) and C 1s spectrum (b), O 1s spectrum (c), and Ti2p spectrum (d) for PC, T-PC, P-PC, and PT-PC. Figure 11 XPS total spectra of PC, BT, and B-PC (a), and C 1s spectrum (b), Al 2p spectrum (c), O 1s spectrum (d), and N 1s spectrum (e) of PC, BTex, and B-PC. Figure 12 The following are the surface temperatures of the PTB-PC gel evaporator prepared in Example 3 under dry conditions and without light (a), the surface temperatures of the PT-PC gel material prepared in Example 3 under dry conditions and with one solar irradiance (b), the surface temperatures of the PTB-PC gel evaporator prepared in Example 3 under dry conditions and with one solar irradiance (c), and the corresponding 3D temperature distribution maps (d~f), where (d) is the 3D temperature distribution map of (a), (e) is the 3D temperature distribution map of (b), and (f) is the 3D temperature distribution map of (c). Figure 13Infrared thermal images of the surface temperature of the PT-PC gel material and PTB-PC gel evaporator prepared in Example 3 under wet conditions and at one solar irradiance intensity, showing the change over time. (a) is the PT-PC gel material, and (b) is the PTB-PC gel evaporator. Figure 14 Infrared thermal imaging of the side temperature of the PTB-PC gel evaporator prepared in Example 3 under wet conditions and with 1 solar irradiance intensity as a function of time. Figure 15 The hydrophilicity of the PT-PC gel material prepared in Example 3 is shown in (a), the hydrophilicity of the B-PC gel material is shown in (b), the internal pore structure of the PT-PC gel material is shown in (c), and the internal pore structure of the B-PC gel material is shown in (d). Figure 16 The long-term evaporation stability of the PTB-PC gel evaporator prepared in Example 3 under one solar irradiance intensity; Figure 17 The stability of the PTB-PC gel evaporator prepared in Example 3 in water, wherein (a) is immersion for 0 days and (b) is immersion for 7 days; Figure 18 The image shows the PTB-PC gel evaporator prepared in Example 3 after being continuously immersed in a 10 wt% NaCl solution for 5 hours. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] In this embodiment of the invention, room temperature refers to "25±2℃".

[0031] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0032] Detailed information on the reagents used in this invention is shown in Table 1. The water used is ultrapure water with a resistivity of 18.2 MΩ·cm.

[0033] Table 1

[0034] Note: "—" indicates that there is no definite chemical formula.

[0035] The parameters of the instruments and related equipment used in this invention are shown in Table 2.

[0036] Table 2

[0037] In the following examples and comparative examples, The PVA solution is prepared by dissolving 5g of PVA powder in 45mL of ultrapure water and stirring at 90℃ for 3 hours with a magnetic stirrer until completely dissolved, followed by degassing and refrigeration.

[0038] The CS solution is prepared by dissolving 1g of chitosan powder in 49mL of 1% (v / v) glacial acetic acid solution, stirring at 40℃ for 6 hours with a magnetic stirrer until completely dissolved, and then degassed and refrigerated.

[0039] Example 1 Preparation of polydopamine / titanium carbide composite material (PDA / Ti3C2) (1) Preparation of polydopamine (PDA): 100 mg of dopamine hydrochloride (DA·HCl) was weighed and added to 100 mL of 10 mM Tris buffer. The mixture was stirred continuously at room temperature for 24 h to achieve the self-polymerization of dopamine. The resulting polydopamine suspension was then washed once with ultrapure water at 7000 rpm, and then washed twice with ethanol. After centrifugation, the suspension was freeze-dried in a vacuum freeze dryer at -70℃ for 24 h to obtain black PDA powder. (2) Preparation of titanium carbide (Ti3C2): In a polytetrafluoroethylene container, Ti3AlC2 was divided into two equal parts (1g each) and slowly added to 40mL of HF solution with a mass concentration of 40% at 20min intervals. During this process, the polytetrafluoroethylene container was kept in an ice bath to prevent overheating and oxidation. Then the reaction container was transferred to a water bath at 35℃ and stirred for 24h for etching. After etching, the obtained multilayer Ti3C2 suspension was washed with ultrapure water at 3500rpm until the pH value of the multilayer Ti3C2 suspension was neutral. After centrifugation and dehydration, it was transferred to a vacuum drying oven for freeze drying for 24h to obtain dark black Ti3C2 powder. (3) Preparation of polydopamine titanium carbide composite material (PDA / Ti3C2): 200 mg of Ti3C2 prepared in step (2) was added to 100 mL of 20 mM Tris buffer, and then 200 mg of DA·HCl was added. The mixture was stirred continuously at room temperature for 24 h to achieve oxidative self-polymerization of PDA on the surface of Ti3C2. After the oxidative self-polymerization was completed, the mixture was washed twice with ultrapure water at 8000 rpm, and then centrifuged and dehydrated. The mixture was then transferred to a vacuum drying oven and freeze-dried for 24 h to obtain dark black PDA / Ti3C2 powder, denoted as PT.

[0040] Example 2 Preparation of exfoliated bentonite BTex: 6.0 g of bentonite BT was added to anhydrous ethanol / ultrapure water mixture (600 mL in total, with anhydrous ethanol accounting for 20% by volume), and then stirred under microwave heating at 70 °C for 0.5 h to obtain a suspension; the obtained suspension was ultrasonically dispersed at 600 W for 1 h, stirred at 25 °C for 4 h, washed 3 times with ultrapure water, and dried in an incubator at 65 °C for 6 h to obtain exfoliated bentonite, denoted as BTex.

[0041] Example 3 A Ti3C2-based solar interface evaporator (PTB-PC) consists of an upper photothermal evaporation layer with vertically arranged pores and a base layer with a disordered porous structure. The photothermal evaporation layer contains a polydopamine / Ti3C2 composite material, and the base layer contains exfoliated bentonite. The matrix materials of both the photothermal evaporation layer and the base layer are polyvinyl alcohol / chitosan composite hydrogels.

[0042] The process diagram of the above-mentioned Ti3C2-based solar interfacial evaporator (PTB-PC) is shown in the figure. Figure 3 The specific steps are as follows: Weigh 1.75 g of 2 wt% CS solution into a 25 mL beaker, then add 5 mL of 15 mg / mL PDA / Ti3C2 suspension, sonicate for 10 min, and stir for 20 min. After stirring, add 1.5 g of 5 wt% PVA solution and stir for 20 min to obtain solution A. Weigh 1.75 g of 2 wt% CS solution into a 25 mL beaker, then add 5 mL of 15 mg / mL BTex exfoliated bentonite suspension, sonicate for 10 min, and stir for 20 min. After stirring, add 1.5 g of 5 wt% PVA solution and stir for 20 min to obtain solution B. Add 450 µL of GA to solution A, stir for 10 s, and then quickly transfer the resulting mixture. The material was placed in a freezing mold (the bottom of the freezing mold was made of copper plate and the sides were made of polytetrafluoroethylene) and gelled in situ for 10 min to obtain PT-PC gel material (denoted as PT-PC). 450 µL of GA was added to solution B and stirred for 10 s. The resulting mixture was then quickly transferred to a directional freezing mold containing the above-mentioned PT-PC gel material. The directional freezing mold was then placed in an ultra-low temperature freezer (-80℃) for 30 min. After freezing, the directional freezing mold was transferred to a vacuum freeze dryer and freeze-dried at -70℃ for 24 h to form B-PC gel material (denoted as B-PC) on the surface of the PT-PC gel material. The PT-PC gel material and the B-PC gel material together form a Ti3C2-based solar interface evaporator, denoted as PTB-PC gel evaporator.

[0043] Comparative Example 1 A method for preparing P-PC gel, the specific steps of which are as follows: Weigh 1.75 g of CS solution with a concentration of 2 wt% into a 25 mL beaker, then add 5 mL of PDA suspension with a concentration of 15 mg / mL, sonicate for 10 min, and stir for 20 min. After stirring, add 1.5 g of PVA solution with a concentration of 5 wt%, and stir for 20 min to obtain a mixture. Add 450 µL of GA to the obtained mixture, stir for 10 s, and then quickly transfer the obtained mixture into a freezing mold (the bottom of the freezing mold is a copper plate and the sides are polytetrafluoroethylene), freeze in an ultra-low temperature freezer (-80℃) for 30 min. After freezing, transfer to a vacuum freeze dryer and freeze dry at -70℃ for 24 h to obtain P-PC gel.

[0044] Comparative Example 2 A method for preparing T-PC gel, the specific steps of which are as follows: Weigh 1.75 g of 2 wt% CS solution into a 25 mL beaker, add 5 mL of 15 mg / mL Ti3C2 suspension to the beaker, sonicate for 10 min and stir for 20 min, then add 3.5 g of 5 wt% PVA solution and stir for 20 min, then add 450 µL of 40 wt% GA and stir for 10 min. Then transfer the mixture to a freezing mold (the bottom of the freezing mold is a copper plate and the sides are polytetrafluoroethylene) and freeze in an ultra-low temperature freezer (-80℃) for 30 min. After freezing, transfer it to a vacuum freeze dryer and freeze dry at -70℃ for 24 h to obtain T-PC gel.

[0045] Comparative Example 3 A method for preparing PC gel, comprising the following steps: Weigh 1.75 g of 2 wt% CS solution into a 25 mL beaker, add 3.5 g of 5 wt% PVA solution to the beaker, stir for 20 min, then add 450 µL of 40 wt% GA, stir for 10 min, then transfer the mixture to a freezing mold (the bottom of the freezing mold is a copper plate and the sides are polytetrafluoroethylene), freeze in an ultra-low temperature freezer (-80℃) for 30 min, after freezing, transfer to a vacuum freeze dryer, freeze dry at -70℃ for 24 h to obtain PC gel.

[0046] 1. Characterization and Testing (1) X-ray diffraction (XRD) X-ray diffraction was used to determine the phase and crystalline phase of solid materials, and the phase was determined by comparing the diffraction peaks with standard cards. The sample was laid flat and compacted on the sample stage and placed in the instrument's test chamber for testing. The test angle was 5°~85°, and the scanning speed was 8° / min.

[0047] (2) Scanning electron microscope (SEM) The microstructure of the samples was analyzed by scanning electron microscopy (SEM), and the elemental distribution and content on the sample surface were characterized by X-ray energy scattering spectroscopy (EDS) that is compatible with SEM.

[0048] (3) Fourier transform infrared spectroscopy (FT-IR) The functional bonds of the sample were characterized using Fourier transform infrared (FT-IR) spectroscopy, with a spectral wavelength range of 400–4000 cm⁻¹. -1 The scanning rate is 0.6 cm / s.

[0049] (4) X-ray photoelectron spectroscopy (XPS) The surface elemental composition and chemical state of the obtained material samples were characterized and analyzed by X-ray photoelectron spectroscopy (XPS, ESCALAB250Xi). The X-ray source was Al Kα (hv=1486.6eV), and the pressure inside the analysis chamber was 5×10⁻⁶. -9 Pa, the measured radiation angle is 30°.

[0050] (5) Contact angle test The hydrophilicity of the samples and the water absorption rate of different sample structures were tested using a ZJ-7000 water contact angle meter.

[0051] (6) Differential Scanning Calorimetry (DSC) The differential scanning calorimeter (DSC) of model DSC3 was used for testing. Before the test, the PTB-PC gel evaporator was placed in ultrapure water for 30 minutes to swell. The differential scanning calorimeter was then used to test the swollen sample.

[0052] (7) Thermogravimetric analysis (TGA) The obtained material was heated in air using a thermogravimetric analyzer (TGA2), and the stability of the material was determined by measuring the change in its mass.

[0053] (8) Ultraviolet-Visible-NearInfrared Diffuse Reflectance Spectrum The absorbance of the sample was measured using a UV-Vis-NIR diffuse reflectance spectrophotometer with an integrating sphere to evaluate its light absorption capacity. The model was UV-3600Plus, and the test wavelength range was 200–2600 cm⁻¹. -1 .

[0054] (9) Surface temperature test The surface temperature during the evaporation process was measured using a handheld infrared thermal imager (HM-TPMG-CY) and analyzed using HIKMICRO Analyzer software.

[0055] (10) Photothermal evaporation performance test See the physical image of the equipment used for testing photothermal evaporation performance. Figure 4 The specific testing process was as follows: Under laboratory conditions, a CME-Xe 300F solar simulator (Zhongke Micro Energy (Beijing) Technology Co., Ltd.) equipped with a standard AM 1.5G spectral filter was used to simulate actual solar irradiance (1 sun = 1 kW·m²). -2While adjusting the height of the sample stage, the light intensity was measured using an SM206E-SOLAR solar radiation meter. The PTB-PC gel evaporator prepared in Example 3 was fully swollen, cut, and polished to obtain a 2cm × 2cm × 2.5cm cube (overall effective height 1.25cm, projected area approximately 4.0cm²). -2 In the solar-driven photothermal evaporation performance and water purification tests, a cubic block was placed in a quartz test mold, with the bottom (i.e., the B-PC layer) immersed in water and the upper surface vertically irradiated by a simulated solar light source. The quartz test mold was circular and could support a white acrylic plate with square openings (the openings had a side length of 2 cm). Four circular interfaces were distributed on the side of the mold, extending into the interior. During the photothermal evaporation test, the PTB-PC gel evaporator prepared in Example 3 was placed on a perforated foam floating plate and passed through the perforated white acrylic plate (to control the vertical light absorption area).

[0056] The mass change of water evaporation in the solar thermal evaporation test was measured using a precision electronic balance (with a test accuracy of 1 mg). The balance was connected to a computer to record the mass change of water during the evaporation process in real time. All solar-driven solar thermal evaporation performance tests were conducted in an environment of 25±5℃ and 50±5% relative humidity.

[0057] 2. Results 2.1 Characterization of PTB-PC Gel Evaporator Figure 5 Figure 5 shows a 3D model diagram (a) of the PTB-PC gel evaporator provided by this invention and a physical image (b) of the PTB-PC gel evaporator prepared in Example 3. In part (b), the left side view is a side view, and the right side view is a top view. As can be seen from part (a) of Figure 5, the PTB-PC gel evaporator constructed by this invention simultaneously possesses a vertical pore structure and a disordered porous structure. As can be seen from part (b) of Figure 5, the overall length and width of the PTB-PC gel evaporator prepared in Example 3 are both 2 cm, and the height is 2.5 cm. Therefore, the area vertically receiving simulated solar radiation during the evaporation process is approximately 4 cm². -2 The lower yellow part of the PTB-PC gel evaporator is a B-PC gel base layer with added BTex, which provides support and insulation. The upper black part is a PT-PC gel photothermal evaporation layer with added PDA / Ti3C2 photothermal material, which is the main area where the water evaporation process of the evaporator occurs.

[0058] Figure 6The images show scanning electron microscope (SEM) images of the PT-PC gel material and B-PC gel material in the PTB-PC gel evaporator prepared in Example 3. (a) and (b) are PT-PC gel materials, (c) and (d) are B-PC gel materials, with (a) and (c) being 500 μm and (b) and (d) being 100 μm. Figure 6 As can be seen from parts (a) and (b), the PT-PC gel material has a neatly arranged vertical pore structure inside, which can help water to be transported from bottom to top through capillary force, which is beneficial to the mass transfer process of water and salt inside the evaporator. From Figure 6 As can be seen from parts (c) and (d) in the figure, the B-PC gel material has a disordered porous structure inside.

[0059] Figure 7 The images show scanning electron microscope (SEM) images, elemental spectra, and EDS spectra of the PT-PC gel material inside the PTB-PC gel evaporator prepared in Example 3. In the images, (a) is a scanning electron microscope image, (b) to (e) are elemental spectra of C, N, Si, and Ti, respectively, and (f) is an EDS spectrum. The inset shows the elemental content. Figure 7 The results show that C, N, Si and Ti elements are uniformly distributed inside the PT-PC gel material, and the element distribution is arranged along the pore wall, which confirms that the material is squeezed to the pore wall by ice crystals during the preparation of gel material by the ice crystal template method.

[0060] Figure 8 The images show scanning electron microscope (SEM) images, elemental spectra, and EDS spectra of the B-PC gel material inside the PTB-PC gel evaporator prepared in Example 3. In the images, (a) is a scanning electron microscope image, (b) to (e) are elemental spectra of C, N, Si, and Ti, respectively, and (f) is an EDS spectrum. The inset shows the elemental content. Figure 8 The results show that the B-PC gel material contains uniformly distributed elements such as C, N, Si and Ti, and the elements are randomly distributed.

[0061] Figure 9 XRD patterns of PC, BTex, and B-PC (a); XRD patterns of PC, P-PC, T-PC, and PT-PC (b); FT-IR spectra of PC, T-PC, P-PC, and PT-PC (c); and FT-IR spectra of PC, BTex, and B-PC (d~e). Figure 9As shown in section (a), the XRD pattern of PC exhibits the broad peaks typical of amorphous polymers, while the peak shape of BTex matches the card for montmorillonite, the main component of bentonite (MMT-PDF#42-0619), and sharp SiO2 crystallization peaks can be observed. The XRD pattern of the PC gel composited with BTex (B-PC) also matches the MMT-PDF#42-0619 card, indicating that the composite process does not alter the crystal structure of montmorillonite and SiO2 exfoliated from the bentonite. Figure 9 As shown in section (b), the amorphous peaks of P-PC indicate its characteristics as an organic polymer. Additionally, the characteristic diffraction peaks of T-PC at 9.1°, 18.4°, 34.5°, and 60.6° correspond to the (002), (004), (104), and (110) crystal planes of Ti3AlC2 (Ti3AlC2-PDF#52-0875), respectively. The characteristic diffraction peaks of PT-PC are basically consistent with those of T-PC, indicating that the PDA coating loading and PC gel bonding did not affect the crystal properties of Ti3C2MXene. Figure 9 As shown in sections (c) to (e), the wavenumber range is 3000–3700 cm⁻¹. -1 The broad peak inside and 1600cm -1 The characteristic peaks at the wavenumbers can all be attributed to the stretching vibrations of the HOH groups in H2O molecules adsorbed on the material surface, indicating that BTex, PC, and B-PC possess good hydrophilicity. Furthermore, a peak at 1042 cm⁻¹ can be observed in the FT-IR spectra of BTex and B-PC. -1 With 473cm -1 The characteristic peaks are attributed to the stretching vibrations of Si-O-Si and Si-O-Al bonds, respectively, with the characteristic peaks in BTex being more pronounced. This is because the Si-O-Si and Si-O-Al bonds originate from the silicon-oxygen tetrahedra and aluminum-oxygen octahedra of montmorillonite. Notably, the characteristic peak at 845 cm⁻¹ in the FT-IR spectrum of BTex is... -1 The characteristic peak at the wavenumber can be attributed to the Al-O bond, which shifts to 835 cm⁻¹ after BTex binds to PC. -1 This is due to the cross-linking of BTex with PC, which enhances the structural stability of the PC gel substrate. The infrared characteristic peaks of T-PC, P-PC, and PT-PC can also be observed in the wavenumber range of 3000–3700 cm⁻¹. -1 The broad peak inside and 1600cm -1The characteristic peaks at the wavenumber indicate that T-PC, P-PC, and PT-PC all possess good hydrophilicity, which is beneficial for the mass transfer of water during evaporation. Furthermore, T-PC, P-PC, and PT-PC exhibit similar characteristic peaks, and there are no obvious characteristic peaks originating from PDA and Ti3C2. This is because the infrared characteristic peaks of PDA are similar to those of PC, while the peak intensity corresponding to the Ti-C characteristic peak of Ti3C2 is relatively weak.

[0062] Figure 10 XPS total spectrum (a) and C 1s spectrum (b), O 1s spectrum (c), and Ti2p spectrum (d) for PC, T-PC, P-PC, and PT-PC. Figure 10 Part (a) confirms the elemental composition of each material. PT-PC shows a distinct Ti 2p characteristic peak at 458–464 eV, while T-PC, P-PC, and pure PC contain only C and O elemental signals, preliminarily indicating that the Ti component has been successfully introduced into the modified system. Figure 10 As shown in section (b), all samples contain CC / C=C, CO, and C=O functional groups, and the proportion of the CO peak in PT-PC is significantly increased, reflecting the enrichment of oxygen-containing functional groups on the surface of the modified material. Figure 10 As shown in section (c), PT-PC exhibits a new Ti-O bonding characteristic peak at 532.9 eV, directly demonstrating that Ti species have formed chemical bonds with the matrix. Simultaneously, the increased proportion of CO components also indicates an increase in hydrophilic sites on the material surface. Figure 10 As shown in section (d), PT-PC exhibits Ti 2p at 458.5 eV and 464.2 eV, respectively. 3 / 2 With Ti 2p 1 / 2 The characteristic bimodal pattern and spin-orbit splitting value of approximately 5.7 eV indicate that Ti is mainly distributed as Ti. 4+ The oxidation state remains stable. In summary, XPS results confirm that Ti was successfully doped and formed chemical bonds with the matrix, and the surface chemical environment and functional group distribution of the modified sample were effectively optimized.

[0063] Figure 11 XPS total spectra of PC, BT, and B-PC (a), and C 1s (b), Al 2p (c), O 1s (d), and N 1s (e) spectra of PC, BTex, and B-PC. Figure 11 As shown in section (a), PC only exhibits characteristic peaks for C and O elements, while B-PC simultaneously detects Al 2p, N 1s, and enhanced O 1s signals, indicating that BTex was successfully introduced into the PC matrix and altered its surface elemental distribution. Figure 11As shown in section (b), all samples contain three functional groups: CC / C=C, CO / CN, and C=O. The CO / CN peak proportion of B-PC is significantly increased, while the C=O peak shows a slight shift, reflecting the interfacial interaction between BT and PC. Figure 11 As shown in section (c), PC shows no Al signal, BTex contains only Al-O bonds, while B-PC exhibits both Al-OC and Al-O bonds, proving that Al forms new chemical bonds with the PC matrix. Figure 11 As shown in section (d), B-PC incorporates Al-OC, HOC, and lattice O components, resulting in a more complex oxidation environment. For example... Figure 11 As shown in section (e), B-PC retains the characteristic peaks of RC=N and -NH2, and also exhibits the -NSiO2 component, indicating that nitrogen participates in the interfacial bonding process. In summary, the XPS results show that the introduction of BTex not only successfully doped Al and N elements, but also formed new chemical bonding structures through interfacial reactions, optimizing the chemical environment of the material surface.

[0064] The photothermal conversion capability and thermal positioning capability of the evaporator are extremely important for the overall energy utilization efficiency and can significantly improve the photothermal evaporation rate. By comparing the temperature rise of PT-PC, B-PC and PTB-PC under one solar irradiance, the thermal positioning capability of the PTB-PC gel evaporator was demonstrated.

[0065] Figure 12 The graphs show the surface temperatures of the PTB-PC gel evaporator prepared in Example 3 under dry conditions and without light (a), the surface temperatures of the PT-PC gel material prepared in Example 3 under dry conditions and with one solar irradiance (b), the surface temperatures of the PTB-PC gel evaporator prepared in Example 3 under dry conditions and with one solar irradiance (c), and the corresponding 3D temperature distribution maps (d~f). In the graphs, (d) is the 3D temperature distribution map of (a), (e) is the 3D temperature distribution map of (b), and (f) is the 3D temperature distribution map of (c). White labels represent the center temperature, blue labels represent the lowest temperature, and red labels represent the highest temperature. Figure 12 As can be seen in section (a), the surface temperature of the PTB-PC gel evaporator is 24.7℃ at an ambient temperature of 26.0℃, which is lower than the ambient temperature. This is because the PT-PC gel material has excellent hydrophilicity, enabling it to absorb water from the air and achieve cooling. Figure 12 As shown in section (b), the surface temperature of the PT-PC gel material stabilizes at 85.7℃ after 15 minutes of simulated sunlight irradiation (1 Sun), indicating that the PT-PC gel material possesses excellent photothermal conversion capabilities. Figure 12As can be seen in section (c), after further increasing the B-PC gel substrate layer, the PTB-PC gel evaporator can achieve a surface temperature of 90.4℃ under simulated sunlight with an intensity of 1 Sun irradiation. This indicates that the thermal insulation design of B-PC reduces the process of heat conduction downward from the PT-PC gel photothermal layer.

[0066] Figure 13 Infrared thermal images showing the surface temperature changes over time of the PT-PC gel material and PTB-PC gel evaporator prepared in Example 3 under wet conditions and with one solar irradiance, where (a) is the PT-PC gel material and (b) is the PTB-PC gel evaporator. Figure 13 It can be seen that, compared with PT-PC gel material, PTB-PC gel evaporator achieved a higher surface temperature, which can be stabilized at 42.7℃. This indicates that by constructing a B-PC gel thermal insulation substrate, PTB-PC gel evaporator has excellent thermal positioning capability, which helps to improve the evaporation efficiency of gel evaporator during the evaporation process.

[0067] Figure 14 Infrared thermal images of the side temperature of the PTB-PC gel evaporator prepared in Example 3 under wet conditions and with 1 solar irradiance, showing the time changes over time, from left to right: 0 minutes, 1 minute, and 60 minutes. Figure 14 It can be seen that during the evaporation process, the heating interface of the PTB-PC gel evaporator is clearly concentrated. When the evaporation interface heats up to about 40°C, the B-PC gel portion remains at around 22°C, even lower than the water temperature. This demonstrates that, on the one hand, the thermal positioning capability of the PTB-PC gel evaporator makes it difficult for heat to be lost through the water transfer process; on the other hand, it helps the gel absorb heat from the environment, thereby exceeding the upper limit of energy conversion.

[0068] In the process of interfacial solar thermal evaporation, providing sufficient moisture to the evaporation interface is one of the key factors for improving the performance of solar thermal evaporation. The key to providing sufficient moisture lies in the water transport capacity and hydrophilicity of the evaporator material. Different gel internal structures determine the water mass transfer pathways and rates, thus having different impacts on the moisture supply process at the evaporation interface.

[0069] Figure 15 The hydrophilicity of the PT-PC gel material prepared in Example 3 is shown in (a), the hydrophilicity of the B-PC gel material is shown in (b), the internal pore structure of the PT-PC gel material is shown in (c), and the internal pore structure of the B-PC gel material is shown in (d). Figure 15As shown in sections (a) and (b), due to the loose and porous structure of the PC gel substrate and the hydrophilicity of PDA / Ti3C2 and BT, both PT-PC gel materials and B-PC gel materials can absorb water droplets within 0.7 s. This indicates that both PT-PC gel materials and B-PC gel materials have good hydrophilicity. Furthermore, compared to the B-PC gel material which requires 0.68 s to absorb a water droplet, the PT-PC gel material has a faster water absorption capacity, absorbing water droplets within 0.33 s. This may be due to the enhanced water transport capacity caused by the internal capillary force of the vertical pore structure.

[0070] The evaporation stability of gel evaporators in long-term aquatic environments reflects their continuous evaporation performance in practical applications and is an important criterion for evaluating their practical application potential. Figure 16 The long-term evaporation stability of the PTB-PC gel evaporator prepared in Example 3 under one solar irradiance intensity. From Figure 16 It can be seen that after 7 days of cycling, the PTB-PC gel evaporator can still maintain a high water evaporation efficiency without significant efficiency decline.

[0071] The PTB-PC gel evaporator prepared in Example 3 was immersed in tap water for 7 days. The state of the tap water in the beaker and the PTB-PC gel evaporator were observed. The results are shown below. Figure 17 .

[0072] Figure 17 The stability of the PTB-PC gel evaporator prepared in Example 3 in water is shown, where (a) is immersion for 0 days and (b) is immersion for 7 days. Figure 17 It can be seen that the tap water in the beaker did not change significantly, and the overall structure of the PTB-PC gel evaporator remained intact, indicating that the PTB-PC gel evaporator has long-term stability in water. This is due to the enhancing effect of PDA / Ti3C2 and BTex on the gel structure.

[0073] A 10 wt% NaCl solution was used as simulated seawater for seawater desalination experiments. The PTB-PC gel evaporator prepared in Example 3 was continuously immersed in the NaCl solution for 5 hours. The state of the NaCl solution and the PTB-PC gel evaporator was observed, and the results are shown in [the table below]. Figure 18 .

[0074] Figure 18 The image shows the PTB-PC gel evaporator prepared in Example 3 after being continuously immersed in a 10 wt% NaCl solution for 5 hours. (From...) Figure 18As can be seen, no obvious salt crystallization was observed on the surface of the PTB-PC gel evaporator during the continuous 5-hour seawater desalination experiment, demonstrating high stability. This may be due to the specific vertical pore structure and good hydrophilicity of the PT-PC photothermal evaporation layer, which can supply water to the evaporation interface in a timely manner.

[0075] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A Ti3C2-based solar interface evaporator, characterized in that, The Ti3C2-based solar interface evaporator consists of a photothermal evaporation layer with vertically arranged pores and a substrate layer with a disordered porous structure. The photothermal evaporation layer contains a polydopamine / Ti3C2 composite material; the base layer contains bentonite; and the matrix material of both the photothermal evaporation layer and the base layer is a polyvinyl alcohol / chitosan composite hydrogel.

2. The Ti3C2-based solar interface evaporator according to claim 1, characterized in that, The photothermal evaporation layer is prepared by ice crystal template method using polydopamine / Ti3C2 composite material, chitosan, polyvinyl alcohol and crosslinking agent.

3. The Ti3C2-based solar interface evaporator according to claim 1, characterized in that, The base layer is prepared by freeze casting of bentonite, chitosan, polyvinyl alcohol and crosslinking agent.

4. The Ti3C2-based solar interface evaporator according to claim 1, characterized in that, The preparation method of the polydopamine / Ti3C2 composite material includes: adding dopamine hydrochloride to a Ti3C2 solution for oxidative self-polymerization, and then washing, dehydrating and drying to obtain the polydopamine / Ti3C2 composite material.

5. A method for preparing a Ti3C2-based solar interfacial evaporator as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Add polydopamine / Ti3C2 composite material suspension to chitosan solution, mix well, then add polyvinyl alcohol solution and stir to obtain solution A; add bentonite suspension to chitosan solution, mix well, then add polyvinyl alcohol solution and stir to obtain solution B. A crosslinking agent is added to solution A, and the resulting mixture A is then transferred to a mold for in-situ gelation to obtain a polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material. A crosslinking agent is added to solution B, and the resulting mixture B is then transferred to a mold containing the polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material. The mixture is then subjected to ultra-low temperature freezing and freeze-drying to form a bentonite-polyvinyl alcohol / chitosan gel material on the surface of the polydopamine / Ti3C2-polyvinyl alcohol / chitosan gel material, thus obtaining the Ti3C2-based solar interface evaporator.

6. The preparation method according to claim 5, characterized in that, In solutions A and B, the ratio of chitosan solution, polydopamine / Ti3C2 composite material suspension or bentonite and polyvinyl alcohol solution is 1.75g:5mL:1.5g.

7. The preparation method according to claim 6, characterized in that, In solutions A and B, the concentration of chitosan solution is 2 wt%, the concentration of polydopamine / Ti3C2 composite material suspension is 15 mg / mL, and the concentration of polyvinyl alcohol solution is 5 wt%.

8. The preparation method according to claim 5, characterized in that, The in-situ gelation temperature was room temperature, and the in-situ gelation time was 10 minutes.

9. The preparation method according to claim 5, characterized in that, The ultra-low temperature freezing temperature is -80℃, and the ultra-low temperature freezing time is 30 minutes.

10. The application of a Ti3C2-based solar interface evaporator as described in any one of claims 1 to 4 in the production of clean water.

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