Preparation of a bimetallic MXene composite membrane material and application thereof in photothermal water evaporation

Abstract

A preparation method of a bimetallic MXene photothermal composite film material. By controlling the ratio of metal powder (V, Nb and Al) and graphite, MAX phase NbVAlC powder is prepared by high temperature sintering in a vacuum tube furnace, and then the Al atomic layer in NbVAlC is etched by acid solution etching method to obtain NbVCT x MXene powder, and by adding polyethyleneimine (PEI) modification, dopamine (DA) modification self-assembly to obtain P-NbVCT x , and then vacuum filtration to PVDF film to obtain nP-NbVCT x photothermal composite film. The P-NbVCT x material structure in the application is combined stably, the nP-NbVCT x composite film has good photothermal conversion effect, and shows excellent water evaporation performance in solar photothermal water evaporation, the water evaporation rate under 1 solar irradiation is as high as 3.20 kg·m ‑2 ·h ‑1 , and the water evaporation efficiency is as high as 98.9%. Meanwhile, the preparation method of the bimetallic NbVCT x material in the application is simple, short in time period and high in success rate, and has strong industrial application prospect in photothermal water evaporation film material.

Description

Technical Field

[0001] This invention belongs to the field of solar photovoltaic water evaporation technology, specifically relating to a method for preparing a bimetallic MXene composite film material. Background Technology

[0002] In recent years, one of the effective strategies for solving the problem of freshwater scarcity has been the use of solar-driven interfacial water evaporation technology. This technology uses solar energy as a light source and seawater as a water source, obtaining light and heat from solar radiation. The energy is then converted in a photothermal conversion material, resulting in water evaporation at the seawater interface. The condensate is then collected as freshwater. This effectively utilizes the entire solar spectrum, yields high-quality collected freshwater, and offers advantages such as high efficiency, low carbon footprint, and environmental friendliness. For solar photothermal water evaporation, excellent photothermal conversion materials and efficient thermal management determine its usability. MXenes, as a novel two-dimensional transition metal carbonitride, exhibit significant localized surface plasmon resonance effects and a wide light absorption range, demonstrating excellent photothermal conversion performance. Furthermore, the active surface chemical groups of MXenes make them easy to combine and modify with other materials to form photothermal conversion composite materials with even better performance.

[0003] Currently, most research and applications of MXene photothermal conversion focus on Ti3C2T. x While there are few reports on bimetallic MXenes and their composites, the synthesis of various MXene composite films and the study of their photothermal conversion performance are of great significance. Bimetallic MXenes possess a unique structure compared to monometallic MXenes. The composition of bimetallic MXenes can be rationally controlled, structurally optimized, and the surface functional groups designed to further regulate their light absorption, especially the selective absorption of specific wavelengths. This provides a vast space for the structural design of photothermal conversion materials requiring broad-spectrum absorption. Bimetallic MXene materials can achieve precise control over light absorption through changes in composition and atomic structure, thereby enhancing their conductivity, charge storage capacity, and photothermal conversion capabilities. However, the complexity of the synthesis of bimetallic MAX phases and the variability of bond energies in the MXene etching process remain pressing issues to be addressed.

[0004] To address the aforementioned technical problems, this invention provides NbVCT x MXene was explored through bimetallic NbVCT. xThis paper analyzes the application of bimetallic MXene in solar photothermal evaporation films, aiming to provide application value for the field of photothermal evaporation technology. The study of photothermal evaporation films revealed that the surface structure and photothermal transport channels of the photothermal composite film are relatively weak, which reduces the photothermal conversion performance of the film material. Meanwhile, bimetallic NbVCT... x MXene also suffers from poor stability in water / oxygen environments, hindering its practical application. Therefore, surface modification by combining it with organic or inorganic materials to prepare MXene composites can improve the stability of MXene, thereby enhancing the overall photothermal conversion capability of the composite material. This invention prepares bimetallic NbVCT by sintering the NbVAlC MAX phase and then acid etching it. x MXene was used to prepare P-NbVCT through self-assembly by adding polyethyleneimine (PEI) and dopamine (DA). x The composite material was then vacuum filtered onto a PVDF membrane to obtain nP-NbVCT. x Composite membrane. Finally, the prepared nP-NbVCT x The photothermal conversion effect of composite materials was studied, and their application in photothermal evaporation membranes yielded excellent water evaporation results. This research on the water evaporation performance of bimetallic MXene materials provides a novel strategy and solution with practical significance for solar photothermal evaporation seawater desalination technology. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation. The aim is to solve the problem of low light absorption and photothermal conversion efficiency of bimetallic MXene as a photothermal evaporation material, thereby improving the evaporation rate of solar photothermal water and providing a simple and practical photothermal material preparation scheme. The bimetallic MXene material NbVCT in this invention... x The preparation method is simple, the etching effect is excellent, and nP-NbVCT x The composite membrane has a stable structure, a fast photothermal evaporation rate, and a high photothermal conversion efficiency, making it highly valuable for future applications in solar photothermal evaporation membranes.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The preparation of a bimetallic MXene composite membrane material and its application in photothermal evaporation include the following steps:

[0008] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 2-4 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1400-1600℃ for 2-4 hours with a heating rate of 5-10℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0009] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0 g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20 ml of 9 mol / L acid solution. Etch the solution in a 40°C constant-temperature water bath with magnetic stirring for 24–72 h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 0.5–1 h, and finally centrifuge at 6000 rpm for 10 min. Collect the supernatant and freeze-dry for 48 h to obtain NbVCT. x powder;

[0010] (3) P-NbVCT was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) addition. x Composite material: First, a 10 mg / ml NbVCT solution was prepared. x The dispersion was modified by adding PEI to the dispersion for amination, followed by the dropwise addition of DA solution, and NbVCT was continuously stirred. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0011] (4) nP-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was slowly added dropwise onto polytetrafluoroethylene filter paper, followed by vacuum filtration to obtain an MXene composite membrane. Finally, the composite membrane was vacuum dried to remove moisture. Different masses of P-NbVCT were weighed... x Powder n can yield P-NbVCT with different mass fractions. x The composite membrane is denoted as nP-NbVCT. x Composite membrane;

[0012] (5) Solar photothermal water evaporation experiment using a xenon lamp light source: The nP-NbVCTx composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below to record real-time water mass loss. An AM 1.5G filter was configured for solar radiation, the light intensity was controlled by adjusting the light source current, and the illumination range was adjusted so that the light shone perpendicularly onto the surface of the composite membrane. The changes in the balance reading were recorded at regular intervals, and the temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0013] Preferably, in the preparation of NbVAlC MAX phase powder by high-temperature vacuum sintering, the NbVAlC powder obtained by grinding and sieving is 200 mesh.

[0014] Preferably, during the etching of NbVAlC powder with acid, the acid solution can be one of the strongly acidic environmental systems such as hydrofluoric acid, hydrochloric acid, sulfuric acid, or lithium fluoride-hydrochloric acid solution.

[0015] Preferably, during the acid etching process of NbVAlC powder, the time required for complete etching of the MAX phase NbVAlC powder can be 24-72 hours, and the etching temperature can be 20-40°C, so as to achieve a sufficient etching effect on the Al element in the MAX phase.

[0016] Preferably, the etching of NbVAlC to prepare NbVCT is... x During the ultrasonication of the powder, the ultrasonication time is 0.5–2 hours, the ultrasonic power is 600W, and the frequency is 40kHz. The process must be carried out in an ice-water bath, and nitrogen gas must be introduced simultaneously to prevent NbVCT. x The powder oxidized due to excessively high temperature.

[0017] Preferably, the polyethyleneimine (PEI) aminated NbVCT x The dosage can be 10-50mg, and the temperature in the constant temperature shaker is 29℃, and the shaking time is 1h.

[0018] Preferably, the addition of dopamine (DA) to modify NbVCT x The dosage can be 1-5mg, and the temperature in the constant temperature shaker is 29℃, and the shaking time is 2h.

[0019] Preferably, the preparation of nP-NbVCT x The amount of composite membrane used can be 10-100mg.

[0020] Preferably, the water used in the solar-powered photothermal evaporation process can be one of seawater, concentrated brine, or ultrapure water.

[0021] Preferably, the intensity of the light source used in the solar photothermal evaporation process is standard sunlight, and the light source surface should be able to sufficiently illuminate the nP-NbVCT. x On the composite membrane.

[0022] Preferably, in the process of using a light source for solar photothermal evaporation, it is necessary to record the water evaporation mass loss at regular intervals, and at the same time, use a thermal imager to measure the surface temperature of the composite film for water evaporation, and calculate its photothermal conversion efficiency, water evaporation rate and efficiency.

[0023] The significant advantages of this invention are:

[0024] 1. This invention utilizes high-temperature vacuum sintering to obtain structurally stable NbVAlC MAX phase powder. NbVAlC MAX phase powder is prepared by mixing and grinding metal powders (V, Nb, and Al) with graphite powder in different proportions, followed by sintering. Simultaneously, etching with an acid solution effectively removes the Al atomic layer, yielding lamellar NbVCT. x MXene powder. This method is simple, easy to operate, has a high success rate, and produces good results.

[0025] 2. In this invention, PEI is used for amination modification, and DA is used for further modification to obtain P-NbVCTx materials with stable properties and structure. The addition of PEI enables NbVCTx to... x It produces a stable adsorption effect and can prevent NbVCT. x The material undergoes oxidation; the modification of DA can produce a self-assembly effect, enabling the amination-modified NbVCT to undergo oxidation. x The material exhibits a tightly bound, ordered layered structure, and also exhibits a synergistic effect of hydrogen bonds, covalent bonds, and electrostatic interactions. The material is structurally stable and the preparation process is simple and easy to operate.

[0026] 3. nP-NbVCT in this invention x The composite membrane exhibits excellent solar thermal water evaporation performance. This is achieved by using different concentrations of NbVCT. x MXene powder was ultrasonically dispersed and vacuum filtered onto a polytetrafluoroethylene substrate to obtain P-NbVCT. x The composite membrane, wherein the MXene composite membrane has broad spectral absorption characteristics, exhibits excellent photothermal conversion capabilities, and this P-NbVCT x The composite membrane exhibits a high water evaporation rate in photothermal evaporation experiments, demonstrating strong application capabilities and promising prospects in photothermal evaporation. Attached Figure Description

[0027] Figure 1 The NbVAlC MAX phase and NbVCT prepared in this invention x XRD pattern of MXene.

[0028] Figure 2 The NbVAlC MAX phase and NbVCT prepared in this invention x Scanning electron microscope image of MXene.

[0029] Figure 3 The P-NbVCT prepared in this invention x Cross-sectional scanning electron microscope image of the composite membrane.

[0030] Figure 4 Mass change curves of different composite membranes and comparative examples during 1 hour of photothermal evaporation in the embodiments of the present invention.

[0031] Figure 5 Temperature curves of different composite membranes and comparative examples in the embodiments of the present invention. Detailed Implementation

[0032] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, specific embodiments are provided below to further illustrate the technical solution of this invention. It should be understood that the specific embodiments described herein are only for explaining this invention and are not intended to limit this invention.

[0033] Example 1

[0034] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation, characterized by the following steps:

[0035] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 3 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1400℃ for 4 hours with a heating rate of 5℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0036] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0 g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20 ml of 9 mol / L hydrochloric acid solution. Etch the solution in a 40°C constant-temperature water bath with magnetic stirring for 72 h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 0.5 h, and finally centrifuge at 6000 rpm for 10 min. Collect the supernatant and freeze-dry for 48 h to obtain NbVCT. xpowder;

[0037] (3) P-NbVCT was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) addition. x Composite material: First, a 10 mg / mL NbVCT solution was prepared. x The dispersion was modified by adding 10 mg of PEI to the dispersion for amination, followed by the dropwise addition of 1 mg of DA solution, while continuously stirring to allow NbVCT to react. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0038] (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain the MXene composite membrane. 10 mg of NbVCTx powder was weighed and labeled as 10P-NbVCTx photothermal membrane. Finally, the composite membrane was freeze-dried in a freeze dryer to remove moisture.

[0039] (5) Solar photothermal evaporation experiment using xenon lamp light source: 10P-NbVCT x A composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below it to record real-time water mass loss. The intensity of the light source, sunlight (1 Sun = 1000 W·m), was adjusted. -2 The surface of the composite membrane was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0040] 10P-NbVCT obtained x After a 1-hour water evaporation experiment, the composite membrane surface temperature reached a maximum of 40.9℃, and the water evaporation rate was 2.26 kg·m³. -2 ·h -1 .

[0041] Example 2

[0042] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation, characterized by the following steps:

[0043] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 3 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1500℃ for 4 hours with a heating rate of 5℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0044] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0 g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20 ml of sulfuric acid solution. Etch the powder using magnetic stirring in a 40°C constant-temperature water bath for 72 h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 0.5 h, and finally centrifuge at 6000 rpm for 10 min. Collect the supernatant and freeze-dry for 48 h to obtain NbVCT. x powder;

[0045] (3) P-NbVCTx composite material was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) modification: First, 10 mg / mL NbVCT was prepared. x The dispersion was modified by adding 20 mg of PEI to the dispersion for amination, followed by the dropwise addition of 2 mg of DA solution, while continuously stirring to allow NbVCT to react. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0046] (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain the MXene composite membrane. 20 mg of NbVCTx powder was weighed and labeled as 20P-NbVCTx photothermal film. Finally, the composite membrane was freeze-dried in a freeze dryer to remove moisture.

[0047] (5) Solar photothermal evaporation experiment using xenon lamp light source: 20P-NbVCT x A composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below it to record real-time water mass loss. The intensity of the light source, sunlight (1 Sun = 1000 W·m), was adjusted. -2The surface of the composite membrane was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0048] 20P-NbVCT obtained x After a 1-hour water evaporation experiment, the composite membrane surface temperature reached a maximum of 42.8℃, and the water evaporation rate was 2.50 kg·m³. -2 ·h -1 .

[0049] Example 3

[0050] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation, characterized by the following steps:

[0051] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 4 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1600℃ for 3 hours with a heating rate of 5℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0052] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0 g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20 ml of 9 mol / L hydrofluoric acid solution. Etch the solution in a 40°C constant-temperature water bath with magnetic stirring for 48 h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 1 h, and finally centrifuge at 6000 rpm for 10 min. Collect the supernatant and freeze-dry for 48 h to obtain NbVCT. x powder;

[0053] (3) P-NbVCTx composite material was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) modification: First, 10 mg / mL NbVCT was prepared. x The dispersion was modified by adding 30 mg of PEI to the dispersion for amination, followed by the dropwise addition of 3 mg of DA solution, while continuously stirring to achieve NbVCT. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0054] (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCTx P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain the MXene composite membrane. 30 mg of NbVCTx powder was weighed and labeled as 30P-NbVCTx photothermal membrane. Finally, the composite membrane was freeze-dried in a freeze dryer to remove moisture.

[0055] (5) Solar photothermal evaporation experiment using xenon lamp light source: 30P-NbVCT x A composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below it to record real-time water mass loss. The intensity of the light source, sunlight (1 Sun = 1000 W·m), was adjusted. -2 The surface of the composite membrane was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0056] 30P-NbVCT obtained x After a 1-hour water evaporation experiment, the composite membrane surface temperature reached a maximum of 45.8℃, and the water evaporation rate was 2.76 kg·m³. -2 ·h -1 .

[0057] Example 4

[0058] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation, characterized by the following steps:

[0059] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 4 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1600℃ for 3 hours with a heating rate of 6℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0060] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20ml of a mixed acid solution of 1.0g lithium fluoride and 9mol / L hydrochloric acid. Etch the solution in a 40℃ constant-temperature water bath with magnetic stirring for 48h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 1h, and finally centrifuge at 6000rpm for 10min. Collect the supernatant and freeze-dry for 48h to obtain NbVCT. x powder;

[0061] (3) P-NbVCTx composite material was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) modification: First, 10 mg / mL NbVCT was prepared. x The dispersion was modified by adding 40 mg of PEI to the dispersion for amination, followed by the dropwise addition of 4 mg of DA solution, while continuously stirring to allow NbVCT to react. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0062] (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain the MXene composite membrane. 40 mg of NbVCTx powder was weighed and designated as 40P-NbVCTx photothermal film. Finally, the composite membrane was freeze-dried in a freeze dryer to remove moisture.

[0063] (5) Solar photothermal evaporation experiment using xenon lamp light source: 40P-NbVCT x A composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below it to record real-time water mass loss. The intensity of the light source, sunlight (1 Sun = 1000 W·m), was adjusted. -2 The surface of the composite membrane was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0064] 40P-NbVCT obtained x After a 1-hour water evaporation experiment, the composite membrane surface temperature reached a maximum of 46.7℃, and the water evaporation rate was 2.84 kg·m³. -2 ·h -1 .

[0065] Example 5

[0066] This invention provides a method for preparing a bimetallic MXene composite film material and its application in photothermal evaporation, characterized by the following steps:

[0067] (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: A certain amount of metal powder (V, Nb and Al) and graphite powder were weighed and mixed in an agate mortar. After manual grinding for 2 hours, the mixture was sieved. Then, the mixture was pressed into a block tablet at 15 MPa for 10 minutes. The tablet was placed in a vacuum tube furnace and sintered under an argon atmosphere. The temperature was maintained at 1400-1600℃ for 2 hours with a heating rate of 5℃ / min. The mixture was cooled with the furnace and finally ground and sieved to obtain NbVAlC powder.

[0068] (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh 1.0 g of NbVAlC powder and gradually add it to a polytetrafluoroethylene beaker containing 20 ml of 9 mol / L hydrofluoric acid. Etch the powder using magnetic stirring in a 40°C water bath for 24 h. Then, wash and centrifuge multiple times, adjusting the pH of the supernatant to approximately neutral. Next, sonicate for 0.5 h, and finally centrifuge at 6000 rpm for 10 min. Collect the supernatant and freeze-dry for 48 h to obtain NbVCT. x powder;

[0069] (3) P-NbVCTx composite material was prepared by self-assembly using polyethyleneimine (PEI) amination modification and dopamine (DA) modification: First, 10 mg / mL NbVCT was prepared. x The dispersion was modified by adding 50 mg of PEI to the dispersion for amination, followed by the dropwise addition of 5 mg of DA solution, while continuously stirring to allow NbVCT to react. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder;

[0070] (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain the MXene composite membrane. 50 mg of NbVCTx powder was weighed and labeled as 50P-NbVCTx photothermal film. Finally, the composite membrane was freeze-dried in a freeze dryer to remove moisture.

[0071] (5) Solar photothermal evaporation experiment using a xenon lamp light source: 50P-NbVCT x A composite membrane was placed on the surface of a beaker containing deionized water, and a high-precision analytical balance was placed below it to record real-time water mass loss. The intensity of the light source, sunlight (1 Sun = 1000 W·m), was adjusted.-2 The surface of the composite membrane was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite membrane were analyzed using an infrared thermal imager.

[0072] 50P-NbVCT obtained x After a 1-hour water evaporation experiment, the composite membrane surface temperature reached a maximum of 48.7℃, and the water evaporation rate was 3.20 kg·m³. -2 ·h -1 .

[0073] Comparative Example 1

[0074] A solar-powered photothermal evaporation experiment was conducted using a xenon lamp light source: a beaker containing deionized water was placed directly on a high-precision analytical balance below, and the intensity of the sunlight source was adjusted to 1 Sun (1000 W·m). -2 The surface was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite film were analyzed using an infrared thermal imager.

[0075] Comparative Example 2

[0076] A solar-powered photothermal evaporation experiment was conducted using a xenon lamp light source: A blank PVDF membrane was placed on a beaker containing deionized water, and a high-precision analytical balance was positioned below. The intensity of the sunlight source was adjusted to 1 Sun (1000 W·m²). -2 The surface was vertically illuminated, and the changes in the balance reading were recorded. The temperature changes on the surface of the composite film were analyzed using an infrared thermal imager.

[0077] Figure 1 The NbVAlC MAX phase and NbVCT prepared in this invention x XRD pattern of MXene; Figure 2 The NbVAlC MAX phase and monolayer NbVCT prepared in this invention x Scanning electron microscope image of MXene; from Figure 1 and Figure 2 It can be seen that the MAX phase prepared by high-temperature sintering has a tightly packed layered structure. By selectively removing and etching the Al layer with acid, monolayer thin sheets of NbVCT can be clearly observed. x MXene. Figure 3 P-NbVCT prepared in this invention x A cross-sectional scanning electron microscope image of the composite membrane, which can be viewed as P-NbVCT. x The composite membrane has a uniform sheet structure. Figure 4 These are the mass change curves of different MXene composite membranes and the comparative example during 1 hour of photothermal evaporation in the embodiments of the present invention. Figure 5 The surface temperature of the composite membrane shows that the modified P-NbVCT... xThe material exhibits excellent photothermal evaporation performance. After irradiation by the light source, the surface temperature of the photothermal film rises to a maximum of 49℃. As shown in Table 1, the water evaporation rate and photothermal evaporation conversion efficiency reach 3.20 kg·m³ after 1 hour. -2 ·h -1 The photothermal evaporation efficiency reached 98.9%, indicating that the bimetallic NbVCT... x MXene exhibits superior photothermal conversion capabilities.

[0078] Table 1. Water evaporation rate and photothermal evaporation efficiency of different MXene composite membranes and comparative examples in the embodiments of the present invention.

[0079]

[0080] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a bimetallic MXene photothermal composite film material, characterized in that, Includes the following steps: (1) Preparation of MAX phase NbVAlC powder by high temperature vacuum sintering: Metal powder and graphite powder were mixed in an agate mortar, ground by hand and sieved, and then pressed into block tablets by a tablet press. The tablets were placed in a vacuum tube furnace and sintered under an argon atmosphere. The furnace was kept at a high temperature for a period of time with a heating rate of 5-10℃ / min. The furnace was cooled, and finally NbVAlC powder was obtained by grinding and sieving. (2) NbVCT was prepared by direct etching with acid solution. x Powder: Weigh NbVAlC powder and gradually add it to a beaker containing acid solution. Etch the solution with magnetic stirring in a constant temperature water bath. After etching for a period of time, wash and centrifuge multiple times. Adjust the pH of the supernatant to neutral, then sonicate. Finally, collect the supernatant by high-speed centrifugation and freeze-dry to obtain NbVCT. x powder; (3) P-NbVCTx composite material was prepared by self-assembly using polyethyleneimine amination modification and dopamine addition: First, NbVCT was prepared. x The dispersion was modified by adding polyethyleneimine to it and shaking it in a constant-temperature shaker. Dopamine solution was then added dropwise while continuously stirring to achieve NbVCT. x After completing self-assembly, P-NbVCT was then subjected to... x The mixture was freeze-dried to obtain P-NbVCT. x powder; (4) P-NbVCT was prepared by vacuum filtration method. x Composite membrane: P-NbVCT x P-NbVCT was prepared by ultrasonic dispersion of powder in deionized water. x The dispersion was dropped onto polytetrafluoroethylene filter paper and then vacuum filtered to obtain an MXene composite membrane; finally, the surface moisture of the membrane was removed by vacuum drying.

2. The method according to claim 1, characterized in that: In step (1), the metal powder includes V, Nb and Al; the metal powder and graphite powder are weighed by molar ratio, and the molar ratio is Nb:V:Al:C=1:1:(1.2-1.5):

1.

3. The method according to claim 1, characterized in that: In step (1), the powder is manually ground for 2-4 hours until the particle size is uniform and then passed through a 200-mesh sieve. The amount of tablets used is 0.5g.

4. The method according to claim 1, characterized in that: In step (2), the acid solution includes any one of hydrofluoric acid, hydrochloric acid, sulfuric acid, or lithium fluoride-hydrochloric acid solution, and the etching time is 24-72h.

5. The method according to claim 1, characterized in that: In step (2), after etching, the sample is washed with deionized water and centrifuged multiple times at 6000 rpm until the pH is neutral. The ultrasonic treatment is carried out in an ice-water bath with an ultrasonic power of 600W and a frequency of 40kHz.

6. The method according to claim 1, characterized in that: In step (3), the amount of polyethyleneimine used is 10-50 mg; the amount of dopamine used is 1-5 mg.

7. The method according to claim 1, characterized in that: The amination and oscillation process in step (3) takes 0.5-3 hours, and the stirring time for adding dopamine modification is 0.5-3 hours.

8. The method according to claim 1, characterized in that, In step (4), P-NbVCT x The powder weighs 10-100 mg.

9. The application of the bimetallic MXene photothermal composite film material prepared by any one of the methods described in claims 1-8 in photothermal evaporation.

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