A method to improve the performance of MXene-based water evaporation power generation devices

Abstract

This disclosure discloses a method for improving the performance of MXene-based water evaporation power generation devices, belonging to the technical field of water evaporation power generation devices. The method comprises: mixing FeCl2·4H2O, deionized water, ascorbic acid, and ethylene glycol, and introducing nitrogen or argon to obtain an etching solution; adding carbon nanotubes to the etching solution and adjusting the pH to 4; adding MAX powder to the etching solution, performing an etching reaction, and allowing the solution to stand to obtain a supernatant; centrifuging the supernatant, washing it, and drying it to obtain a precipitate; preparing the precipitate into a solution, filtering it through filter paper, and drying it to obtain a MXene / CNT / filter paper composite film; and connecting conductive portions to the upper and lower ends of the MXene / CNT / filter paper composite film to obtain a water evaporation power generation device. The CNTs are assembled by in-situ hydroxyl radical acidification and etching, forming chemical bonds between the CNTs and the MXene film, effectively improving the current and voltage of the device.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of water evaporation power generation devices, and specifically relates to a method for improving the performance of MXene-based water evaporation power generation devices. Background Art

[0002] The development of new, clean, sustainable and widely distributed renewable energy technologies has become an urgent need for the sustainable development of human society.

[0003] Water evaporation, a key component of the water cycle (the continuous conversion of surface water in bodies of water, such as oceans, lakes, rivers, and soil, into water vapor), is a spontaneous, ubiquitous natural phenomenon driven continuously by solar energy. It is estimated that evaporation consumes approximately 60% of the incoming solar radiation (approximately 1023 J) annually on Earth's surface. Its energy flux density is significantly higher than that of other renewable energy sources, such as wind and hydropower. Therefore, water evaporation power generation technology, due to its self-driven, environmentally friendly, potentially low-cost, and miniaturizable and wearable nature, offers unique application prospects in distributed micro- and nano-energy supply (such as powering IoT sensors and wearable devices), powering off-grid areas, self-powering environmental monitoring systems, and complementing other renewable energy sources (such as solar energy).

[0004] MXene is an emerging two-dimensional inorganic material composed of transition metal carbides, nitrides, or carbonitrides. Its abundant hydrophilic functional groups (-O, -OH, -F, etc.), high specific surface area, and nanochannel structure give it great application prospects in the field of water evaporation power generation. However, there are currently few reports on MXene-based water evaporation power generation devices, and their performance is poor. For example, one of the existing technologies, Chinese patent application CN118359838A, proposes a MXene aerogel, a preparation method, and a hydrovoltaic power generation device. Specifically, the following steps are taken: preparing a solution A containing a crosslinking agent aldehyde and MXene, and a solution B containing chitosan and glacial acetic acid, mixing the A and B solutions in a certain proportion to prepare a pregel solution, and finally obtaining the MXene aerogel through directional freezing and drying. The output power of the hydrovoltaic power generation device is 0.252 μW / cm 2 The shortcomings of this technical solution are as follows: 1) The preparation process of the hydrovoltaic device requires long freeze-drying time, which is very costly; 2) The contact resistance of the MXene aerogel sheet is large, and the added cross-linking agent and non-conductive substances such as chitosan further reduce the conductivity, limiting its water evaporation power generation performance; 3) The output performance of this hydrovoltaic power generation device is poor, with an output power of only 0.252 μW / cm 2 ; 4) In actual application scenarios (such as electrodes in water evaporation power generation devices), the material is often subjected to various mechanical stresses, and its performance will deteriorate due to structural damage during long-term use. Summary of the Invention

[0005] The present disclosure aims to solve at least one of the technical problems existing in the prior art and provide a method for improving the performance of MXene-based water evaporation power generation devices.

[0006] The present disclosure provides a method for improving the performance of a MXene-based water evaporation power generation device, the method comprising:

[0007] FeCl2·4H2O, deionized water, ascorbic acid and ethylene glycol are mixed and introduced with N2 or Ar to obtain an etching solution;

[0008] Add carbon nanotubes to the etching solution, adjust the solution pH to 4.0 ± 0.1, and perform ultrasonic treatment in an ice bath;

[0009] Adding MAX powder to an etching solution containing carbon nanotubes, performing an etching reaction and standing treatment under N2 protection conditions to obtain a supernatant;

[0010] Centrifugally washing and drying the supernatant to obtain a precipitate;

[0011] The precipitate and the acidified CNT are mixed into a MXene / CNT solution, which is filtered through filter paper and dried to obtain a MXene / CNT / filter paper composite film;

[0012] Conductive parts are connected to the upper and lower ends of the MXene / CNT / filter paper composite film to obtain a water evaporation power generation device.

[0013] Optionally, the solid-to-liquid ratio of the FeCl2·4H2O, the ascorbic acid, the ethylene glycol and the deionized water is 20 g:0.1 g:10 mL:80 mL.

[0014] Optionally, the content ratio of the FeCl2·4H2O to the MAX powder is 20:1.

[0015] Optionally, the MAX powder is Ti3AlC2, Ti2AlC or V2AlC.

[0016] Optionally, the content of the carbon nanotubes is 5%-8% of the content of the MAX powder.

[0017] Optionally, the pH of the solution is adjusted to 4.0±0.1 using NaOH solution, and ultrasonic treatment is performed in an ice bath for 2-4 minutes.

[0018] Optionally, the etching reaction temperature range is 40-60° C., the etching time is 2.5-3.5 hours, and the static treatment time is 25-35 minutes.

[0019] Optionally, the centrifuging, washing, and drying the supernatant to obtain a precipitate comprises:

[0020] The supernatant was centrifuged for the first time at 3000-4000 r / min for 20-30 min, then centrifuged for the second time at 6000-8000 r / min for 20-30 min, and dried at 55-65°C for 10-14 h to obtain a precipitate.

[0021] Optionally, the filter paper has a pore size of 0.2-0.3 μm and is made of PTFE.

[0022] The present disclosure proposes a method for improving the performance of a MXene-based water evaporation power generation device, comprising: mixing FeCl2·4H2O, deionized water, ascorbic acid, and ethylene glycol, and introducing nitrogen or argon to obtain an etching solution; adding carbon nanotubes to the etching solution, and adjusting the pH to 4.0±0.1 by dropwise addition of 0.1 M NaOH solution; adding MAX powder to the etching solution, performing an etching reaction and allowing the solution to stand under nitrogen protection to obtain a supernatant; centrifuging and washing the supernatant, and drying the solution to obtain a precipitate; preparing the precipitate into a solution, filtering it through filter paper, and drying it to obtain a MXene / CNT / filter paper composite film; and connecting conductive portions to the upper and lower ends of the MXene / CNT / filter paper composite film to obtain a water evaporation power generation device. The present disclosure utilizes in-situ hydroxyl radical acidification and etching to simultaneously assemble CNTs, thereby chemically bonding the CNTs to the MXene film, effectively improving the current and voltage of the device. The operation is simple, the device does not contain strong acids, and it is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flowchart of a method for improving the performance of a MXene-based water evaporation power generation device according to a specific embodiment of the present disclosure;

[0024] Figure 2 This is a scanning electron microscope image of MXene in Example 1 of the present disclosure;

[0025] Figure 3 This is a comparison chart of the resistance of MXene and MXene / CNT in Example 1 of the present disclosure;

[0026] Figure 4 This is a comparison test chart of the long-term output voltage of the MXene and MXene / CNT water evaporation power generation devices of Example 1 of the present disclosure;

[0027] Figure 5 This is a comparative test diagram of the long-term output current of the MXene and MXene / CNT water evaporation power generation devices of Example 1 of the present disclosure;

[0028] Figure 6This is a test diagram of the output voltage and current of the MXene water evaporation power generation device with an external load resistor according to Example 1 of the present disclosure;

[0029] Figure 7 This is a test diagram of the output power of the MXene water evaporation power generation device with an external load resistance according to Example 1 of the present disclosure;

[0030] Figure 8 This is a long-term output voltage and current test diagram of the MXene / CNT water evaporation power generation device of Example 2 of the present disclosure;

[0031] Figure 9 This is a long-term output voltage and current test diagram of the MXene / CNT water evaporation power generation device of Example 3 of the present disclosure. DETAILED DESCRIPTION

[0032] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present disclosure and are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present disclosure.

[0033] like Figure 1 As shown, the present disclosure provides a method S100 for improving the performance of a MXene-based water evaporation power generation device, specifically comprising the following steps S110 to S160:

[0034] S110, FeCl2·4H2O, deionized water, ascorbic acid and ethylene glycol are mixed, and N2 or Ar is introduced to obtain an etching solution.

[0035] Specifically, add FeCl₂·4H₂O to a three-necked flask, followed by deionized water, and stir at 250-350 rpm until completely dissolved. Then, add ascorbic acid and ethylene glycol. Purge the solution with nitrogen or argon (N₂) for 10-20 minutes (at a flow rate of 40-60 mL / min) to remove dissolved oxygen.

[0036] In some preferred embodiments, the solid-to-liquid ratio of FeCl2·4H2O, the ascorbic acid, the ethylene glycol and deionized water is 20 g:0.1 g:10 mL:80 mL.

[0037] This embodiment uses Fe 2+ solution and ascorbic acid to form an etching solution, Fe 2+ Inserted into the MXene interlayer, it weakens the interlayer electrostatic repulsion and expands the interlayer distance through ion hydration. In addition, it can also reduce the oxygen-containing groups on the MXene surface (such as -Ti-O- ), destroying the interlayer hydrogen bond network and promoting peeling. In addition, the ascorbic acid disproportionation reaction produces hydrogen peroxide, Fe 2+ The Fenton reaction with hydrogen peroxide produces hydroxyl radicals, which attack Al. The strong oxidizing property of hydroxyl radicals enables it to destroy the chemical bonds between Al atoms and surrounding atoms. After the Al layer is attacked, it undergoes an oxidative dissolution reaction and reacts with hydroxyl radicals to produce Al2O3 and water. As the Al layer is continuously oxidized and dissolved, the structure of the MAX phase is gradually destroyed, exposing the internal atomic layers of Ti and C. As the Al layer is removed (etched), the original MAX phase (for example, Ti3AlC2) gradually transforms into MXene (for example, Ti3C2T x On the other hand, the hydroxyl radicals produced by ascorbic acid will oxidize the CNTs added in the subsequent steps, thereby achieving the purpose of acidifying the CNTs and forming -COOH on the surface of the CNTs. In this dominant process, the pH value is crucial. In an acidic environment of pH = 4, the edge Ti in MXene 4+ It is still positively charged, forming charge complementarity with the acidified CNTs and undergoing electrostatic self-assembly, allowing the CNTs to self-assemble in situ on the MXene surface and form chemical bonds, which helps to improve the conductivity. Compared with the traditional HF etching method, it avoids the use of fluoride and greatly reduces environmental and health risks.

[0038] It should also be noted that based on the Fe 2+ Oxidized to Fe 3+ , and ascorbic acid can convert Fe 3+ Reduction back to Fe 2+ This circulation mechanism ensures that there are always enough active species (·OH) in the etching solution to maintain the continuity of the etching reaction, greatly improving the reaction efficiency and continuous etching ability of the etching solution.

[0039] S120, adding carbon nanotubes to the etching solution, adjusting the pH of the solution to 4.0±0.1, and performing ultrasonic treatment in an ice bath.

[0040] In step S120, the carbon nanotube content is 5%-8% of the MAX powder content. The solution pH can be adjusted to 4.0±0.1 using a 0.1M NaOH solution, and ultrasonic treatment is performed in an ice bath for 2-4 minutes, preferably 3 minutes. The ice bath treatment lowers the temperature of the reaction system, slowing the reaction rate and preventing excessive etching. Furthermore, ultrasonic treatment evenly disperses the carbon nanotubes in the etching solution. The ultrasonic cavitation effect allows the etching reagent to more effectively impact the MAX powder surface, increasing contact between the etching reagent and the MAX powder and exposing reactive sites, thereby accelerating the etching reaction and helping to ensure a more uniform etching reaction across the surface of the MAX powder particles.

[0041] In this embodiment, carbon nanotubes are added to the etching solution and the pH value is adjusted to a specific value to acidify the carbon nanotubes and make their surface hydrophilic. In this way, the hydrophilic surface of the CNTs carries groups that are conducive to reaction with the MAX powder, avoiding local etching or insufficient etching, and also facilitating water evaporation for power generation.

[0042] S130, adding MAX powder to the etching solution, performing etching reaction and standing treatment under N2 protection conditions to obtain a supernatant.

[0043] Specifically, MAX powder was added to the flask at a uniform and slow speed using a medicine spoon, and N2 protection was continuously introduced at 40-60° C. The reaction was carried out for 2.5-3.5 hours, and the mixture was allowed to stand for 25-35 minutes.

[0044] In some preferred embodiments, the MAX powder is Ti3AlC2, Ti2AlC or V2AlC.

[0045] S140, centrifuging, washing, and drying the supernatant to obtain a precipitate.

[0046] Specifically, the supernatant was centrifuged and washed for the first time at 3000-4000 r / min for 20-30 min, and then centrifuged and washed for the second time at 6000-8000 r / min for 20-30 min, and then dried at 55-65° C. for 10-14 h to prevent product oxidation.

[0047] S150, preparing the precipitate into a solution, filtering it with filter paper, and drying it to obtain a MXene / CNT / filter paper composite film.

[0048] Specifically, the obtained precipitate sample was prepared into a solution at a specific mass ratio, filtered through a vacuum apparatus (using filter paper as the filtration membrane), and dried at room temperature to obtain a MXene / CNT / filter paper composite film. In other words, in this embodiment, after filtration, the filter paper was laminated to the bottom of the MXene / CNT layer, forming a three-layer composite film.

[0049] In some preferred embodiments, the pore size of the filter paper is 0.2-0.3 μm, and the filter paper is made of PTFE.

[0050] This embodiment directly forms the film by vacuum filtration without freeze-drying, which has a simple process and low cost. The formed composite film sheets are tightly stacked, which is conducive to the selective passage of ions.

[0051] S160. Connect conductive parts to the upper and lower ends of the MXene / CNT / filter paper composite film to obtain a water evaporation power generation device.

[0052] In this embodiment, MXene, CNTs, and filter paper are combined to form a composite film. Hydroxyl radicals generated during the MXene etching process can in situ acidify the CNTs and induce self-assembly. Numerous micron-scale channels in the filter paper at the bottom of the composite film supply water molecules to the MXene / CNT film above through capillary action. The double electric layer formed in the nanochannels between the carbon nanotubes and MXene sheets selectively passes ions in the water, ultimately creating a potential difference between the top and bottom ends of the composite film.

[0053] In addition, it is worth noting that the Ti 4+ Carboxyl groups generated by oxidation and other surface treatments on CNTs undergo a dehydration condensation reaction under appropriate conditions to form Ti-OC, forming a chemical bond between the two. This chemical bond (e.g., Ti-OC bonding) is a strong interaction. In the MXene / CNT / filter paper composite film, the MXene and CNTs are tightly connected by chemical bonds. This prevents relative displacement or separation of the MXene and CNTs when subjected to external physical stresses (such as bending, stretching, and friction). In practical applications, chemical bonding ensures that the material will not degrade due to structural damage over long-term use. Furthermore, this chemical bonding reduces electron scattering and obstruction at the interface, lowering interfacial resistance and thus improving the overall conductivity of the device. Furthermore, in cases involving ion transport (such as ion migration associated with water evaporation), the optimized interface facilitates more orderly ion movement within the nanochannels constructed by the MXene and CNTs.

[0054] Furthermore, CNTs interspersed between MXene sheets or attached to their surfaces effectively "stitch" or "bridge" adjacent MXene sheets. This significantly reduces contact resistance between MXene sheets caused by stacking, poor edge contact, or the presence of insulating functional groups or impurities. Furthermore, the incorporation of CNTs physically prevents the close stacking (or restacking) of MXene sheets, maintaining a larger interlayer spacing and facilitating the transport of ions and electrons. The CNTs themselves form independent, one-dimensional conductive pathways throughout the composite, forming an interconnected 3D conductive network with the two-dimensional pathways of the MXene. Electrons can hop between the MXene and CNT networks, providing more efficient transport pathways. Favorable interfacial interactions (such as van der Waals forces, π-π interactions, or possibly covalent bonding) help reduce contact resistance between MXene sheets and CNTs and facilitate charge transfer between them.

[0055] In addition, the porosity of the filter paper facilitates the rapid transport of water during water evaporation, while providing a uniformly loaded substrate for MXene / CNT, which can provide physical support for the MXene film and prevent swelling caused by prolonged immersion in water. Secondly, filtration results in a smaller interlamellar spacing in the MXene film, and the double electrical layer between the layers enhances the selectivity of ions. In addition, the structure of the filter paper allows the MXene film to better contact the tab, because the filter paper can spread the MXene film more evenly in the tab contact area, increasing the contact area, which is conducive to the efficient transfer of charge from the composite film to the tab, thereby deriving the current and improving the power generation efficiency.

[0056] The water evaporation power generation device of this embodiment features low cost, a simple process flow, high current and voltage output, and long-term stability. The MXene surface of the resulting composite film is rich in hydrophilic functional groups (such as -O and -OH), which promote water molecule adsorption and evaporation to drive power generation. The tightly packed MXene sheets form nanochannels, enabling selective ion transport and enhancing power generation efficiency. The complementary conductive network formed by the CNTs and the porous structure of the filter paper ensure device stability and environmental adaptability.

[0057] The following is a method for improving the performance of MXene-based water evaporation power generation devices, which will be further described with reference to specific examples:

[0058] Example 1

[0059] S1. Add 20 g of FeCl2·4H2O to a three-necked flask, add 80 mL of deionized water, and stir until completely dissolved at 300 rpm. Add 0.1 g of ascorbic acid and 10 mL of ethylene glycol. Flow nitrogen through the solution for 15 minutes (flow rate 50 mL / min) to eliminate dissolved oxygen to obtain an etching solution.

[0060] S2. Add 60 mg of carbon nanotubes (CNT mass fraction is 5% of the MAX content) to the etching solution, add 0.1 M NaOH solution dropwise to adjust the pH to 4.0 ± 0.1, and ultrasonicate in an ice bath for 3 min.

[0061] S3. Use a medicine spoon to slowly and evenly add 1.0 g of Ti3AlC2 into the flask, continue to introduce N2 for protection, react for 3 h, let it stand for 30 min, and obtain the supernatant.

[0062] S4. The supernatant was placed in a centrifuge tube and washed once with 0.01 M HCl solution (pH approximately 6) at a centrifugal speed of 35,000 r / min for 20 min. The supernatant was then washed twice with deionized water at a centrifugal speed of 7,000 r / min for 20 min to obtain a precipitate. The precipitate was finally dried in a vacuum oven at 60°C for 12 h (to prevent product oxidation).

[0063] S5. The obtained precipitate sample is prepared into a solution with a certain mass fraction, and dried at room temperature using a vacuum filtration device (the filtration membrane is filter paper, and the pore size of the filter paper is 0.22 μm) to obtain a MXene / CNT / filter paper composite film.

[0064] S6. At room temperature, tabs were installed on both ends of the MXene / CNT composite film to obtain a water evaporation power generation device based on the MXene / CNT composite film. The device size was 1×2 cm.

[0065] like Figure 2 As shown, the uniformly distributed CNTs form a 3D conductive network on the MXene sheet, which improves the electron transmission speed.

[0066] It should be noted that this embodiment also provides a comparative example, in which step S2 is removed to obtain a MXene / filter paper composite film.

[0067] like Figure 3 As shown in the figure, the conductivity of the MXene / CNT / filter paper composite film is increased by about 3 times compared with the MXene / filter paper composite film, reaching 7800 S / cm.

[0068] Furthermore, one end of the prepared water evaporation power generation device was placed in a beaker containing 0.3 M NaCl solution, so that the seawater partially submerged the MXene / filter paper composite film. The voltage and current between the tabs were measured using Keithley 2450. The results are as follows: Figure 4 and Figure 5 The output voltage and current density of the device formed by the MXene / CNT / filter paper composite film reached 0.8 V and 50.8 μA·cm, respectively.-2 , which is much higher than the performance of MXene power generation devices without CNT loading (0.54 V and 12.2 μA·cm -2 In addition, the output time is as long as 30,000 s, and the voltage and current do not change significantly during long-term use, demonstrating the excellent stability of the device.

[0069] Figure 6 The external load resistance of the MXene / CNT / filter paper composite thin film power generation device prepared in this embodiment varies from 10 2 Ω~10 8 Ω output voltage and output current test diagram.

[0070] like Figure 6 As shown, the output voltage and output current of the MXene / CNT / filter paper composite thin film power generation device were tested with an external load resistance of 10 2 Ω~10 8 Ω. As the load resistance increases from 10 2 Ω increases to 10 8 Ω, the output voltage increases from nearly 0V to 0.8V; at the same time, the current increases from 48.2 μA·cm -2 Dropped to close to 0.

[0071] Figure 7 The external load resistance of the MXene / CNT / filter paper composite thin film power generation device prepared in this embodiment varies from 10 2 Ω~10 8 Ω output power test chart.

[0072] like Figure 7 As shown, the output power of the MXene / CNT / filter paper composite thin film power generation device was tested with an external load resistance of 10 2 Ω ~10 8 Ω. When the load resistance is 4.3×10 5 When Ω, the maximum output power density can be obtained to be 9.66 μW / cm 2 .

[0073] Example 2

[0074] The preparation method of the water evaporation power generation device of the MXene / filter paper composite film in this example is the same as that of Example 1, except that in step S3, the material selected is Ti2AlC, the etching time is set to 2 h, and one end of the obtained water evaporation power generation device is placed in a beaker containing 0.3 M NaCl solution, so that the seawater partially submerges the MXene / filter paper composite film. The current between the tabs is measured using Keithley2450. The results are as follows: Figure 8 As shown in Figure 2, the output voltage and current density of the device are 0.77 V and 47.2 μA·cm, respectively. -2 , the output time is up to 30000 s.

[0075] Example 3

[0076] The preparation method of the water evaporation power generation device of the MXene / filter paper composite film in this example is the same as that of Example 1, except that in step S3, the material selected is V2AlC, the etching time is set to 3.5 h, and one end of the obtained water evaporation power generation device is placed in a beaker containing 0.3 M NaCl solution, so that the seawater partially submerges the MXene / CNT / filter paper composite film. The current between the tabs is measured using Keithley2450. The results are as follows: Figure 9 As shown, the output voltage and current density of the device are 0.75 V and 46.1 μA·cm, respectively. -2 , the output time is up to 30000 s.

[0077] This disclosure proposes a method for improving the performance of MXene-based water evaporation power generation devices, which has the following beneficial effects compared to the prior art:

[0078] (1) The MXene preparation method proposed in the present invention does not contain highly toxic and dangerous chemicals and is green and environmentally friendly;

[0079] (2) The in-situ hydroxyl radical acidification and etching method for simultaneous CNT assembly proposed in the present invention is not only simple to operate, but also does not contain strong acid and is environmentally friendly;

[0080] (3) The MXene / CNT thin film water evaporation power generation device proposed in the present invention has low cost and simple operation process, does not require long-term freeze-drying, and has a certain degree of flexibility, making it suitable for large-scale production.

[0081] (4) The composite CNTs proposed in the present invention can improve the conductivity of the film on the one hand, and increase the surface potential of the film on the other hand, thereby simultaneously increasing the current and voltage of the device, so that the device has high voltage and current output and long-term stability;

[0082] (5) The chemical bonding between the CNT and MXene of the present invention has good stability, which avoids problems such as structural destruction during long-term use and resulting in performance degradation.

[0083] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for improving the performance of a MXene-based water evaporation power generation device, characterized in that: The method comprises: FeCl2·4H2O, deionized water, ascorbic acid and ethylene glycol are mixed and introduced with N2 or Ar to obtain an etching solution; Add carbon nanotubes to the etching solution, adjust the solution pH to 4.0 ± 0.1, and perform ultrasonic treatment in an ice bath; Adding MAX powder to an etching solution containing carbon nanotubes, performing an etching reaction and standing treatment under N2 protection conditions to obtain a supernatant; Centrifugally washing and drying the supernatant to obtain a precipitate; The precipitate is prepared into a solution, filtered through filter paper, and dried to obtain a MXene / CNT / filter paper composite film; Conductive parts are connected to the upper and lower ends of the MXene / CNT / filter paper composite film to obtain a water evaporation power generation device.

2. The method according to claim 1, characterized in that The solid-to-liquid ratio of the FeCl2·4H2O, the ascorbic acid, the ethylene glycol and the deionized water is 20 g:0.1 g:10 mL:80 mL.

3. The method according to claim 1, characterized in that The content ratio of the FeCl2·4H2O to the MAX powder is 20:

1.

4. The method according to claim 1, wherein The MAX powder is Ti3AlC2, Ti2AlC or V2AlC.

5. The method according to claim 1, wherein The content of the carbon nanotubes is 5%-8% of the content of the MAX powder.

6. The method according to claim 1, characterized in that The pH of the solution was adjusted to 4.0±0.1 using NaOH solution, and ultrasonic treatment was performed in an ice bath for 2-4 min.

7. The method according to claim 1, characterized in that The temperature range of the etching reaction is 40-60° C., the time is 2.5-3.5 hours, and the static treatment time is 25-35 minutes.

8. The method according to claim 1, characterized in that The supernatant is centrifuged, washed, and dried to obtain a precipitate, comprising: The supernatant was centrifuged and washed with HCl solution at 3000-4000 r / min for 20-30 min, and the supernatant was centrifuged and washed at least twice with deionized water at 6000-8000 r / min for 20-30 min each time, and then vacuum dried at 55-65°C for 10-14 h to obtain a precipitate.

9. The method according to claim 1, characterized in that The filter paper has a pore size of 0.2-0.3 μm and is made of PTFE.

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