Preparation method of efficient water evaporation MXene-CuS pyramid array photo-thermal structure

Abstract

The invention provides a preparation method of an efficient water evaporation MXene-CuS pyramid array photo-thermal structure. The preparation method comprises the following steps: preparing MXene; preparing foamy copper CF with a pyramid array structure; the foamy copper CF is converted into a CuS nanowire structure CuS (at) CF; mXene and CuS (at) CF are compounded, and MXene-CuS (at) CF is obtained. According to the preparation method, cutting, in-situ synthesis and impregnation are taken as main methods, and the efficient MXene-CuS-CF solar evaporator for solar-driven water evaporation is prepared. The MXene-CuS-coated CF evaporator disclosed by the invention shows outstanding evaporation performance and output power performance. According to the MXene-CuS-CF bionic interface evaporator, through the multi-scale structure design and the efficient photo-thermal synergistic effect, the evaporation performance and the energy utilization rate are remarkably improved, and an efficient and environment-friendly solution is provided for solving the problem of global fresh water resource shortage. Therefore, the technology is expected to promote the practical application of the technology in fresh water-energy co-production in remote areas and islands in the future, and the sustainable development of seawater desalination and renewable energy utilization is promoted.

Description

Technical Field

[0001] The present invention relates to the field of photothermal evaporation technology, and more particularly to a method for preparing a Romanesco-inspired MXene-CuS pyramid array photothermal structure for efficient water evaporation. Background Art

[0002] Desalination is one of the most effective ways to solve the problem of water shortage. Traditional desalination technologies include multi-stage flash evaporation, reverse osmosis, electrodialysis and membrane distillation. However, they have certain limitations, such as high cost, high energy consumption, increased environmental pollution, impact on the balance of marine ecosystems and limited scope of application. In addition, traditional desalination technology is even more of a waste of money for individual and emergency freshwater acquisition. Therefore, there is an urgent need for a green, simple and portable technology to obtain fresh water. Solar-driven interfacial evaporation technology is an emerging freshwater acquisition technology with simple equipment, scalability and portability. It uses clean and inexhaustible solar energy as the only energy input, converts solar energy into heat energy and positions it at the water-air interface. It uses the principle of photothermal conversion to achieve seawater evaporation at the air-water interface to directly obtain fresh water.

[0003] To date, a variety of photothermal materials with different energy conversion principles have been developed for solar-driven water evaporation. However, challenges remain in evaporation system design, such as poor evaporation performance and low energy efficiency. Therefore, this research aims to develop a new, multifunctional photothermal evaporator, focusing on the development of safe, efficient, and sustainable composite photothermal materials. This research will promote the coordinated development of efficient freshwater evaporation and collection equipment and the coupling of renewable energy sources. Therefore, this invention provides new research ideas for the preparation and development of new solar interfacial evaporators. Summary of the Invention

[0004] To address the aforementioned technical issues, a method for preparing a Romanesco-inspired MXene-CuS pyramid array photothermal structure for high-efficiency water evaporation is provided. This high-efficiency water evaporation MXene-CuS pyramid array photothermal structure significantly improves evaporation performance and energy efficiency through multi-scale structural design and efficient photothermal synergy, providing a highly efficient and environmentally friendly solution to addressing global freshwater resource shortages.

[0005] The technical means adopted in the present invention are as follows:

[0006] A method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure, comprising:

[0007] S1. Preparation of MXene;

[0008] S2. Preparation of copper foam CF with pyramid array structure;

[0009] S3. Converting copper foam CF into CuS nanowire structure CuS@CF

[0010] S4. Compound MXene with CuS@CF to obtain MXene-CuS@CF.

[0011] Furthermore, step S1 specifically includes:

[0012] S11. Add 40% HF and deionized water to a polytetrafluoroethylene beaker;

[0013] S12, weighing an appropriate amount of Ti3AlC2 and slowly adding it to a polytetrafluoroethylene beaker, stirring continuously to react, and centrifuging the slurry after the reaction to obtain an upper liquid and a lower precipitate, until the pH value of the upper liquid is close to neutral, and then ending the centrifugation operation;

[0014] S13, adding dimethyl sulfoxide (DMSO) to react with the lower precipitate, and washing several times after the reaction to remove the residual dimethyl sulfoxide (DMSO);

[0015] S14. After centrifugation, the upper liquid and lower precipitate are dried to obtain a few layers and a thin layer of MXene.

[0016] Furthermore, in step S12, the centrifugal operation is carried out under the following centrifugal conditions: a rotation speed of 15000 r / s and a time of 10 min.

[0017] Furthermore, in step S14, the drying temperature of the drying operation is 40°C.

[0018] Furthermore, step S2 specifically includes:

[0019] S21, a foam copper plate with a size of 20 mm × 20 mm × 10 mm was subjected to low-speed multi-pass wire cutting using a molybdenum electrode with a diameter of 0.1 mm to obtain 3D foam pyramid structures in four different arrays: a planar 4×4 array, a 6×6 array, and an 8×8 array;

[0020] S22. Wash with deionized water and dry in a vacuum oven to obtain a foam copper CF having a pyramid array structure.

[0021] Furthermore, step S3 specifically includes:

[0022] S31, ultrasonically cleaning the copper foams of different arrays with HCl, isopropyl alcohol, and deionized water, respectively;

[0023] S32, dissolve (NH4)2S2O8 and NaOH in deionized water and stir rapidly;

[0024] S33, placing different arrays of copper foam in the above solution to react to generate CuO nanowires CuO@CF, and washing the mixture with deionized water for multiple times;

[0025] S34, dissolving Na2S9H2O in deionized water to obtain a homogeneous Na2S solution;

[0026] S35. Place the CuO@CF generated in step S33 in a homogeneous Na2S solution for reaction, take it out and wash it with deionized water to remove unreacted products, thereby obtaining CuS nanowires CuS@CF.

[0027] Furthermore, step S4 specifically includes:

[0028] S41, adding MXene powder to deionized water, and mixing uniformly with ultrasonic vibration to obtain a MXene solution;

[0029] S42, CuS nanowires CuS@CF with different sizes were immersed in MXene solution multiple times;

[0030] S43. After taking it out, dry it in a vacuum oven to obtain a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure.

[0031] Furthermore, in step S41, the concentration of the MXene powder is 10 ppm.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. The present invention adopts cutting, in-situ synthesis and impregnation as the main methods to prepare MXene-CuS@CF solar evaporator for efficient solar-driven water evaporation.

[0034] 2. The MXene-CuS@CF evaporator of the present invention exhibits outstanding evaporation performance and output power performance. The MXene-CuS@CF bionic interface evaporator significantly improves the evaporation performance and energy utilization through multi-scale structural design and efficient photothermal synergistic effect.

[0035] 3. The technology of the present invention can be applied in the fields of seawater desalination and waste heat reuse. It is also expected to promote the practical application of this technology in the cogeneration of freshwater and energy in remote areas and islands in the future, and promote the sustainable development of seawater desalination and renewable energy utilization.

[0036] Based on the above reasons, the present invention can be widely promoted in fields such as photothermal evaporation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 Schematic diagram comparing the photothermal conversion process of the Roman broccoli-inspired MXene-CuS pyramid array photothermal structure for efficient water evaporation in the present invention.

[0039] Figure 2 Schematic diagram of the preparation process of the high-efficiency water evaporation MXene-CuS pyramid array photothermal structure of the present invention.

[0040] Figure 3 This is a scanning electron microscope image of Ti3AlC2 provided in an embodiment of the present invention.

[0041] Figure 4 This is a scanning electron microscope image of the MXene provided in an embodiment of the present invention.

[0042] Figure 5 This is a scanning electron microscope image of the CF provided by an embodiment of the present invention.

[0043] Figure 6 This is a SEM image of CuS@CF provided by an embodiment of the present invention.

[0044] Figure 7 This is a scanning electron microscope image of MXene-CuS@CF provided in an embodiment of the present invention.

[0045] Figure 8 This is the EDS spectrum of MXene-CuS@CF provided in an embodiment of the present invention.

[0046] Figure 9 EDS spectra and atomic percentages of elements in MXene-CuS@CF provided in an embodiment of the present invention.

[0047] Figure 10 A digital photo of the lightweight MXene-CuS@CF provided by an embodiment of the present invention.

[0048] Figure 11 Dynamic water contact angles of CF, CuS@CF, and MXene-CuS@CF provided in the embodiments of the present invention.

[0049] Figure 12 Fourier transform infrared spectra of CF, CuS@CF, and MXene-CuS@CF provided in the embodiments of the present invention.

[0050] Figure 13 XRD of CF, CuS@CF and MXene-CuS@CF provided in the embodiments of the present invention.

[0051] Figure 14 Cu 2p spectrum of CuS@CF provided in an embodiment of the present invention.

[0052] Figure 15 This is the S2p spectrum of CuS@CF provided in an embodiment of the present invention.

[0053] Figure 16 Ti 2p spectrum of MXene-CuS@CF provided in an embodiment of the present invention.

[0054] Figure 17 Thermogravimetric analysis of MXene-CuS@CF provided in an embodiment of the present invention.

[0055] Figure 18 This is the reflectivity of the MXene-CuS@CF provided in the embodiment of the present invention in a wet state.

[0056] Figure 19 Schematic diagram of light reflection of MXene-CuS@CF provided in an embodiment of the present invention.

[0057] Figure 20 UV-visible-near-infrared spectrum of the wet MXene-CuS@CF provided in an embodiment of the present invention.

[0058] Figure 21 The temperature changes of CF, CuS@CF, and MXene-CuS@CF during the photothermal conversion process provided by the embodiments of the present invention.

[0059] Figure 22 DRS spectrum (diffuse reflectance spectrum) of MXene-CuS@CF provided in an embodiment of the present invention.

[0060] Figure 23 Tauc curve of MXene-CuS@CF provided in an embodiment of the present invention (a curve used to analyze the optical band gap of the material)

[0061] Figure 24 Schematic diagram of the photothermal conversion mechanism of MXene-CuS@CF provided in an embodiment of the present invention.

[0062] Figure 25 A model diagram of the experimental device for solar-driven water evaporation and a schematic diagram of water evaporation in a MXene-CuS@CF evaporator provided in an embodiment of the present invention.

[0063] Figure 26 The embodiment of the present invention provides a 1kW m-2 Mass loss of an 8×8 array pyramidal photothermal structure made of different photothermal materials under illumination conditions.

[0064] Figure 27 The embodiment of the present invention provides a 1kW m -2 Evaporation rate of an 8×8 array pyramidal photothermal structure of different photothermal materials under illumination conditions.

[0065] Figure 28 The embodiment of the present invention provides a 1kWm -2 Mass change curves of different MXene-CuS@CF pyramid array structures under illumination conditions.

[0066] Figure 29 The embodiment of the present invention provides a 1kWm -2 Evaporation rates of different MXene-CuS@CF pyramid array structures under illumination conditions.

[0067] Figure 30 The evaporation rate of the MXene-CuS@CF provided in the present embodiment was compared with that of previously reported work.

[0068] Figure 31 This is a test of the evaporation stability of the MXene-CuS@CF provided in an embodiment of the present invention after ten cycles.

[0069] Figure 32 The mass change of MXene-CuS@CF provided by the embodiment of the present invention under different salt concentrations for 1 hour.

[0070] Figure 33 The evaporation rate of MXene-CuS@CF provided in an embodiment of the present invention at different salt concentrations for 1 hour.

[0071] Figure 34 The mass change of MXene-CuS@CF provided by the embodiment of the present invention after continuous evaporation for 8 h at different salt concentrations.

[0072] Figure 35 The evaporation rate of MXene-CuS@CF provided in the embodiment of the present invention is continuously evaporated for 8 hours under different salt concentrations.

[0073] Figure 36 The changes in the concentrations of the four main ions before and after seawater desalination provided by the embodiment of the present invention.

[0074] Figure 37 The ion retention rate provided by the embodiment of the present invention.

[0075] Figure 38 Schematic diagram of the solar temperature difference power generation process provided by an embodiment of the present invention.

[0076] Figure 39 The temperature difference across the TEG under 0.5, 1, and 1.5 suns provided in the embodiment of the present invention.

[0077] Figure 40 This is a graph of the short-circuit current, open-circuit voltage, and maximum power density of MXene-CuS@CF provided by an embodiment of the present invention under 0-1.5 sun irradiation.

[0078] Figure 41 The embodiment of the present invention provides the stability of the temperature difference between the two ends of the TEG when the sunlight intensity is 0.5, 1 and 1.5 suns.

[0079] Figure 42 The open circuit voltage cycling stability of the TEG provided by the embodiment of the present invention.

[0080] Figure 43 The short-circuit current cycling stability of the TEG provided by the embodiment of the present invention.

[0081] Figure 44 A comparison of the thermoelectric properties of MXene-CuS@CF provided in this embodiment of the present invention with previously reported work. DETAILED DESCRIPTION

[0082] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0083] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0084] like Figure 1 As shown, the present invention provides a method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure inspired by Roman broccoli, comprising:

[0085] S1. Preparation of MXene;

[0086] S2. Preparation of copper foam CF with pyramid array structure;

[0087] S3. Converting copper foam CF into CuS nanowire structure CuS@CF

[0088] S4. Compound MXene with CuS@CF to obtain MXene-CuS@CF.

[0089] When specifically implemented, as a preferred embodiment of the present invention, Figure 2 As shown, step S1 specifically includes:

[0090] S11. Add 40% HF and deionized water to a polytetrafluoroethylene beaker;

[0091] S12, weighing an appropriate amount of Ti3AlC2 and slowly adding it to a polytetrafluoroethylene beaker, stirring continuously to react, and centrifuging the slurry after the reaction to obtain an upper liquid and a lower precipitate, until the pH value of the upper liquid is close to neutral, and then ending the centrifugation operation;

[0092] S13, adding dimethyl sulfoxide (DMSO) to react with the lower precipitate, and washing several times after the reaction to remove the residual dimethyl sulfoxide (DMSO);

[0093] S14: After centrifugation, the upper liquid layer and the lower precipitate layer are dried to obtain a few layers and a thin layer of MXene. The drying temperature of the drying operation is 40°C.

[0094] In this embodiment, the preparation of MXene specifically includes: adding 20mL of 40% hydrofluoric acid (HF) and 15mL of deionized water to a 100mL polytetrafluoroethylene beaker, weighing 2g of Ti3AlC2, and slowly adding it to the polytetrafluoroethylene beaker (to prevent local oxidation to produce TiO2). React at 40°C for 10 hours. After the reaction is completed, the above slurry is centrifuged at 15000rpm for 10 minutes until the pH value of the upper layer of the slurry is close to neutral. Then 25mL of dimethyl sulfoxide (DMSO) is added to the precipitate and stirred at room temperature for 12 hours. After the reaction is completed, the residue is washed with deionized water to remove residual DMSO. After centrifugation, the upper layer of the solution is a single-layer MXene dispersion, and the lower layer of the residue is dried in a vacuum drying oven at 40°C for 12 hours to obtain a small amount of MXene thin layer such as Figure 2 (a).

[0095] In specific implementation, as a preferred embodiment of the present invention, step S2 specifically includes:

[0096] S21, a foam copper plate with a size of 20 mm × 20 mm × 10 mm was subjected to low-speed multi-pass wire cutting using a molybdenum electrode with a diameter of 0.1 mm to obtain 3D foam pyramid structures in four different arrays: a planar 4×4 array, a 6×6 array, and an 8×8 array;

[0097] S22. Wash with deionized water and dry in a vacuum oven to obtain a foam copper CF having a pyramid array structure.

[0098] In this embodiment, the preparation of CF specifically includes: using the Sodick slow wire cutting method to process an array pyramid structure on a foam copper plate (length, width and height of 20mm×20mm×10mm) with a pore size of 100ppi. A molybdenum electrode with a diameter of 0.1mm is used, and low-speed multi-pass cutting is performed during the wire cutting process. The processing parameters are: pulse width 16μs, pulse interval 96μs, short-circuit current 1A, open-circuit voltage 105V, and wire speed 5.2mm. 2 After cutting, four different arrays of 3D foam pyramid structures were obtained: plane, 4×4 array, 6×6 array, and 8×8 array. The 3D foam pyramid structures were then washed with deionized water and dried in a vacuum oven to obtain a foam copper CF with a pyramid array structure.

[0099] When implementing the invention, please refer to the preferred embodiment of the invention. Figure 1 , step S3 specifically includes:

[0100] S31, ultrasonically cleaning the copper foams of different arrays with HCl, isopropyl alcohol, and deionized water, respectively;

[0101] S32, dissolve (NH4)2S2O8 and NaOH in deionized water and stir rapidly;

[0102] S33, placing different arrays of copper foam in the above solution to react to generate CuO nanowires CuO@CF, and washing the mixture with deionized water for multiple times;

[0103] S34, dissolving Na2S9H2O in deionized water to obtain a homogeneous Na2S solution;

[0104] S35. Place the CuO@CF generated in step S33 in a homogeneous Na2S solution for reaction, take it out and wash it with deionized water to remove unreacted products, thereby obtaining CuS nanowires CuS@CF.

[0105] In this embodiment, the preparation of CuS@CF specifically includes: first, the foam copper of different arrays is ultrasonically cleaned with 1MHCl, isopropanol and deionized water for 20 minutes respectively to remove surface impurities and oxides. Then, (NH4)2S2O8 (1.48g, 0.13M) and NaOH (5g, 2.5M) are dissolved in 50mL of deionized water and stirred rapidly. The foam copper of different arrays is placed in the above solution and reacted for 30 minutes to generate CuO nanowires (CuO@CF), and then washed with deionized water multiple times. Na2S·9H2O (0.12g, 50mM) is dissolved in 100mL of deionized water to obtain a Na2S homogeneous solution. Finally, CuO@CF is placed in the Na2S solution and reacted for 2 hours. After being taken out, it is washed with deionized water to remove unreacted products to obtain CuS nanowires (CuS@CF).

[0106] When implementing the invention, please refer to the preferred embodiment of the invention. Figure 1 , step S4 specifically includes:

[0107] S41. Add MXene powder to deionized water and mix uniformly by ultrasonic vibration to obtain a MXene solution; the concentration of the MXene powder is 10 ppm.

[0108] S42, CuS nanowires CuS@CF with different sizes were immersed in MXene solution multiple times;

[0109] S43. After taking it out, dry it in a vacuum oven to obtain a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure.

[0110] In this embodiment, the preparation of MXene-CuS@CF specifically includes: taking 0.1g MXene powder and adding it into 10mL deionized water, mixing it uniformly with ultrasonic vibration, and obtaining MXene solution (10mg mL -1 ), CuS@CF with different sizes were immersed in MXene solution for many times, and then dried in a vacuum oven at 50 °C for 5 h to obtain the final sample MXene-CuS@CF. Figure 2 (b).

[0111] Example 1: Structural Characterization and Analysis of a Romanesco-Inspired MXene-CuS Pyramid Array Solar Steam Generator for Efficient Water Evaporation

[0112] like Figure 3 As shown in the SEM image, it can be seen that the original Ti3AlC2 is a loose block structure. After HF selective etching, as shown in Figure 4As shown in the figure, Ti3AlC2 is transformed into an accordion-shaped lamellar structure. After magnification, it can be seen that the etching degree is good and the lamellar distribution is relatively uniform, indicating that MXene has been successfully prepared. Figure 5 As shown in the figure, the original foam copper skeleton is cleaned simply. It can be seen from the figure that it has a clear three-dimensional network structure and a relatively smooth surface. Figure 6 As shown in the figure, after chemical corrosion, the surface of the copper foam changes from brown to black. From the local enlarged image, it can also be seen that the CuS nanowires are evenly distributed on the CF surface, and the nanowires are mainly composed of CuO in the inner layer and crystalline CuS in the outer layer. Figure 7 As shown in Figure 1, MXene is uniformly deposited around and within the microstructured CuS nanowires and interlocked within the framework. The introduction of CuS and MXene gradually increases the pore density and decreases the pore size of the CF, and increases the roughness of the copper foam surface. This rough surface and porous structure not only increases the composite's absorption of solar energy, but also the hydroxyl-containing polar groups in the introduced MXene promote capillary action, which is beneficial for the generation of water vapor. Finally, as Figure 8 and Figure 9 As shown in Figure 3, the surface distribution and content of Ti, Cu, C, S, O, N, and F elements in MXene-CuS@CF can be further detected by EDS element mapping and atomic percentage analysis.

[0113] like Figure 10 As shown, the lightweight nature of MXene-CuS@CF is demonstrated, which can be placed on flower leaves. Figure 11 Contact angle tests of CF, CuS@CF and MXene-CuS@CF. The contact angle of the original CF is 126°, which is hydrophobic. Figure 12 The Fourier transform infrared (FTIR) spectra shown in the figure show that the CuS@CF and MXene-CuS@CF after chemical etching and sulfurization have a peak at 3561 cm-1 compared with the pure CF infrared spectra. -1 and 3556cm -1 A strong OH characteristic peak appeared around the original CF skeleton surface, which has strong hydrophilic groups CuS and MXene. The contact angle of CuS@CF and MXene-CuS@CF was significantly reduced to 0°. Due to its excellent hydrophilicity, it provides a guarantee for water transmission and is conducive to water evaporation. In addition Figure 12 The FTIR spectra shown further reveal the changes in the functional groups of CF, CuS@CF, and MXene-CuS@CF. CF mainly shows characteristic absorption peaks related to copper, as well as possible organic impurities. -1 The absorption peak at 493 cm is attributed to the CH stretching vibration. -1The absorption peak at 3561cm is related to the vibration of metal-metal bond, which is mainly due to the crystal structure characteristics of copper. CuS-CF mainly shows absorption peaks related to CuS, such as - The absorption peak at 1 may be due to the OH stretching vibration of water molecules adsorbed on the CuS surface. - The absorption peak at 1 may be related to the NH stretching vibration of ammonium persulfate during the composite process. -1 The absorption peak at 679 cm is related to the vibration of the S-Cu bond in CuS. -1 , 441cm -1 and 409cm -1 The absorption peak at 3556 cm-1 may be related to the lattice vibration of CuS. MXene-CuS@CF mainly shows the absorption peaks related to CuS and MXene. With the introduction of MXene, the OH and NH peaks in CuS-CF shift to low angles, and their absorption peaks are located at 3556 cm-1 and 3556 cm-1, respectively. - 1 and 3291cm - 1, indicating the stretching vibration caused by the formation of intermolecular hydrogen bonds in MXene-CuS@CF. - 1. 683cm - 1 and 609cm - These lower wavenumber peaks at 1 may be related to the vibration of Ti-O and Ti-C bonds in the layered structure of MXene and the stretching vibration of S-Cu bonds in CuS, while the peaks at 480 cm - The absorption peak at 1 is related to the low-frequency vibration of (Ti-O-Ti) metal-metal in the layered structure of MXene. In addition, the relative intensity of the OH and NH peaks in MXene-CuS is slightly reduced, and the peak at 480 cm -1 The absorption peak intensity at increases, again indicating that charge localization is suppressed in the MXene composite with CuS. By comparing the infrared spectra of these three materials, we can infer the chemical structure and interactions of the components in the MXene-CuS@CF composite, thereby improving the overall electron mobility and overall conductivity of the MXene-CuS@CF evaporator.

[0114] The phase and crystal structure of CF, CuS-CF and MXene / CuS-CF composites were studied by XRD test. Figure 13As shown in the figure, the diffraction peaks at 34.3°, 36°, and 60.8° are consistent with the (110) and (103) crystal planes of MXene, and the diffraction peaks at 35.9° and 39.5° are consistent with the (208) and (213) crystal planes of the CuS standard card (PDF#06-0464). In addition, except for MXene, each sample has three high diffraction peaks locked at 44.9°, 50.4°, and 72.3°, which are consistent with the (311), (220), and (420) crystal planes of the Cu standard card (PDF#04-0836). Obviously, the presence of CuS and MXene characteristic peaks can be clearly seen in the CuS-CF and MXene / CuS-CF samples, and the overall diffraction peak signal of the MXene / CuS-CF composite material is weakened, indicating that CuS-CF and MXene have been effectively composited and the CuS nanowires are wrapped by MXene.

[0115] XPS was used to characterize the elemental composition, elemental chemical state, and electronic state of CF, CuS@CF, and MXene-CuS@CF nanocomposites. Figure 14 As shown, the XPS full spectrum test of CF, CuS@CF and MXene-CuS@CF. Compared with the total peak spectrum of CF and CuS@CF, the presence of S element in CuS and characteristic elements Ti and F in MXene were detected in the total peak spectrum of MXene-CuS@CF, which is consistent with the characterization results of MXene-CuS@CF and EDS Mapping.

[0116] However, due to the interaction between the addition of MXene and the surface elements of CuS@CF, the intensity of the characteristic element signal peak of CuS@CF is weakened. In order to better understand the electronic coupling between CuS and MXene, such as Figure 15-17 As shown in Figure 2, S2p, Cu 2p and Ti2p were studied by peak separation. Figure 15 As shown in Figure 2, the Cu2p spectrum can be deconvoluted into 6 different characteristic peaks. The peaks at 932.4, 934.8, 943.6 and 945.0 eV correspond to Cu0, Cu 2+ and Cu2p 3 / 2 Satellite peaks in the spectral region. Meanwhile, the peaks at 952.3, 954.6 and 962.6 eV are closely related to Cu 0 、Cu 2+ and Cu2p 1 / 2 The satellite peaks in the spectral phase region correspond to each other. Figure 16 As shown, in the S2p spectrum, the peaks near 162.3eV and 163.9eV belong to the S2p 3 / 2 and S2p 1 / 2The peak at 169.1eV belongs to the satellite peak in the S2p spectral region. Compared with the XPS spectra of Cu 2p and S2p of CuS@CF, the relative peak intensity of the satellite peak of MXene-CuS@CF is significantly enhanced, while the relative intensity of other bonding bonds is significantly weakened, indicating that CuS has a strong interaction with the -O, -F and -OH functional groups on the MXene surface. Figure 17 As shown, the Ti 2p spectrum is divided into five component peaks at 455.7 eV, 462.4 eV, 458.0 eV, 458.7 eV, and 464.8 eV. The binding energies of the Ti-C and Ti-F bonds are 455.7 eV and 462.4 eV, respectively. The peak at 458.0 eV is likely due to low-charge titanium ions (TixOy). The binding energies of 458.7 eV and 464.8 eV correspond to TiO2 and TiOS. These results indicate that the MXene-CuS@CF composite was successfully synthesized, with MXene and CuS bonded together via Ti-S bonds.

[0117] The thermal stability of the product was tested by TG and DTG curves of thermogravimetric analyzer (TGA). Figure 18 As shown, two major weight loss phases can be observed in MXene-CuS@CF during heating, with peaks at 168.2°C and 243.4°C, and weight loss rates of -0.33% / min and -0.05% / min, respectively. These weight losses are related to the thermal decomposition or volatilization of different components in the material. The weight loss at 168.2°C may be related to the evaporation of water adsorbed on the surface of the material or the release of volatiles. The higher weight loss rate in this phase indicates that water and water vapor are weakly bound to the material and are easily released at lower temperatures. The lower weight loss rate at 243.4°C may be related to the decomposition or structural changes of some CuS in the material. Furthermore, at 797.7°C, the residual mass of the material is 98.48%, indicating that the majority of the material remains stable at high temperatures, with only a small amount of components decomposing or volatilizing at high temperatures. Overall, the main components in MXene-CuS@CF exhibit excellent thermal stability at high temperatures.

[0118] like Figure 19 As shown in Figure 2, it is found that the reflectivity of MXene-CuS@CF is low in the entire wavelength range, indicating that it has good light absorption performance (the calculation formula is shown in the Supporting Information). Figure 20The microstructure of MXene-CuS@CF shows that MXene nanosheets and CuS nanowires are evenly distributed on the CF surface, forming a three-dimensional porous structure. This structure promotes multiple reflections and scattering of light, accelerates the transfer of heat from local "hot spots" to the entire material, greatly reduces the transmission of light through internal pores and the reflection of light from the surface into the air, significantly reducing the transmittance of MXene-CuS@CF, thereby improving light absorption efficiency. Figure 21 As shown in Figure 2, MXene-CuS@CF has the highest absorbance in the visible-near infrared spectrum of 200-2500nm, which further verifies its excellent light absorption performance, which is beneficial to water evaporation and light absorption. In order to further investigate the photothermal conversion performance of different photothermal materials, a photothermal conversion test was carried out ( Figure 22 ). The temperature changes of CF, CuS@CF and MXene-CuS@CF during the photothermal conversion process are shown respectively. The main changes are divided into three stages: the first stage is when the light is turned on, the temperature of the photothermal material rises sharply under the light, reaches the highest temperature, the temperature change tends to be stable, and the surface temperature of the photothermal material reaches the maximum value in the second stage; after the light is turned off, the temperature drops sharply to a stable state in the third stage. Figure 23 As shown in the figure, CuS@CF and MXene-CuS@CF have a significant response to light in the wavelength range of 200-800nm. It is worth noting that MXene-CuS@CF shows a higher level of visible light absorption in the range of 200-800nm, thereby greatly improving the utilization efficiency of visible light. The composite of CuS and MXene extends the absorption spectrum of MXene-CuS@CF to the visible light band. Since the band gap width of the material affects its light absorption ability, according to the Kubelka-Munk equation, (αhv) is plotted. 2 -hv relationship diagram, thus obtaining the Tauc curve. The result is as follows Figure 24 As shown in the figure, the band gap of CF is about 2.01eV, the band gap of CuS@CF is about 1.60eV, and the band gap of MXene-CuS@CF is about 1.26eV. MXene-CuS@CF has a narrower band gap than CF and CuS@CF, indicating that the synergistic effect of the defect band position of MXene-CuS@CF has a strong absorption of visible light. Figure 25The photothermal conversion mechanism of the MXene-CuS@CF composite photothermal material is elucidated as shown in Figure 2. The enhanced light absorption capacity of the MXene-CuS@CF composite can be attributed to several factors. When MXene-CuS@CF is irradiated with light, photons reflected multiple times within the pores are synergistically absorbed by the MXene and CuS, converting them into thermal energy. CuS and MXene provide dual active centers for the activation of MXene-CuS@CF, primarily due to rapid charge transfer between the electron-rich Cu and Ti active centers. The MXene and CuS composite exhibit close atomic arrangement at the interface (uniform distribution of Ti, Cu, S, and C elements). The interface structure allows for a smooth transition of the phonon density of states, minimizing phonon scattering at the interface and thus reducing interfacial thermal resistance. When excited by light, the CuS nanowire network extends the optical path through multiple reflections, increasing light absorption. Photogenerated electrons and holes relax to the band edge, where excess energy is converted into thermal energy. Due to the narrow band gap of CuS, this significantly improves the photothermal conversion efficiency of CuS. The high infrared radiation properties of CuS nanowires combined with MXene nanosheets help achieve a dynamic balance between photothermal generation and heat dissipation, thereby improving the material's overall thermal management performance. The conduction band (CB) and valence band (VB) of CuS form a good match with the energy bands of MXene. This match facilitates the transition of electrons from the CuS (VB) to the MXene (CB), while holes simultaneously transition from the MXene (VB) to the CuS (CB), achieving effective separation of electron-hole pairs. This separation improves the collection efficiency of photogenerated charges, thereby enhancing photothermal conversion efficiency. Furthermore, the localized surface plasmon resonance (LSPR) effect of MXene significantly enhances light harvesting. The LSPR effect causes collective oscillations of free electrons on the metal surface, generating high-energy hot electrons. These hot electrons interact with the photogenerated electron-hole pairs of CuS, causing them to rapidly relax through electron-phonon interactions, efficiently converting the photon energy into lattice vibrations (heat energy), further enhancing the material's light absorption properties and avoiding energy losses from radiative recombination. In summary, the MXene-CuS interface design achieves efficient light-to-heat conversion through a triple mechanism: complementary absorption of LSPR and band gap, optimized phonon transport, and optimized light utilization through surface reflection. This provides new insights into the design of high-performance photothermal conversion materials.

[0119] Example 2: Application of the Romanesco-inspired MXene-CuS pyramid array photothermal structure for efficient water evaporation in fresh water acquisition and thermoelectric power generation systems

[0120] The first step is to place the prepared MXene-CuS@CF in different simulated water environments (pure water) at 1kW m 2Irradiate under light for 1 hour. The evaporation performance is tested using a laboratory simulated solar test device system. The device mainly consists of five main parts: a xenon lamp, an electronic balance, a photothermal reaction evaporator, an infrared thermal imager, and a computer. The evaporation rate and evaporation efficiency of MXene-CuS@CF can be obtained based on the curve of the mass change over time tested by the system. 2 The evaporation cycle efficiency of MXene-CuS@CF was tested 10 times under light.

[0121] like Figure 26 As shown in the figure, it is a model diagram of the experimental device for measuring solar-driven water evaporation and a schematic diagram of water evaporation in the MXene-CuS@CF evaporator. Figures 27-28 As shown in Figure 5, the mass loss of pure water, CF, CuS@CF, and MXene-CuS@CF can be observed over time. The evaporation rates are calculated to be 0.64, 2.58, 2.94, and 3.25 kg m, respectively. -2 h -1 The MXene-CuS@CF pyramid solar thermal structure exhibits the highest water evaporation rate, which is five times higher than that of pure water. To further investigate the effect of structural parameters on solar evaporation performance, MXene-CuS@CF solar thermal structures with different pyramid arrays were fabricated: platform, 4×4 array, 6×6 array, and 8×8 array. Figures 29-30 The water mass change and evaporation rate of different array structures under 1 sun irradiation are shown to be 2.19, 2.57, 2.72, and 3.25 kg m, respectively. -2 h -1 Obviously, the increase in the pyramid array of the photothermal structure gives the pyramid array a larger evaporation surface area, which helps to evaporate more water molecules. The 8×8 array MXene-CuS@CF photothermal structure shows the best evaporation performance, and its evaporation rate is 1.5 times that of the 2D platform MXene-CuS@CF photothermal structure. Figure 31 As shown in the figure, the evaporation rate of the 8×8 array MXene-CuS@CF is significantly superior to that of previous 2D and 3D evaporators. In addition, the evaporation rate of the 3D array evaporator is superior to that of the 2D planar evaporator. Finally, we conducted an evaporation cycle stability test. Figure 32 As shown in Figure 3, the evaporation rate of MXene-CuS@CF remained basically stable during repeated evaporation experiments, demonstrating the evaporation stability and excellent recycling ability of the pyramid-shaped MXene-CuS@CF evaporator.

[0122] The second step is to conduct salt tolerance test on salt water with different concentrations by using xenon lamp to simulate sunlight. Simulated seawater, 5wt%, 10wt% and 20wt% NaCl solution are used as the test seawater with different concentrations. -2 Under illumination (light intensity 100mW cm -2 ) Test the photothermal evaporation performance of MXene-CuS@CF in salt solutions with different concentrations.

[0123] In order to verify the evaporation performance of the material in a salt environment, we investigated the photothermal evaporation performance of MXene-CuS@CF in a salt solution. Figures 33-34 As shown in Figure 2, with the increase of salt ion concentration, the mass change of MXene-CuS@CF decreases during evaporation. The evaporation rates of 5% NaCl, 10% NaCl and 20% NaCl are calculated to be 2.83, 2.54, 2.58 and 2.32 kg m-3, respectively, for simulated seawater. -2 h -1 This phenomenon is attributed to the fact that as salt concentration increases, the ion concentration in the solution rises, and the interaction between water molecules and ions strengthens, leading to an increase in the evaporation enthalpy of water and a decrease in the evaporation rate with increasing salt concentration. In low-salt environments, water molecules are relatively free, resulting in a higher evaporation rate. In high-salt environments, the bonds between water molecules and ions become stronger, causing the evaporation rate to decrease. However, the regular porous structure of the MXene-CuS@CF pyramid array provides a stable channel for water transport and evaporation. Driven by light and heat, water molecules continuously evaporate into water vapor through the pores, causing the salt concentration in the upper half of the evaporator to be higher than that in the lower half, thus forming a salt concentration gradient. According to the principle of osmosis, this salt concentration difference drives water from the low-salt concentration area to diffuse toward the high-salt concentration area, thereby diluting the solution in the high-salt area and inhibiting salt precipitation. Furthermore, the micropores within the pyramid array provide strong capillary transport, allowing water from the low-salt concentration at the bottom to continuously move upward, ensuring the continuity of the water evaporation process while suppressing salt ion retention. This dynamic equilibrium process enables the evaporator to maintain stable operation even in high-salt environments. However, the evaporation rate of the evaporator in 10% brine is greater than that in 5% brine, which may be related to the dynamic migration change of salt during the evaporation process, thereby making the evaporation rate of 10% brine higher. Figure 35 As shown in the figure, the evaporator was tested for 8 hours of continuous evaporation in brine with different concentrations under 1 sun. Obviously, with the increase of salinity concentration, the mass change gradually slowed down. In 20% NaCl brine, the overall evaporation rate decreased due to the enhanced effect of hydrated ions, increased evaporation enthalpy, salting out and obstructed capillary transport. In order to test the durability of MXene-CuS@CF, as shown in the figure, the mass change gradually slowed down with the increase of salinity concentration. In 20% NaCl brine, the overall evaporation rate decreased due to the enhanced effect of hydrated ions, increased evaporation enthalpy, salting out and obstructed capillary transport. Figure 36As shown in Figure 2, 50 evaporation experiments were conducted in simulated seawater, and MXene-CuS@CF showed good evaporation stability. Figures 37-38 As shown in the figure, the four main ions Na in seawater before and after desalination of MXene-CuS@CF were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). + Mg 2+ , K + and Ca 2+ The concentration of desalinated water decreased significantly by 2-3 orders of magnitude compared to the original seawater, meeting the freshwater standards set by the World Health Organization (WHO). The calculated retention rates of all four ions exceeded 99%. These results demonstrate the significant potential of the developed MXene-CuS@CF evaporator for solar-driven desalination.

[0124] The third step is to use a xenon lamp to simulate sunlight and test the thermoelectric performance of the evaporation system under different light intensities through an electrochemical workstation. -2 Under illumination (light intensity 100mW cm -2 ) The short-circuit current, open-circuit voltage and temperature difference across the TEG were tested, and a cyclic stability test was performed under different solar irradiances to evaluate the thermo-electric performance of the system.

[0125] like Figure 39 As shown, it consists of a xenon lamp light source, a circulating water pump, a TE module, a four-channel thermocouple, an electrochemical workstation and a MXene-CuS@CF evaporator. MXene-CuS@CF is placed on the hot end of the TE module with a small air gap to ensure that the energy received by the TE module is residual radiant heat. The thermoelectric device is placed on a water-cooled head, which serves as the cold end of the thermoelectric device and maintains the temperature at 18°C, and is exposed to an environment (temperature of 20°C and humidity of 4%). When the light source is activated, the photothermal response of MXene-CuS@CF starts rapidly, and the absorbed light energy is quickly converted into thermal energy. This conversion causes the temperature of the material to rise, thereby generating high temperature on one side of the heat source of the material, causing a significant temperature difference to quickly form between the heat source and the cold source. As shown Figure 40 As shown in the figure, the temperature difference at both ends of the TEG under different light intensities was tested by four-channel thermocouples. The results show that as the intensity of solar radiation increases, the temperature difference at both ends of the TEG gradually increases. This further drives the charge carriers (electrons and holes) in the thermoelectric material to move and diffuse from the high temperature area to the low temperature area, thereby generating an electric potential difference inside the material and forming an electric current. This current can be collected by an external circuit and used for work or storage. Figure 41 As shown in the figure, the steady-state current-voltage (Ic-Voc) curve is drawn based on the above results. It is calculated that the maximum power density at steady-state conditions of 0, 0.5, 1 and 1.5 sun intensities is 0.001W m-2 , 0.36W m -2 ,1.52W m -2 and 3.19W m -2 As the light intensity increases, the photothermal response of the MXene-CuS@CF end becomes stronger, which enhances the Seebeck effect of TEG and increases the thermoelectric power of MXene-CuS@CF. Cyclic stability performance tests of temperature difference and power generation were carried out under different solar illumination. Figures 42-44 As shown in the figure, the temperature difference and output power generated in each intermittent light on and off cycle remain basically constant, verifying the stability of the MXene-CuS@CF thermoelectric power generation system. Compared with the previously reported work, the evaporator prepared by the present invention is more outstanding than similar evaporators for solar-driven water evaporation and cogeneration ( Figure 44 ). In summary, the MXene-CuS@CF material integrated photothermal evaporation and thermoelectric power generation system provides a promising and feasible solution to solve the shortage of fresh water resources and promote green electricity production.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure, characterized in that: include: S1. Preparation of MXene; S2. Preparation of copper foam CF with pyramid array structure; S3, converting copper foam CF into CuS nanowire structure CuS@CF; S4. Compound MXene with CuS@CF to obtain MXene-CuS@CF.

2. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 1, characterized in that: Step S1 specifically includes: S11. Add 40% HF and deionized water to a polytetrafluoroethylene beaker; S12, weighing an appropriate amount of Ti3AlC2 and slowly adding it to a polytetrafluoroethylene beaker, stirring continuously to react, and centrifuging the slurry after the reaction to obtain an upper liquid and a lower precipitate, until the pH value of the upper liquid is close to neutral, and then ending the centrifugation operation; S13, adding dimethyl sulfoxide to react with the lower precipitate, and washing multiple times to remove residual dimethyl sulfoxide after the reaction is completed; S14. After centrifugation, the upper liquid and lower precipitate are dried to obtain a few layers and a thin layer of MXene.

3. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 2, characterized in that: In step S12, the centrifugal operation is carried out under the following centrifugal conditions: a rotation speed of 15000 r / s and a time of 10 min.

4. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 2, characterized in that: In step S14, the drying temperature of the drying operation is 40°C.

5. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 1, characterized in that: Step S2 specifically includes: S21, a foam copper plate with a size of 20 mm × 20 mm × 10 mm was subjected to low-speed multi-pass wire cutting using a molybdenum electrode with a diameter of 0.1 mm to obtain 3D foam pyramid structures in four different arrays: a planar 4×4 array, a 6×6 array, and an 8×8 array; S22. Wash with deionized water and dry in a vacuum oven to obtain a foam copper CF having a pyramid array structure.

6. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 1, characterized in that: Step S3 specifically includes: S31, ultrasonically cleaning the copper foams of different arrays with HCl, isopropyl alcohol, and deionized water, respectively; S32, dissolve (NH4)2S2O8 and NaOH in deionized water and stir rapidly; S33, placing different arrays of copper foam in the above solution to react to generate CuO nanowires CuO@CF, and washing the mixture with deionized water for multiple times; S34, dissolving Na2S9H2O in deionized water to obtain a homogeneous Na2S solution; S35. Place the CuO@CF generated in step S33 in a homogeneous Na2S solution for reaction, take it out and wash it with deionized water to remove unreacted products, thereby obtaining CuS nanowires CuS@CF.

7. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 1, characterized in that: Step S4 specifically includes: S41, adding MXene powder to deionized water, and mixing uniformly with ultrasonic vibration to obtain a MXene solution; S42, CuS nanowires CuS@CF with different sizes were immersed in MXene solution multiple times; S43. After taking it out, dry it in a vacuum oven to obtain a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure.

8. The method for preparing a high-efficiency water evaporation MXene-CuS pyramid array photothermal structure according to claim 7, characterized in that: In step S41, the concentration of the MXene powder is 10 ppm.

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