A molybdenum disulfide-based hydrogel evaporator with adjustable pore structure and preparation method and application

Abstract

The application discloses a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure and a preparation method and application thereof. The method comprises the following steps: swelling polyvinyl alcohol in deionized water, then dissolving after adding MoS2 nanoparticles, the mass ratio of polyvinyl alcohol and MoS2 nanoparticles is 72:(0.9-3.6), and a mixed solution is obtained; glutaraldehyde and hydrochloric acid are added to the mixed solution under stirring, the ratio of glutaraldehyde and MoS2 nanoparticles in S1 is (80-120) muL:(0.09-0.36) g, a mixed system is obtained, then the mixed system is placed at room temperature in a sealed environment, and a crosslinking system is obtained; the crosslinking system is frozen and dissolved, then the excess glutaraldehyde is removed, and the molybdenum disulfide-based hydrogel evaporator with adjustable pore structure is obtained. The molybdenum disulfide-based hydrogel evaporator overcomes the problems of low light utilization, low photo-thermal conversion efficiency, poor water transmission capacity, salt accumulation and low evaporation rate in the current seawater desalination process.

Description

Technical Field

[0001] This invention belongs to the field of photothermal evaporator preparation and interfacial water evaporation, specifically relating to a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure, its preparation method, and its application. Background Technology

[0002] Although water covers 70% of the Earth's surface, freshwater resources on land account for only 6%, and only 0.4% are directly usable. In recent years, due to rapid population growth and industrial development, the discharge of large amounts of domestic and industrial wastewater has severely damaged groundwater resources. Currently, the population with access to safe drinking water is relatively small. The severe scarcity and pollution of freshwater resources have become urgent problems to be solved. Solar energy, as an environmentally friendly, green, and low-energy-consumption renewable energy source, has received widespread attention in the field of interfacial water evaporation. Since its initial proposal in 2014, solar interfacial water evaporation technology has been rapidly and widely applied due to its advantages such as good light utilization, photothermal conversion efficiency, and energy management. However, its evaporation rate is still limited by some drawbacks, such as low light absorption and photothermal conversion performance, poor salt tolerance, poor water transport capacity, and heat loss.

[0003] A key component in the design of interfacial solar evaporators is their photothermal materials. The design and utilization of photothermal materials are prerequisites for the effective use of interfacial solar evaporators. Currently common photothermal materials include carbon-based materials, plasma nanoparticles, and semiconductor materials. Semiconductors are considered one of the most promising photothermal conversion materials due to their stable solar-to-steam conversion efficiency, good chemical stability, and abundant natural resources.

[0004] Currently, metal sulfides are a type of narrow-bandgap semiconductor material with broad spectral response and good photothermal conversion efficiency among semiconductor-based photothermal materials. Molybdenum disulfide (MoS2) is widely used in solar interfacial evaporation due to its narrow bandgap structure (0.59 eV) and wide light absorption range (from near-ultraviolet to near-infrared), enabling excellent light absorption and photothermal conversion. However, a suitable carrier with good salt resistance and excellent water transport capabilities is currently lacking for the application of molybdenum disulfide in solar photothermal interfacial water evaporation. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, this invention discloses a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure, its preparation method, and its application. The preparation process is simple, low-cost, and the raw materials are readily available. The rich network and porous structure reduce the enthalpy of water evaporation, resulting in high and stable photothermal evaporation efficiency. It also has the advantages of strong light absorption capacity, low raw material cost, ease of mass production, and strong mechanical and chemical stability.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a molybdenum disulfide-based hydrogel evaporator with an adjustable pore structure includes the following steps:

[0008] S1, polyvinyl alcohol is swollen in deionized water, and then MoS2 nanoparticles are added and dissolved. The mass ratio of polyvinyl alcohol to MoS2 nanoparticles is 72:(0.9~3.6) to obtain a mixture.

[0009] S2, glutaraldehyde and hydrochloric acid are added to the mixture under stirring. The ratio of glutaraldehyde to MoS2 nanoparticles in S1 is (80-120) μL: (0.09-0.36) g to obtain a mixed system. The mixed system is then allowed to stand at room temperature in a sealed environment to obtain a crosslinked system.

[0010] S3, the cross-linked system is frozen and dissolved, and then excess glutaraldehyde is removed to obtain a molybdenum disulfide-based hydrogel evaporator with an adjustable pore structure.

[0011] Preferably, in step S1, 7.2 g of polyvinyl alcohol is swollen in 64.8 mL of deionized water for 12–16 h, and then MoS2 nanoparticles are added.

[0012] Preferably, the MoS2 nanoparticles described in S1 are obtained by the following process:

[0013] Mix 1g of MoS2 with 1mL of deionized water in a ball mill jar, and mill for 1-2 hours to obtain a uniform MoS2 suspension. Then dry the MoS2 suspension to obtain MoS2 nanoparticles.

[0014] Preferably, S1 dissolves MoS2 nanoparticles at 85–95°C, and then the mixture is cooled to room temperature before adding glutaraldehyde and hydrochloric acid.

[0015] Preferably, the stirring rate in S2 is 15-25 rpm, and then it is added dropwise to the mixture at rates of 8-10 μL / min and 10-12 μL / min respectively to obtain a mixed system.

[0016] Preferably, in step S2, the mixed system is sealed in a mold with a height of 0.5 to 2 cm and left to stand at room temperature for 22 to 26 hours to obtain a crosslinked system.

[0017] Preferably, in step S3, the crosslinking system is frozen at -22 to -18°C for 7 to 9 hours, then dissolved at 23 to 25°C for 2.5 to 3.5 hours. The above freezing and dissolving process is repeated 6 to 8 times, and then excess glutaraldehyde is removed.

[0018] Furthermore, S3 removes excess glutaraldehyde by soaking in deionized water for 22–26 hours.

[0019] A molybdenum disulfide-based hydrogel evaporator with an adjustable pore structure, obtained by the preparation method of the molybdenum disulfide-based hydrogel evaporator with an adjustable pore structure as described in any one of the above claims.

[0020] Application of molybdenum disulfide-based hydrogel evaporators with adjustable pore structures in solar photothermal interface water evaporation.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention discloses a method for preparing a MoS2-based hydrogel evaporator with an adjustable pore structure. Polyvinyl alcohol (PVA) possesses excellent water swelling capacity and superior hydrophilicity. Its hydrophilic functional groups (-OH) enhance the hydration capacity of the hydrogel, increasing the proportion of water in its network and thus reducing the enthalpy of water vaporization, thereby further accelerating the seawater desalination rate. PVA and glutaraldehyde undergo a crosslinking reaction: two adjacent hydroxyl groups in the PVA chain condense with the aldehyde group of GA to form a stable six-membered ring structure, connecting two different PVA chains into a ring, ultimately forming chain-like PVA molecules, which become a network structure. Excessive MoS2 addition will clog the pores of the PVA hydrogel, affecting water transport; conversely, insufficient MoS2 addition is detrimental to the light absorption of the composite hydrogel. Water, as a polar molecule, is attracted to each other through hydrogen bonds due to the charge difference between O and H atoms. Under normal conditions, water exists in solid (ice), liquid, and gaseous (vapor) states, each with a different hydrogen bond network. Water evaporation involves the breaking of multiple hydrogen bonds to produce isolated gaseous water molecules. Upon condensation, the dynamic hydrogen bond network can be reorganized. The ratio of PVA to GA significantly affects the strength and deformability of the hydrogel. Generally, more crosslinking agent allows each PVA molecule to crosslink with it, forming a denser and more rigid network structure. Insufficient GA weakens the chemical crosslinking, preventing the formation of a stable network structure. This method, utilizing MoS2 with excellent photothermal properties combined with porous PVA hydrogel as a photothermal evaporator for interfacial seawater desalination, offers significant advantages: First, the rational design of this evaporator not only promotes good light absorption efficiency but also achieves efficient light-to-heat conversion, improving the utilization rate of sunlight. Second, the temperature at the interfacial evaporation point is higher than the temperature in the seawater, and this temperature gradient further promotes the upward transport of water. Furthermore, the rapid water evaporation at the interfacial evaporation point drives the cooling effect at the interface, further promoting the upward transport of water. Third, the temperature on the side of the seawater evaporator is slightly lower than the ambient temperature, which allows it to absorb more heat from the environment, thus accelerating the evaporation rate of the seawater. These advantages overcome the problems of poor light utilization, low photothermal conversion efficiency, poor water transport capacity, low evaporation rate due to salt accumulation, and energy loss in the current seawater desalination process.

[0023] Furthermore, a mold with a height of 0.5 to 2 cm can form a suitable hydrogel thickness, which is conducive to the upward transport of water and can avoid the decrease in transport rate caused by excessively long water transport channels and the heat loss caused by excessively thin evaporators.

[0024] The internal gaps, water transport microchannels, and three-dimensional cross-linked polymer network structure of the MoS2-based hydrogel evaporator of this invention ensure rapid water replenishment during seawater evaporation and prevent salt accumulation. It exhibits an excellent interfacial seawater evaporation rate, achieving highly efficient light absorption and heat transfer, excellent salt resistance, low heat and mass transfer, and minimal heat loss, making it widely applicable in solar interfacial evaporation. Its superior performance and polymer network structure design make it a promising seawater desalination evaporator.

[0025] When the MoS2-based hydrogel evaporator of the present invention is used in solar photothermal interface water evaporation, compared with the pure PVA hydrogel evaporator, the seawater evaporation rate of the MoS2 composite hydrogel evaporator with good photothermal performance is significantly improved, and its seawater evaporation rate is increased by about 8 times. Attached Figure Description

[0026] Figure 1 The images show the XRD patterns of the pure PVA hydrogel, MoS2, and the MoS2-based hydrogel obtained in this invention.

[0027] Figure 2 The storage dynamic mechanical analysis spectra of the PVA hydrogel prepared in this invention and the MoS2-based hydrogel of Example 2 are shown.

[0028] Figure 3 The interfacial evaporation rate spectra of different MoS2-based hydrogel evaporators prepared in this invention under single-light irradiation are shown.

[0029] Figure 4 This is the SEM image of the MoS2-based hydrogel obtained in Example 2 of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These descriptions are intended to explain the invention and not to limit it.

[0031] The present invention discloses a method for preparing a MoS2-based hydrogel evaporator with adjustable pore structure, comprising the following steps:

[0032] Step 1: Add 7.2g of PVA to 64.8mL of water and soak for 12-16 hours to allow it to swell;

[0033] Step 2: Mix 10g MoS2 and 10mL deionized water in a ball mill jar, mill for 1-2 hours to obtain a uniform MoS2 suspension, and dry to obtain MoS2 nanoparticles. Add 0.09-0.36g of ball-milled MoS2 to the PVA aqueous solution prepared in Step 1 above, and dissolve in a water bath at 85-95℃ for 4-6 hours to obtain a mixture.

[0034] Step 3: Cool the mixture to room temperature. Add 80-120 μL of GA and 120 μL of 20% hydrochloric acid dropwise in sequence under slow stirring (15-25 rpm, as rapid mechanical stirring will introduce air and generate bubbles in the solution). The speed of addition should be 8-10 μL / min and 10-12 μL / min respectively, to ensure sufficient contact and reaction between the two and the solution, forming a more homogeneous mixture. If the dropping speed is too fast, the solution and crosslinking agent will react locally, forming local gels and affecting the final state. After stirring evenly, place the mixture into a mold with a height of 0.5-2 cm and seal it. Let it stand at room temperature for 22-26 hours to allow the PVA chains to undergo chemical crosslinking, thus obtaining the crosslinked system.

[0035] Step 4: Freeze the crosslinking system at -22 to -18°C for 7 to 9 hours, then dissolve it at 23 to 25°C for 2.5 to 3.5 hours. Repeat this freezing and dissolving cycle 6 to 8 times. This will form microcrystalline regions inside the system as physical crosslinking points, thus obtaining a three-dimensional network structure of MoS2-based hydrogel. Then, soak it in deionized water for 22 to 26 hours to remove excess crosslinking agent GA. The thickness should be 0.5 to 2 cm. If the thickness is too high, it will affect the upward transport of water. Conversely, if the thickness of the evaporator is too thin, it will cause heat loss. Both will affect the evaporation rate. A MoS2-based hydrogel evaporator with an adjustable pore structure is obtained. It has a rich network porous structure, and MoS2 is uniformly attached to the surface of the hydrogel. It can be used in solar photothermal interface water evaporation.

[0036] Example 1

[0037] Weigh 10g of MoS2, dissolve it in 10mL of deionized water, mix it in a ball mill jar, and mill for 1 hour to obtain a uniform MoS2 suspension. Dry it at 60℃ to obtain MoS2.

[0038] 7.2 g of PVA was added to 64.8 mL of water and soaked for 14 h to allow it to swell. Then, 0.09 g of MoS2 nanoparticles were added to the PVA aqueous solution and dissolved in a 90°C water bath for 4 h. The resulting mixture was then cooled to room temperature, and 100 μL of GA and 120 μL of 20% hydrochloric acid were added dropwise to the solution at 10 μL / min and 12 μL / min, respectively, while stirring at 15 rpm, to form the final mixture.

[0039] The mixture is uniformly injected into and sealed into a mold, and reacted at room temperature for 24 hours to allow the PVA chains to undergo chemical cross-linking.

[0040] Then, the freeze-thaw cycle was repeated 8 times by freezing at -20°C for 8 hours and thawing at 25°C for 3 hours.

[0041] Finally, after soaking in deionized water for 24 hours to remove excess crosslinking agent GA, a chemically crosslinked MoS2-based composite hydrogel was obtained.

[0042] Example 2

[0043] Weigh 10g of MoS2, dissolve it in 10mL of deionized water, mix it in a ball mill jar, and mill for 1 hour to obtain a uniform MoS2 suspension. Dry it at 60℃ to obtain MoS2.

[0044] 7.2 g of PVA was added to 64.8 mL of water and soaked for 12 h to allow it to swell. Then, 0.18 g of MoS2 nanoparticles were added to the PVA aqueous solution and dissolved in a 90°C water bath for 5 h. The resulting mixture was then cooled to room temperature, and 100 μL of GA and 120 μL of 20% hydrochloric acid were added dropwise to the solution at 9 μL / min and 11 μL / min, respectively, while stirring at 20 rpm, to form the final mixture.

[0045] The mixture is uniformly injected into and sealed into a mold, and reacted at room temperature for 24 hours to allow the PVA chains to undergo chemical cross-linking.

[0046] Then, the freeze-thaw cycle was repeated 8 times by freezing at -20°C for 8 hours and thawing at 25°C for 3 hours.

[0047] Finally, after soaking in deionized water for 24 hours to remove excess crosslinking agent GA, a chemically crosslinked MoS2-based composite hydrogel was obtained.

[0048] Example 3

[0049] Weigh 10g of MoS2, dissolve it in 10mL of deionized water, mix it in a ball mill jar, and mill for 1 hour to obtain a uniform MoS2 suspension. Dry it at 60℃ to obtain MoS2.

[0050] 7.2 g of PVA was added to 64.8 mL of water and soaked for 16 h to allow it to swell. Subsequently, 0.36 g of MoS2 nanoparticles were added to the above PVA aqueous solution and dissolved in a water bath at 90 °C for 6 h. The resulting mixture was then cooled to room temperature, and 100 μL of GA and 120 μL of 20% hydrochloric acid were added dropwise to the above solution at a stirring rate of 25 rpm and a stirring rate of 8 μL / min and 10 μL / min, respectively, to form the final mixture.

[0051] The mixture is uniformly injected into and sealed into a mold, and reacted at room temperature for 24 hours to allow the PVA chains to undergo chemical cross-linking.

[0052] Then, the freeze-thaw cycle was repeated 8 times by freezing at -20°C for 8 hours and thawing at 25°C for 3 hours.

[0053] Finally, after soaking in deionized water for 24 hours to remove excess crosslinking agent GA, a chemically crosslinked MoS2-based composite hydrogel was obtained.

[0054] The sample prepared in Example 2 was subjected to X-ray diffraction to obtain the following results: Figure 1 The XRD diffraction pattern shown. Figure 1 MoS2 exhibited clear diffraction peaks at 14.38°, 39.54°, 49.79°, 58.33°, and 70.14°, corresponding to the (002), (103), (105), (110), and (108) crystal planes of MoS2 (JCPDS No. 37-1492). Furthermore, the XRD spectrum of the MoS2-based composite hydrogel showed that the presence of MoS2 significantly reduced the intensity of the unique peaks in PVA, indicating a decrease in the crystallinity of the PVA hydrogel (obtained by removing MoS2 in Example 2) due to weakened hydrogen bonding. These properties further confirm the successful preparation of the MoS2-based composite hydrogel.

[0055] The hydrogel prepared in Example 2 was subjected to dynamic mechanical analysis. For example... Figure 2 As shown, for both PVA hydrogels and MoS2-based composite hydrogels, the storage modulus (G') is higher than the loss modulus (G”), indicating the formation of the bulk structure and the successful preparation of the hydrogel. For the MoS2-based composite hydrogel, G' and G” are lower than those of PVA, suggesting that PVA is affected by MoS2, and the addition of MoS2 restricts the relative sliding of the PVA polymer chains.

[0056] Take the hydrogel samples prepared in Examples 1-3 and cut them into squares with a side length of 5cm for interfacial water evaporation experiments. Figure 3As shown, all MoS2-based composite hydrogel materials outperform PVA hydrogels. The MoS2-based composite hydrogel prepared in Example 2 had an evaporation rate of 3.948 kg / m³ at 1 sun. -2 h -1 Higher than 0.627 kg m of PVA -2 h -1 The solar-driven water evaporation efficiency can reach 95.2%. Examples 1 (3.428 kg m⁻² h⁻¹) and 3 (3.704 kg m⁻² h⁻¹) are shown. -2 h -1 The evaporation rates of the samples were all lower than those of Example 2, demonstrating that the appropriate introduction of MoS2 into the porous samples can further improve the interfacial water evaporation performance.

[0057] Preparation of simulated seawater: The simulated seawater consisted of NaCl 26.5 g / L, MgSO4 3.30 g / L, MgCl2 2.40 g / L, CaCl2 1.30 g / L, KCl 0.70 g / L, NaHCO3 0.20 g / L, and NaBr 0.08 g / L. The pH of the simulated seawater was 7.0.

[0058] Activity testing procedure: Examples 1-3 and pure PVA hydrogel were cut into 5cm side-length interfacial evaporators. Simulated seawater was placed in a beaker, and the hydrogel was placed on the surface of the simulated seawater. The outer walls were wrapped with foam to prevent heat loss. The bottom of the hydrogel was in contact with the water to facilitate water transfer, while the top was used to receive solar energy, with solar intensity ranging from 0.5 to 1.5 sun. During the experiment, ambient temperature and humidity were measured and monitored using a multi-functional thermo-hygrometer. The surface temperature of the hydrogel's light-absorbing layer and the water temperature were measured using an infrared thermal imager. Changes in water mass were recorded using a high-precision analytical balance. Figure 3 The curve shown. From Figure 3 It can be seen that the samples of Examples 1 to 3 have significantly improved interfacial water evaporation efficiency compared with pure PVA hydrogel. Meanwhile, the hydrogel evaporator prepared in Example 2 has the strongest water evaporation efficiency, and the water collected after evaporation is fresh water.

[0059] like Figure 4 As shown, the hydrogel evaporator prepared in Example 2 has a rich network porous structure, with MoS2 uniformly attached to the surface of the hydrogel, and the pore size of the hydrogel is 1-2 μm.

Claims

1. A method for preparing a molybdenum disulfide-based hydrogel evaporator with an adjustable pore structure, characterized in that, Includes the following steps: S1, polyvinyl alcohol is swollen in deionized water, and then MoS2 nanoparticles are added and dissolved. The mass ratio of polyvinyl alcohol to MoS2 nanoparticles is 72:(0.9~3.6) to obtain a mixture. S2, glutaraldehyde and hydrochloric acid were added dropwise to the mixture at rates of 8-10 μL / min and 10-12 μL / min, respectively, while stirring at a rate of 15-25 rpm. The ratio of glutaraldehyde to MoS2 nanoparticles in S1 was (80-120) µL : (0.09-0.36) g. The mixture was then sealed in a mold with a height of 0.5-2 cm and allowed to stand at room temperature for 22-26 h to obtain a crosslinked system. S3. The crosslinked system is frozen at -22~-18℃ for 7~9 h, and then dissolved at 23~25℃ for 2.5~3.5 h. The above freezing and dissolution process is repeated 6~8 times. After that, excess glutaraldehyde is removed to obtain a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure.

2. The method for preparing a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure according to claim 1, characterized in that, S1: 7.2g of polyvinyl alcohol was dissolved in 64.8 mL of deionized water for 12-16 hours, and then MoS2 nanoparticles were added.

3. The method for preparing a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure according to claim 1, characterized in that, The MoS2 nanoparticles described in S1 are obtained through the following process: Mix 1 g of MoS2 with 1 mL of deionized water in a ball mill jar, mill for 1-2 hours to obtain a uniform MoS2 suspension, and then dry the MoS2 suspension to obtain MoS2 nanoparticles.

4. The method for preparing a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure according to claim 1, characterized in that, S1 dissolves MoS2 nanoparticles at 85~95℃, and then the mixture is cooled to room temperature before adding glutaraldehyde and hydrochloric acid.

5. The method for preparing a molybdenum disulfide-based hydrogel evaporator with adjustable pore structure according to claim 1, characterized in that, S3 removes excess glutaraldehyde by soaking in deionized water for 22-26 hours.

6. A molybdenum disulfide-based hydrogel evaporator with adjustable pore structure obtained by the preparation method of the molybdenum disulfide-based hydrogel evaporator with adjustable pore structure according to any one of claims 1 to 5.

7. The application of the molybdenum disulfide-based hydrogel evaporator with adjustable pore structure as described in claim 6 in solar photothermal interface water evaporation.

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