A preparation method of titanium nitride composite hydrogel for solar water purification

Abstract

The application discloses a preparation method of a titanium nitride composite hydrogel for solar water purification, and belongs to the fields of solar water evaporation, nanomaterial synthesis and polymer composite materials. The prepared semiconductor composite hydrogel has good photo-thermal conversion performance and solar evaporation stability. In the application, TiN nanodots are prepared by a liquid-phase crushing process, a PEI layer is coated on the surfaces of the TiN nanodots by a surface modification method, and the obtained nanodot material has excellent photo-thermal conversion capability and hydrophilicity. A PAM / cellulose porous hydrogel matrix with a three-dimensional porous structure is prepared by using a cyclic freezing and thawing method, and the TiN@PEI nanodots are dispersed in the three-dimensional skeleton structure to obtain a three-dimensional solar water evaporation material with excellent performance. The water evaporation rate of the TiN@PEI / PAM / Cel composite hydrogel material in the application reaches 3.86 kg m ‑2 h ‑1 under the irradiation of 1 solar light intensity.

Description

Technical Field

[0001] This invention belongs to the fields of semiconductor nanocomposite hydrogel synthesis and solar water vaporization technology, and in particular, a method for preparing titanium nitride composite hydrogels for solar water purification. Background Technology

[0002] With global population growth, environmental pollution, and climate change, many countries are suffering from a severe shortage of natural freshwater resources. Seawater desalination is one of the ideal solutions to this pressing problem, as the ocean is the Earth's primary water source. Over the past decade, solar-driven interfacial water evaporation, which utilizes solar energy to generate heat, has emerged as a promising and sustainable process for obtaining freshwater from seawater or wastewater. Furthermore, this fundamental process can be extended to power generation, steam sterilization, fuel production, and more.

[0003] To improve the performance of solar water vaporization, it is essential to increase solar energy absorption, reduce heat loss, prevent salt blockage, and increase water production. Exploring efficient and cost-effective photothermal materials is a primary concern in achieving this goal. To date, a large number of photothermal materials have been developed, including metal nanoparticles, carbon-based materials, and narrow bandgap semiconductors. Among these materials, metal materials are limited by their spectral absorption range, while carbon-based materials, despite their good stability and three-dimensional structure, are difficult to apply on a large scale due to their high cost and difficult fabrication. Nanoplasma materials possess high light absorption rates; however, these noble metal nanoparticles typically absorb one or a few specific narrow wavelengths, which significantly limits the efficiency of solar thermal conversion. In contrast, semiconductor materials, with their tunable bandgap, broad solar spectral absorption range, lower cost, and greater durability, have extremely high research value. Furthermore, semiconductor materials can also possess micro / nano structures through reasonable molding processes and fabrication methods. In the field of solar-driven interfacial evaporation, research on semiconductor materials mainly focuses on materials such as MXenes, cobalt and nickel oxides. Previous reports on semiconductor photothermal material conversion mostly involved the direct addition of commercial materials and simple in-situ synthesis. Some considerable progress has been made by integrating them into two-dimensional (2D) or three-dimensional (3D) evaporators.

[0004] Current interfacial vaporization designs involve a floating solar absorber to absorb solar radiation. This interfacial vaporization system confines heat at the water-air interface, thus suppressing heat loss to the bulk water. Furthermore, integrating all the required optical, thermal, and wetting properties into the material system is challenging; often, the incoherence and incompatibility of multilayer materials and interfaces can lead to optical / thermal losses, instability, and synthetic complexity. Therefore, careful structural design of water evaporators is crucial. Currently reported artificial evaporation structures, bilayer evaporators, and 3D structures have achieved photothermal energy conversion efficiencies exceeding 85%. However, due to the high enthalpy of vaporization of water, the evaporation rate under a single solar irradiation remains relatively low. With a better understanding of water science and the activation of water molecules, the enthalpy of vaporization of large volumes of water can be reduced by modulating the hydrogen bonds formed between water molecules. By introducing various functional groups into solar evaporators, the enthalpy of vaporization of water can be reduced, decreasing the energy required for water evaporation. This is a promising strategy that can significantly improve the water evaporation rate.

[0005] Hydrogels are a unique class of highly porous materials, possessing a three-dimensional cross-linked network, high specific surface area, and excellent water transport and vapor escape properties within the interconnected pores. Their abundant hydroxyl groups endow them with exceptionally high hydrophilicity and the ability to form intermediate water, thereby reducing enthalpy of evaporation and increasing evaporation efficiency. Ultrafine TiN, on the other hand, is a semiconductor material exhibiting a plasmonic effect, possessing an excellent high light absorption range and strong photothermal conversion capabilities. However, the composite of these two materials is limited by the small size of the nanoparticles and their inability to interact with the polymer chains; therefore, the synthesis of semiconductor nanoparticle composite hydrogels has been relatively rare in previous studies.

[0006] This invention presents a three-dimensional porous PAM / cellulose crosslinked hydrogel prepared using a cyclic freeze-thaw method. Its water-transporting capacity is highly matched to the evaporation rate of the surface semiconductor composite material, while also exhibiting good durability. The process is simple and has a short production cycle. TiN nanoparticles are transformed into nanodots via a liquid-phase fragmentation method, increasing TiN dispersibility and active surface utilization, thus enhancing its photothermal capabilities. The cellulose hydroxyl groups in the hydrogel network can crosslink and polymerize with the PEI coating on the TiN nanodot surface, forming multiple and stable hydrogen bonds with the TiN@PEI layer, thereby enhancing the stability of the photothermal composite particles within the hydrogel network. Summary of the Invention

[0007] To overcome the aforementioned problems in the prior art, the present invention provides a method for preparing titanium nitride composite hydrogels for solar water purification.

[0008] The specific technical solution is as follows: A method for preparing titanium nitride composite hydrogels for solar water purification. Specifically, the following steps are included: Step 1: Synthesize TiN nanodots using a liquid-phase disruption method; Step 2: By adjusting the pH and the concentration and dispersion of the particles, a PEI layer is coated onto the surface of the TiN nanodots obtained in Step 1; Step 3: The composite TiN@PEI nanodots obtained in Step 2 are embedded into a three-dimensional porous PAM / cellulose hydrogel network by solution blending to obtain a titanium nitride nanodot composite hydrogel.

[0009] Preferably, step 1 specifically includes the following steps: (1) Add 0.5~1g TiN to 20 mL N-methylpyrrolidone, sonicate in an ice bath for 2 hours, and then sonicate for 24 hours to obtain a black solution; (2) Centrifuge the solution described in step (1) at 5000~10000 rpm for 5 min, wash it repeatedly with ethanol and deionized water, and collect it; (3) Take the material obtained in step (2) and mix it with PVP and add it to 50 ml of ethanol solution. Reflux at a certain temperature for 8 to 12 hours, centrifuge at 5000 to 10000 rpm for 10 min, and wash with deionized water to obtain TiN nanodots.

[0010] Preferably, the ultrasonic stirring in step (1) is a cell disruptor, and the reflux temperature in step (3) is 60°C.

[0011] Preferably, step 2 specifically includes the following steps: (1) Prepare an aqueous solution of polyethyleneimine with pH=5; (2) The aqueous solution described in step (1) is characterized in that the pH of the 0.5~1 wt% PEI solution is adjusted to 5 with concentrated nitric acid; (3) Take 0.5 g of TiN nanodots and disperse them in the PEI aqueous solution described in step (2). Stir and reflux at a certain temperature for 4 hours. After rinsing with deionized water, dry under vacuum at room temperature. (4) The powder obtained in step (3) is sintered at low temperature for 2 hours under nitrogen atmosphere to obtain TiN@PEI nanodot material.

[0012] Preferably, the reflux temperature in step (3) is 100°C, the sintering temperature in step (4) is 120°C, and the heating rate is 5°C / min.

[0013] Preferably, step 3 specifically includes the following steps: (1) Add 0.98g of acrylamide monomer and 1.5% N'N dimethylformamide to 20ml of deionized water and sonicate for 15 min to obtain a clear and transparent AM aqueous solution; (2) Add a quantitative amount of cellulose and 1 wt% ammonium persulfate to the solution in step (1) according to the mass ratio of AM, and stir ultrasonically for 15 min to obtain a mixed solution; (3) Take TiN@PEI nanodot material and add it to the mixture in step (2), and stir ultrasonically for 15 min; (4) Pour the mixture obtained by ultrasonic stirring in step (3) into a mold, freeze it with liquid nitrogen, and then heat it to melt it. Repeat the freeze-thaw process 10 times to obtain a black composite hydrogel.

[0014] Preferably, the melting temperature in step (4) is maintained at 30°C.

[0015] Compared with the prior art, the present invention has the following advantages: (1) This invention provides a method for preparing titanium nitride nanoparticle composite hydrogel for solar water purification. TiN nanoparticles are prepared by liquid-phase fragmentation as a highly efficient photothermal semiconductor nanomaterial. Polyethyleneimine is coated on the outside of TiN nanoparticles to obtain TiN@PEI composite nanoparticles. The surface is coated with a PEI layer to improve hydrophilicity. The water transport matrix is ​​composed of PAM / cellulose porous hydrogel material with a three-dimensional porous structure prepared by cyclic freeze-thaw method. The TiN@PEI composite nanoparticle photothermal material is embedded into a three-dimensional porous PAM / Cel hydrogel network by solution blending. The PAM / Cel network has hydroxyl groups arranged in a high density on the internal 3D network, which has strong hydrophilicity and can form a three-dimensional random channel for rapid water transport from bottom to top. The PEI layer can crosslink and polymerize with Cel to make TiN nanoparticles uniformly distributed in the 3D porous framework without affecting the water transport capacity of the hydrogel matrix. The prepared titanium nitride nanoparticle composite hydrogel has good photothermal conversion performance and solar evaporation stability. Attached Figure Description

[0016] Figure 1 Images of the TiN@PEI / PAM / Cel composite hydrogels prepared in Examples 1 and 2 of this invention; Figure 2 Fourier transform infrared image of the TiN@PEI / PAM / Cel composite hydrogel prepared in Example 1 of this invention; Figure 3 This is a scanning electron microscope image of the TiN@PEI / PAM / Cel composite hydrogel prepared in Example 1 of this invention; Figure 4 The graph shows the water absorption properties of the TiN@PEI / PAM / Cel composite hydrogels prepared in Examples 1 and 2 of this invention. Figure 5The graphs show the water evaporation curves of the TiN@PEI / PAM / Cel composite hydrogel under one solar intensity in Examples 1 and 2 of this invention. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] Combination Figures 1 to 5 The specific implementation is as follows: Example

[0019] A method for preparing a titanium nitride composite hydrogel for solar water purification includes the following steps: 0.5 g TiN was added to 20 mL of N-methylpyrrolidone (NMP). Cells were lysed and sonicated for 2 hours under ice bath conditions. The sonication was maintained at a constant ice bath temperature for 1 hour each time, for a total of 24 hours, to obtain a black solution. The solution was centrifuged at 10,000 rpm for 5 min and washed repeatedly with ethanol and deionized water before collection. 100 mg TiN was mixed with 1 g PVP and added to 50 mL of ethanol solution. The mixture was refluxed at 60 °C for 10 hours, then centrifuged at 10,000 rpm for 10 min and washed with deionized water to obtain TiN nanodots.

[0020] Prepare a 0.5 wt% PEI aqueous solution and adjust the pH of the solution to 5 with concentrated nitric acid; transfer the solution to a flask, add TiN nanodots, stir and reflux at 100℃ for 4 hours, rinse with deionized water, and vacuum dry at room temperature; then transfer the powder to a tube furnace and sinter at 120℃ for 2 hours at 5℃ / min under a nitrogen atmosphere to obtain TiN@PEI nanodot material.

[0021] 0.98 g of AM monomer and 1.5% N'N dimethylformamide were added to 20 ml of deionized water and ultrasonically stirred for 15 min to obtain a clear and transparent AM aqueous solution. Then, 0.14 g of cellulose and 1 wt% ammonium persulfate were added to the AM solution and ultrasonically stirred for 15 min to obtain a mixed solution. 50 mg of TiN@PEI nanodot material was added to the mixed solution and ultrasonically stirred for another 15 min. The above TiN@PEI / AM / cellulose mixture was poured into a mold, frozen with liquid nitrogen, and then heated to 30 °C to thaw. The freeze-thaw process was repeated 10 times to obtain a black TiN@PEI / PAM / Cel composite hydrogel.

[0022] The physical image of the TiN@PEI / PAM / Cel composite hydrogel obtained by the above method is shown below. Figure 1 As shown, TiN nanoparticles were uniformly dispersed into the hydrogel matrix through the above steps, and a hydrogel photothermal evaporation component was fabricated by molding using a custom mold. The Fourier transform infrared spectrum of the obtained TiN@PEI / PAM / Cel composite hydrogel is shown below. Figure 5 As shown in the figure, the characteristic peaks of hydroxyl and amino groups can be seen, indicating that the hydrogel cross-linking structure is intact. Figure 3 The image shows a scanning electron microscope (SEM) image of the obtained TiN@PEI / PAM / Cel composite hydrogel. During the freeze-thaw process, a uniform three-dimensional porous network was formed. The pores with a size of 1-10 μm were generated when intermediate and free water were removed from the hydrogel matrix, while the pores with a size of 50 μm or larger were generated when bound water was forcibly extracted from the polymer network. This three-dimensional network structure with such a pore size can provide stable longitudinal water transport through capillary action and combined with surface hydrophilicity. Example

[0023] A method for preparing a titanium nitride composite hydrogel for solar water purification includes the following steps: 1 g TiN was added to 20 mL of N-methylpyrrolidone (NMP). Cells were lysed and sonicated for 2 hours under ice bath conditions. The sonication was continued at a constant ice bath temperature for 1 hour each time, for a total of 24 hours, to obtain a black solution. The solution was centrifuged at 10,000 rpm for 5 min and washed repeatedly with ethanol and deionized water before collection. 100 mg TiN was mixed with 1 g PVP and added to 50 mL of ethanol solution. The mixture was refluxed at 60 °C for 10 hours, then centrifuged at 10,000 rpm for 10 min and washed with deionized water to obtain TiN nanodots.

[0024] Prepare a 1 wt% PEI aqueous solution and adjust the pH of the solution to 5 with concentrated nitric acid; transfer the solution to a flask, add TiN nanodots, stir and reflux at 100℃ for 4 hours, rinse with deionized water, and vacuum dry at room temperature; then transfer the powder to a tube furnace and sinter at 120℃ for 2 hours at 5℃ / min under a nitrogen atmosphere to obtain TiN@PEI nanodot material.

[0025] 0.98 g of AM monomer and 1.5% N'N dimethylformamide were added to 20 ml of deionized water and ultrasonically stirred for 15 min to obtain a clear and transparent AM aqueous solution. Then, 0.20 g of cellulose and 1 wt% ammonium persulfate were added to the AM solution and ultrasonically stirred for 15 min to obtain a mixed solution. 50 mg of TiN@PEI nanodot material was added to the mixed solution and ultrasonically stirred for another 15 min. The above TiN@PEI / AM / cellulose mixture was poured into a mold, frozen with liquid nitrogen, and then heated to 30 °C to thaw. The freeze-thaw process was repeated 10 times to obtain a black TiN@PEI / PAM / Cel composite hydrogel.

[0026] The water absorption properties of the TiN@PEI / PAM / Cel composite hydrogel and the MoS2@PDA / PAM composite hydrogel obtained by the above method are shown in the figure. Figure 4 As shown, the saturated water content can reach 4.98 g / kg. -1 The water content is 82%, which proves that the prepared material has excellent hydrophilicity and can provide sufficient water for surface evaporation. Figure 5 To test the water evaporation rate of the TiN@PEI / PAM / Cel composite hydrogel material of this invention, it reached 3.86 kg·m under 1 solar intensity irradiation. -2 ·h -1 .

[0027] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a titanium nitride composite hydrogel for solar water purification, characterized in that: Specifically, the following steps are included: Step 1: Synthesize TiN nanodots using a liquid-phase fragmentation method; Step 2: By adjusting the pH and the concentration and dispersion of the particles, a PEI layer is coated onto the surface of the TiN nanodots obtained in Step 1; Step 3: The composite TiN@PEI nanodots obtained in Step 2 are embedded into a three-dimensional porous PAM / cellulose hydrogel network by solution blending to obtain a titanium nitride nanodot composite hydrogel.

2. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 1, characterized in that: Step 1 specifically includes the following steps: (1) Add 0.5~1g TiN to 20 mL N-methylpyrrolidone, sonicate in an ice bath for 2 hours, and then sonicate for 24 hours to obtain a black solution; (2) Centrifuge the solution described in step (1) at 5000~10000 rpm for 5 min, wash it repeatedly with ethanol and deionized water, and collect it; (3) Take the material obtained in step (2) and mix it with PVP and add it to 50 ml of ethanol solution. Reflux at a certain temperature for 8 to 12 hours, centrifuge at 5000 to 10000 rpm for 10 min, and wash with deionized water to obtain TiN nanodots.

3. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 2, characterized in that, The ultrasonic stirring in step (1) is a cell disruptor, and the reflux temperature in step (3) is 60°C.

4. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 1, characterized in that: Step 2 specifically includes the following steps: (1) Prepare an aqueous solution of polyethyleneimine with pH=5; (2) The aqueous solution described in step (1) is characterized in that the pH of the 0.5~1 wt% PEI solution is adjusted to 5 with concentrated nitric acid; (3) Take 0.5 g of TiN nanodots and disperse them in the PEI aqueous solution described in step (2). Stir and reflux at a certain temperature for 4 hours. After rinsing with deionized water, dry under vacuum at room temperature. (4) The powder obtained in step (3) is sintered at low temperature for 2 hours under nitrogen atmosphere to obtain TiN@PEI nanodot material.

5. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 4, characterized in that, The reflow temperature in step (3) is 100℃, the sintering temperature in step (4) is 120℃, and the heating rate is 5℃ / min.

6. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 1, characterized in that, Step 3 specifically includes the following steps: (1) Add 0.98g of acrylamide monomer and 1.5% N'N dimethylformamide to 20ml of deionized water and sonicate for 15min to obtain a clear and transparent AM aqueous solution; (2) Add a quantitative amount of cellulose and 1 wt% ammonium persulfate to the solution in step (1) according to the mass ratio of AM, and stir ultrasonically for 15 min to obtain a mixed solution; (3) Take TiN@PEI nanodot material and add it to the mixed solution in step (2), and stir ultrasonically for 15 min; (4) Pour the mixture obtained by ultrasonic stirring in step (3) into a mold, freeze it with liquid nitrogen, and then heat it to melt it. Repeat the freeze-thaw process 10 times to obtain a black composite hydrogel.

7. The method for preparing a titanium nitride composite hydrogel for solar water purification according to claim 6, characterized in that, The melting temperature in step (4) is maintained at 30°C.

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