Preparation method and application of tellurium nanomaterial

Abstract

The application provides a preparation method of tellurium nanomaterial, comprising: taking a tellurium crystal as a cathode, an inert electrode as an anode, and placing the cathode and the anode in an electrolytic cell containing an electrolyte, applying a working voltage of-2 V to-8 V to the cathode to perform an electrochemical stripping reaction, and obtaining a mixed solution containing tellurium nanomaterial in the electrolytic cell; wherein the electrolyte is an acetonitrile solution containing an electrolytic ionic liquid; performing solid-liquid separation on the mixed solution, and sequentially performing washing and drying on the obtained solid, and the obtained solid material is the tellurium nanomaterial. The preparation method realizes batch and high-yield preparation of Te nanomaterial, and the surface of the tellurium nanomaterial is modified with an electrolysis product of the electrolytic ionic liquid, and the tellurium nanomaterial has various different morphologies, and is particularly suitable for being used as a photothermal material capable of efficiently absorbing solar energy. The application also provides a Te-based composite foam material and a preparation method and application thereof.

Description

Technical Field

[0001] The present application relates to the technical field of nanomaterial preparation, and in particular to a preparation method and application of tellurium nanomaterial. Background Art

[0002] Tellurium (Te) is a p-type semiconductor with a narrow band gap. g ) is only 0.35eV, and has an anisotropic crystal structure composed of spiral chains. It is believed to have great application potential in the fields of solar thermal materials, catalysis, thermoelectricity, piezoelectricity, nonlinear photoresponse, etc., and because of its special chain structure, it can be shaped into nanoscale materials of different dimensions.

[0003] Currently, the main methods for preparing Te nanomaterials include hydrothermal methods and liquid phase exfoliation methods. The products obtained by the hydrothermal method are often accompanied by high-molecular-weight surfactants that cannot be removed, which reduces their quality and photothermal efficiency. While the surface of Te nanomaterials produced by the liquid phase exfoliation method is free of impurities and has high photothermal properties, their yield is low and cannot meet practical application requirements. Therefore, it is necessary to provide a scalable and high-yield method for preparing Te nanomaterials with good photothermal effects, and to enrich their application forms, in particular, to provide a new product that can be used for efficient seawater desalination. Summary of the Invention

[0004] In view of this, the present application provides a method for preparing Te nanomaterials through electrochemical stripping reactions. This method realizes the batch and high-yield preparation of Te nanomaterials by selecting a specific electrolyte containing an electrolytic ionic liquid. The surface of the tellurium nanomaterial is modified with the electrolysis product of the electrolytic ionic liquid and has a variety of different morphologies, which is particularly suitable for use as a photothermal material that can efficiently absorb solar energy.

[0005] Specifically, in a first aspect, the present application provides a method for preparing a tellurium nanomaterial, comprising the following steps:

[0006] A tellurium crystal is used as a cathode and an inert electrode is used as an anode. The cathode and anode are placed in an electrolytic cell filled with an electrolyte, and an operating voltage of -2V to -8V is applied to the cathode to perform an electrochemical stripping reaction, thereby obtaining a mixed solution containing tellurium nanomaterials in the electrolytic cell; wherein the electrolyte is an acetonitrile solution containing an electrolytic ionic liquid;

[0007] The mixed solution is filtered, and the obtained solid matter is washed and dried in sequence, and the obtained solid matter is the tellurium nanomaterial.

[0008] The present application adopts an acetonitrile solution containing an electrolytic ionic liquid as the electrolyte for electrochemical stripping of tellurium crystals, and based on an appropriate stripping voltage (i.e., electrolysis voltage), can achieve electrochemical stripping of tellurium crystals at an appropriate rate, and the resulting tellurium nanomaterial is small in size and has a variety of morphologies (including nanowires, flocculent structures and nanoparticles), which is beneficial to improving its absorption of solar energy light; in addition, the electrolytic ionic liquid undergoes electrolysis of anions and / or cations under the electrolysis voltage, and the electrolytic species of anions / cations can be intercalated into the tellurium crystals to achieve their stripping, and can also modify the surface of the resulting tellurium nanomaterial, thereby improving its stability, improving surface wettability, regulating the electronic structure of the semiconductor, etc., which is more conducive to its practical application.

[0009] In the embodiment of the present application, the electrolytic ionic liquid may include one or more of 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium (methylsulfonyl trifluoro)imide, N-butylpyridine bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpyrrole trifluoromethanesulfonate, etc. Taking 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide as an example, its 1-aminopropyl-3-methylimidazolium cation can be electrolyzed to 1-aminopropyl-3-methylimidazolium free radical, and the electrolysis product of its bis(trifluoromethanesulfonyl)imide anion can include CF3SO2N - CF3SO2 - SO2N - CF3 - etc., tellurium nanomaterials can be modified by at least one of these electrolysis products, such as CF3SO2N - Can form CF3SO2NH-Te with the surface of tellurium nanomaterials.

[0010] In the embodiment of the present application, the concentration of the electrolytic ionic liquid in the electrolyte is 0.05 to 1 mol / L. Specifically, for example, it is 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, or 0.9 mol / L. Controlling the molar concentration of the electrolytic ionic liquid can adjust the stripping efficiency. When the molar concentration of the electrolytic ionic liquid is within the above range, slower stripping of the tellurium nanomaterial can be achieved, resulting in smaller products, which are more conducive to subsequent photothermal applications.

[0011] In the present application, the operating voltage of the electrochemical stripping is in the range of -2V to -8V, specifically -7V, -6V, -5V, -4V, -3V, etc. The electrochemical stripping rate can be regulated by controlling the voltage of the electrochemical stripping. When the voltage is higher, the tellurium stripping speed is generally faster, and the electrolysis time is generally shorter. Among them, the extent of the electrochemical stripping can be monitored by observing the color of the electrolyte. In the embodiment of the present application, the time of the electrochemical stripping reaction can be 5 minutes to 12 hours, for example, 10 minutes, 20 minutes, 0.5h (i.e., 30 minutes), 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 11h or 12h, etc.

[0012] In the present application, the inert electrode can be a graphite electrode or a platinum electrode, preferably a platinum electrode, and specifically can be a platinum wire, a platinum sheet or a platinum rod.

[0013] In this application, after electrochemical stripping, the resulting mixed solution in the electrolytic cell may include tellurium nanomaterials, acetonitrile, and an electrolytic ionic liquid. After solid-liquid separation of the mixed solution, the resulting solids may be washed sequentially with acetonitrile, ethanol, and deionized water. The solid-liquid separation method may include filtration (e.g., vacuum filtration) or centrifugation.

[0014] In the embodiment of the present application, the tellurium nanomaterial includes a variety of different morphologies, and the various different morphologies include nanowires, flocculent structures and nanoparticles, that is, the tellurium nanomaterial includes tellurium nanowires, tellurium nanoparticles, and flocculent tellurium nanomaterials. Among them, tellurium nanowires are one-dimensional materials, tellurium nanoparticles can be three-dimensional or even zero-dimensional materials (when the nanoparticles are small enough, such as quantum dot level), and flocculent tellurium nanomaterials are two-dimensional materials. Among them, the diameter of the tellurium nanowire can be no more than 15nm, for example, 5-15nm, 5-8nm; the length of the tellurium nanowire does not exceed 1.5μm. The diameter of the tellurium nanoparticles can be no more than 100nm, in some embodiments it can be 2-10nm, and in other embodiments it can be 20-100nm. The maximum lateral dimension of the flocculent tellurium nanomaterial does not exceed 100nm.

[0015] As described above, in the embodiment of the present application, the surface of the obtained tellurium nanomaterial is modified with the electrolysis product of the electrolytic ionic liquid. The electrolysis product of the electrolytic ionic liquid can be covalently modified on the surface of the tellurium nanomaterial to improve its stability.

[0016] The methods for preparing tellurium nanomaterials provided in the examples of this application are simple and easy to operate, and can be readily scaled up for production. The products are high in yield, small in size, and well dispersed. The resulting tellurium nanomaterials are rich in chemical groups on their surfaces and can be directly used in related applications.

[0017] In a second aspect, the present application provides a method for preparing a Te-based composite foam material, comprising the following steps:

[0018] (1) mixing tellurium nanomaterials with polyvinyl alcohol (PVA), a crosslinking agent, a foam stabilizer, an acid catalyst, and water at -5 to 10° C. to obtain a precursor solution;

[0019] (2) The precursor solution is stirred at an ultra-high speed at a speed greater than or equal to 10,000 rpm, and is placed at 20-50° C. for cross-linking to obtain a cross-linked composite foam material crude product; the composite foam material crude product is then dialyzed in water to obtain a Te-based composite foam material.

[0020] In the above step (1) of the present application, the tellurium nanomaterial used can be commercially available, or obtained by the preparation method described in the first aspect of the present application, or can be prepared by liquid phase exfoliation, hydrothermal method or other feasible methods. In particular, the tellurium nanomaterial prepared by the preparation method described in the first aspect of the present application has a better absorption effect on sunlight and better stability, and its photothermal effect is more lasting and efficient, and is more suitable for preparing the Te-based composite foam material.

[0021] In step (1), the cross-linking agent in the precursor solution can be selected from one or more of dialdehydes (such as glyoxal, glutaraldehyde), paraformaldehyde, urea-formaldehyde resin, melamine-formaldehyde resin, boride (such as boric acid, sodium borate, zinc borate), maleic anhydride, etc., with glutaraldehyde being preferred. The acid catalyst can be one or more of hydrochloric acid, sulfuric acid, acetic acid, etc., with hydrochloric acid being preferred due to its better catalytic effect. The foam stabilizer can include one or more of alkyl glycosides, cationic surfactants, anionic surfactants, and nonionic surfactants, with the nonionic surfactant segmented polyether F-127 (Pluronic F-127) having a better effect.

[0022] Optionally, in step (2), the mass ratio of the polyvinyl alcohol to the tellurium nanomaterial and the cross-linking agent is: 1: (0.005-0.06): (0.1-0.5). This helps to subsequently form a composite foam material with a suitable degree of cross-linking. Optionally, the mass ratio of polyvinyl alcohol to the acid catalyst is 1: (0.1-0.5), and correspondingly, the mass ratio of the cross-linking agent to the acid catalyst is (0.1-0.5): (0.1-0.5). An appropriate amount of acid catalyst can ensure that the configured precursor solution has a suitable cross-linking speed and uniform cross-linking strength at a certain temperature. In addition, the mass ratio of polyvinyl alcohol to the foam stabilizer is 1: (0.025-0.2). An appropriate amount of foam stabilizer helps to make the resulting composite foam material have good structural stability and stable compression-rebound properties.

[0023] When preparing the precursor solution, the form of the raw materials and the specific mixing method are not limited. For example, a polyvinyl alcohol aqueous solution and a crosslinker solution can be prepared first, and then these can be mixed with the aforementioned tellurium nanomaterial, acid catalyst, and foam stabilizer. Alternatively, the tellurium nanomaterial can be added to the polyvinyl alcohol aqueous solution first, followed by the crosslinker and foam stabilizer, and finally the acid catalyst. In some embodiments of the present application, the precursor solution is prepared by mixing the aforementioned tellurium nanomaterial with the polyvinyl alcohol aqueous solution, the crosslinker solution, the acid catalyst, and the foam stabilizer at -5 to 10°C. Optionally, the weight percentage of polyvinyl alcohol in the polyvinyl alcohol aqueous solution can be 5-20% by weight, for example, 10%. In one embodiment, the weight percentage of the crosslinker in the crosslinker solution is 50% by weight. In some embodiments, the amount of tellurium nanomaterial used can be 10 to 50 mg, preferably 20 to 40 mg, for example, 35 mg. When the foam stabilizer is F-127, the amount used can be 10 to 80 mg, for example, 20 mg.

[0024] In some embodiments of the present application, in step (2), the stirring speed of the ultra-high speed stirring can be 20,000 to 40,000 rpm, for example, 22,000 rpm, 25,000 rpm, 30,000 rpm, 35,000 rpm, 38,000 rpm, etc. Among them, the ultra-high speed stirring of the precursor solution in step (1) is conducive to achieving foaming, especially conducive to the formation of rich foam of PVA. In addition, the presence of the foam stabilizer can make the obtained foam refined and uniform, while ensuring the short-term stability of the foam. At an appropriate temperature (such as 20 to 50°C mentioned in step (3), the PVA foam can undergo a cross-linking reaction with the cross-linking agent to form a Te-based composite foam material with certain mechanical strength and rich pores, and encapsulate the tellurium nanomaterial therein. Among them, the coating of the composite foam helps to further reduce the agglomeration of the tellurium nanomaterial dispersed therein, significantly improving the service life of the tellurium nanomaterial and the efficient use of its photothermal effect.

[0025] Therefore, the Te-based composite foam material obtained above has a rich porous structure, is light in weight, can float on the sea surface, and exhibits excellent water absorption. After absorbing water, it can still remain floating on the sea surface. The seawater desalination of the composite foam material can be achieved with the help of the stable photothermal effect of tellurium nanomaterials; and the composite foam material also has excellent compressibility and good elasticity, which is easy to clean and reuse.

[0026] Optionally, in step (2), the crosslinking time is 2-20 min, 5-15 min, for example, 10 min. In the present application, after obtaining the crude crosslinked composite foam material, the purpose of dialyzing it in water is to remove excess raw materials, such as crosslinking agent, acid catalyst, etc. Optionally, the dialysis can be carried out at a temperature of 4-10° C. and the dialysis time can be 48-72 h.

[0027] The preparation method of the Te-based composite foam material provided in this application uses tellurium nanomaterials as the photothermal reagent and polyvinyl alcohol-based foam as the carrier for dispersing the photothermal reagent. The resulting Te-based composite foam material is a novel product with many advantages, including good water absorption, light weight, significant photothermal effect, and good compressibility. It is expected to be applied in the field of solar thermal seawater desalination. The above preparation method is simple, easy to operate, low-cost, high-yield, and easy to achieve industrial production.

[0028] It should be noted that, although the preparation method of the composite foam material provided above in this application uses a foam system containing polyvinyl alcohol and a cross-linking agent as an example, it should be understood that other foam systems can also be used to load tellurium nanomaterials, such as a system formed by cellulose, polysaccharides or their derivatives and a cross-linking agent (such as epichlorohydrin).

[0029] On the third aspect, the embodiments of the present application also provide a Te-based composite foam material, comprising a porous foam matrix having a three-dimensional porous structure, wherein the porous foam matrix is ​​loaded with the above-mentioned tellurium nanomaterial of the embodiments of the present application, wherein the porous foam matrix has a skeleton structure formed by cross-linking polyvinyl alcohol, a cross-linking agent, and a foam stabilizer.

[0030] The above-mentioned Te-based composite foam material has a rich three-dimensional porous structure, is light in weight, can float on the sea surface, and shows excellent water absorption, and can still keep floating on the sea surface after absorbing water. Under the irradiation of sunlight, the Te nanomaterial loaded in the composite foam material shows an efficient photothermal effect, which increases the temperature of the composite foam material, causes the seawater adsorbed therein to evaporate, and can collect the fresh water that continuously evaporates from the composite foam. The composite foam material can absorb seawater to fill the free water vacancies therein due to its porous properties, thereby realizing the continuous absorption and evaporation of seawater, and can collect the fresh water that continuously evaporates from the composite foam. In addition, the above-mentioned composite foam material with a porous structure also has excellent compressibility and resilience, and it can be easily cleaned like a "sponge" and is easy to reuse.

[0031] It can be seen that the above-mentioned Te-based composite foam materials have enriched the application product forms of tellurium nanomaterials. The structural stability of tellurium nanomaterials in the composite foam system is high, and the photothermal effect can be fully exerted. With the help of the light weight and good water absorption of the porous foam matrix, seawater desalination is achieved, which expands the practical application scope of tellurium nanomaterials.

[0032] In the embodiment of the present application, the porosity of the porous foam matrix is ​​greater than or equal to 90%, for example, greater than or equal to 92%, greater than or equal to 94%, or even greater than or equal to 95%. A higher porosity is beneficial for the Te-based composite foam material to absorb seawater and sunlight, and is conducive to achieving lightweighting.

[0033] In embodiments of the present application, the Te-based composite foam material has a rough outer surface. However, the hydrogel product formed by crosslinking the precursor solution without ultra-high-speed stirring has a smooth surface. Therefore, the Te-based composite foam material provided in embodiments of the present application can have better sunlight absorption performance. In embodiments of the present application, the Te-based composite foam material has an absorptivity greater than or equal to 70% for sunlight in the full wavelength range of 250nm-2500nm, particularly high absorptivity for sunlight in the higher-energy wavelength range of 250nm-1500nm.

[0034] In the embodiment of the present application, the contact angle of the outer surface of the Te-based composite foam material with water is 0°. This indicates that the composite foam material has superhydrophilicity and a high water absorption rate. The water absorption rate of the Te-based composite foam material in 10 seconds is 1600% to 2010%. That is, the water absorption rate is 160-201%˙s -1 In some embodiments, the water absorption rate in 10 seconds is 1680% to 2010%. In addition, the composite foam material can basically reach water absorption equilibrium within 30 seconds.

[0035] In some embodiments of the present application, the tellurium nanomaterial is loaded into the skeleton structure of the porous foam matrix. Furthermore, the tellurium nanomaterial may be encapsulated by the porous foam matrix. This can further improve the dispersibility of the tellurium nanomaterial and facilitate the photothermal effect.

[0036] In embodiments of the present application, the tellurium nanomaterial may comprise 0.22% to 4.67% by mass of the Te-based composite foam. A relatively low mass fraction of tellurium nanomaterials can ensure a good photothermal effect of the composite foam. In some embodiments, the mass of the tellurium nanomaterial is 0.005 to 0.06 times the mass of the polyvinyl alcohol.

[0037] The present application also provides the use of tellurium nanomaterials prepared by the preparation method described in the first aspect of the embodiments of the present application, or the Te-based composite foam materials described in the third aspect of the embodiments of the present application in the preparation of seawater desalination materials, water treatment materials, elastic materials, photothermal materials, absorption materials, etc.

[0038] In particular, the Te-based composite foam material has many advantages, such as high stability, compressibility, significant photothermal effect, and good water absorption, making it particularly suitable for the field of solar thermal desalination. Of course, the application of this composite foam material is not limited to the above-mentioned desalination field, but can also be used in water treatment and photothermal fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The process photos of preparing Te nanomaterials by electrochemical stripping method in Comparative Example 1 and Example 1 are summarized, wherein Figure 1 Figure a (the four figures above) represents the process photos of preparing Te nanomaterials in Comparative Example 1. Figure 1 Figure b (the following 4 figures) represents the process photos of preparing Te nanomaterials in Example 1.

[0040] Figure 2 Macroscopic photographs of the post-reaction mixed solution and the post-centrifugation filtrate of the Te nanomaterials prepared by the electrochemical stripping method in Example 1 and Comparative Example 1 are summarized.

[0041] Figure 3 The transmission electron microscope (TEM) images of Te nanomaterials prepared by electrochemical stripping method in Example 1 and Comparative Example 1 are summarized, wherein: Figure 3 Figure a is a TEM image of the product of Comparative Example 1 obtained by applying a voltage of +5 V; Figure 3 Figures b and c are TEM photos of the product of Example 1 produced at -5V voltage at different magnifications.

[0042] Figure 4 The infrared spectrum of the Te nanomaterial prepared in Example 1 is provided.

[0043] Figure 5 Shows macroscopic photographs of three different preparation stages in the preparation of Te-based composite foam materials of application examples 4, 3, 2, and 1 (from left to right) of this application, wherein: Figure 5 a in the middle is the homogeneous solution stage, Figure 5 b is the foaming stage, Figure 5 The middle c is the cross-linking stage.

[0044] Figure 6 The following are cross-sectional scanning electron microscope (SEM) photos of the Te-based composite foam material in Application Example 4 of the present application and photos of its element distribution.

[0045] Figure 7 The X-ray diffraction patterns of the PVA raw materials and the products of Application Comparative Example 2, Application Comparative Example 3 and Application Examples 1-4 are summarized.

[0046] Figure 8 The water absorption properties of the composite foam materials of Application Examples 1-4 and Comparative Example 1 of the present application are summarized.

[0047] Figure 9 The solar light absorption characteristics of the composite foam materials of Application Examples 2-4 of the present application are summarized. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention in more detail. The embodiments of the present invention are not limited to the specific embodiments below. Within the scope of the principal rights, appropriate modifications may be made. Unless otherwise specified, the raw materials and other chemical reagents used in the embodiments of the present invention are commercially available products.

[0049] Example 1

[0050] A preparation method of Te nanomaterials, comprising:

[0051] A single electrolytic cell is selected as a chemical reaction container, wherein the chemical reaction container is filled with an electrolyte, wherein the electrolyte is acetonitrile containing an electrolytic ionic liquid (specifically 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt), wherein the concentration of the electrolytic ionic liquid in the acetonitrile is 0.1 mol / L; a Te crystal block is used as a working electrode (i.e., a cathode), a high-purity platinum sheet is used as a counter electrode (i.e., an anode), and no reference electrode is used. The distance between the working electrode and the counter electrode is set to 1 to 3 cm, and the above two electrodes are placed in the single electrolytic cell filled with the electrolyte;

[0052] Then, a working voltage of -5V is applied to the working electrode to react for 2 hours. During the reaction, the color of the electrolyte gradually deepens. After the reaction is completed, a mixed solution containing chemically modified tellurium nanomaterials, acetonitrile, ionic liquid, etc. is obtained; the mixed solution is vacuum filtered, and the filtered product is washed with a solvent (specifically, acetonitrile, ethanol, and water can be used for washing in sequence), and the solid powder obtained by drying is the chemically modified tellurium nanomaterial.

[0053] Example 2

[0054] A preparation of Te nanomaterial, which is different from Example 1 in that the working voltage of electrochemical stripping is -3V and the stripping time is 3h.

[0055] Example 3

[0056] A preparation method of Te nanomaterials is different from that of Example 1 in that the electrolytic ionic liquid used is specifically 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0057] Example 4

[0058] A preparation method of Te nanomaterials is different from that of Example 1 in that the concentration of 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the electrolyte is 0.5 mol / L.

[0059] Comparative Example 1

[0060] A preparation of Te nanomaterial, which is different from Example 1 in that the working voltage used for electrochemical stripping is +5V.

[0061] Comparative Example 2

[0062] A preparation of Te nanomaterials, which is different from Example 1 in that the electrolyte used is a sulfuric acid aqueous solution with a concentration of 0.5 mol / L.

[0063] Application Example 1

[0064] A method for preparing a Te-based composite foam material comprises the following steps:

[0065] 2.875 mg of the Te nanomaterial prepared in Example 1 was thoroughly mixed with a 10 wt % aqueous solution of polyvinyl alcohol (PVA) (4 g), a 50 wt % aqueous solution of glutaraldehyde (113.75 mg of glutaraldehyde), 20 μL of a commercially available concentrated hydrochloric acid solution (12 mol / L), and 20 mg of a foam stabilizer (specifically F-127) at -5 to 10° C. to obtain a precursor solution.

[0066] The precursor solution is stirred at an ultra-high speed of 35,000 revolutions per minute and placed at 30° C. to allow the precursor solution to undergo a cross-linking reaction to obtain a cross-linked composite foam crude product; the composite foam crude product is then dialyzed in deionized water to obtain a Te-based composite foam material.

[0067] Application Example 2

[0068] The difference between Application Example 2 and Application Example 1 is that when preparing the Te-based composite foam material, the amount of Te nanomaterial prepared in Example 1 is 5.75 mg. That is, the mass ratio of Te nanomaterial to PVA is 0.0144:1.

[0069] Application Example 3

[0070] The difference between Application Example 3 and Application Example 1 is that when preparing the Te-based composite foam material, the amount of Te nanomaterial prepared in Example 1 is 11.5 mg. That is, the mass ratio of Te nanomaterial to PVA is 0.02875:1.

[0071] Application Example 4

[0072] The difference between Application Example 4 and Application Example 1 is that when preparing the Te-based composite foam material, the amount of Te nanomaterial prepared in Example 1 is 23 mg. That is, the mass ratio of Te nanomaterial to PVA is 0.0575:1.

[0073] Application Example 5

[0074] The difference between Application Example 5 and Application Example 3 is that the Te nanomaterial prepared in Example 2 is used in preparing the Te-based composite foam material.

[0075] Application Example 6

[0076] The difference between Application Example 6 and Application Example 3 is that the Te nanomaterial prepared in Example 3 is used in preparing the Te-based composite foam material.

[0077] Application Example 7

[0078] The difference between Application Example 7 and Application Example 3 is that the Te nanomaterial prepared in Example 4 is used in preparing the Te-based composite foam material.

[0079] Application Example 8

[0080] The difference between Application Example 8 and Application Example 3 is that when preparing the Te-based composite foam material, the Te nanomaterial used is prepared by a hydrothermal method.

[0081] Specifically, the method includes the following steps: mixing sodium tellurite (5 mmol), deionized water (50 mL), hydrazine hydrate (5 mL), ammonia water (5 mL) and polyvinyl pyrrolidone (molecular weight 36000, 100 mg) to obtain a homogeneous mixture, and performing a hydrothermal reaction in a reactor; the hydrothermal temperature is 180° C., and the reaction time is 3 hours; then, the reactor is naturally cooled to room temperature; and then the obtained reaction material is dialyzed with deionized water and freeze-dried to obtain a solid Te nanomaterial.

[0082] Comparative Application Example 1

[0083] A PVA hydrogel and aerogel, the preparation process of which differs from that of Application Example 1 in that: a PVA aqueous solution, a glutaraldehyde aqueous solution, and concentrated hydrochloric acid are directly mixed at low temperature to obtain a precursor solution; the precursor solution is then stirred at 500 rpm and placed at 30°C for cross-linking to obtain a cross-linked hydrogel crude product; the crude hydrogel is then dialyzed in deionized water for purification and freeze-dried to obtain a PVA aerogel.

[0084] Application Comparative Example 2

[0085] A PVA foam material, the preparation process of which differs from that of Application Example 1 in that: a precursor solution obtained by directly mixing a PVA aqueous solution, a glutaraldehyde aqueous solution, and concentrated hydrochloric acid at low temperature is stirred at ultra-high speed, placed at 30°C for a cross-linking reaction, and then dialyzed in deionized water.

[0086] Application Comparative Example 3

[0087] A foam material containing PVA / foam stabilizer, the preparation process of which differs from that of Application Example 1 in that the precursor solution in step (2) does not contain Te nanomaterial. Specifically, the precursor solution of Application Example 3 is prepared by mixing a PVA aqueous solution (PVA amount: 400 mg), a glutaraldehyde aqueous solution (glutaraldehyde mass: 113.75 mg), commercially available concentrated hydrochloric acid (HCl molar amount: 0.24 mmol), and 20 mg of F-127 at -5 to 10°C.

[0088] Figure 1 The process photos of preparing Te nanomaterials by electrochemical stripping method in Comparative Example 1 and Example 1 are summarized, wherein Figure 1 Figure a (the four figures above) represents the process photos of preparing Te nanomaterials in Comparative Example 1. Figure 1 Figure b (the following 4 figures) represents the process photos of preparing Te nanomaterials in Example 1. Figure 1 As can be seen in Figure a, at +5V voltage, the Te crystal as the working electrode can obtain stripping products after 5s of reaction (flocculation products hang down on the working electrode), which shows that its stripping rate is fast; as the reaction time increases, the stripping products increase. Figure 1 As can be seen in Figure b, at a voltage of -5 V, after 5 seconds of reaction, only a small amount of Te nanomaterials are produced near the Te crystals used as the working electrode, which indicates that the stripping rate is slow. Then, after 300 seconds of reaction, the black Te nanomaterials and the electrolyte form two distinct phases, and the Te nanomaterials float on top, which indicates that the Te nanomaterials are not as good as the working electrode. Figure 1Compared with Example 1, the Te nanomaterial obtained in Example 1 has a smaller dispersion size. Similarly, as the reaction time increases, the number of stripping products increases. The above results show that the stripping rate and dispersion size of the obtained nano-Te are different for different stripping voltages. Furthermore, the nano-Te stripped by negative voltage in the present application has a slower stripping rate and smaller dispersion size, which is extremely beneficial for subsequent use.

[0089] Figure 2 The macroscopic photos of the mixed solution after reaction and the filtrate after centrifugation containing Te nanomaterials obtained by electrochemical stripping method in Example 1 and Comparative Example 1 are summarized. Figure 2 The post-reaction solutions of Example 1 and Comparative Example 1, prepared by the electrochemical stripping method, showed no sedimentation and were dark in color, indicating successful stripping of the nano-Te material. The different colors of the filtrates indicate that the positive and negative voltages stripped the samples differently, resulting in different chemical reactions during stripping.

[0090] Figure 3 The transmission electron microscope (TEM) images of Te nanomaterials prepared by electrochemical stripping method in Example 1 and Comparative Example 1 are summarized, wherein: Figure 3 Figure a is a TEM image of the product of Comparative Example 1 obtained by applying a voltage of +5 V; Figure 3 Figures b and c are TEM photos of the product of Example 1 produced at -5V voltage at different magnifications.

[0091] from Figure 3 It can be seen from a that the product of comparative example 1 made by +5V voltage has a larger size and the sample presents a porous continuous structure, that is, the product of comparative example 1 is an integrated material with a porous structure, which is consistent with Figure 1 The results show that although the comparative example 1 has a faster stripping rate under positive voltage, its product size is large, and it can be foreseen that it cannot be fully dispersed in the actual application process, and it shows a small specific surface area, thus failing to exert the physical properties of nano-Te. Figure 3 As shown in Figure b, the product of Example 1 produced by -5V voltage has smaller size and diverse morphologies, including one-dimensional nanowires, two-dimensional flocculent structures and three-dimensional nanoparticles. Figure 3 As shown in Figure c, the three-dimensional nanoparticles have a wide size distribution, even including quantum dots. This result shows that the Te nanomaterials exfoliated by negative voltage have rich morphologies, small sizes, and a wide distribution, which is very beneficial for the wide-spectrum absorption of sunlight in practical applications.

[0092] Figure 4 The infrared spectrum of the Te nanomaterial prepared in Example 1 is provided. Figure 4It can be seen that, compared with the ionic liquid used, the surface of the product Te nanomaterial prepared in Example 1 and Comparative Example 1 of the present application has abundant chemical functional groups.

[0093] In addition, in Comparative Example 2, which used a 0.5 mol / L aqueous sulfuric acid solution as the electrolyte, the Te nanomaterial produced had only one morphology, specifically Te nanorods. This is not very advantageous for using the Te nanomaterial obtained in Comparative Example 2 for manufacturing solar thermal materials, as it does not absorb sunlight well.

[0094] Figure 5 Shows macroscopic photographs of three different preparation stages in the preparation of Te-based composite foam materials of application examples 4, 3, 2, and 1 (from left to right) of this application, wherein: Figure 5 a in the middle is the homogeneous solution stage, Figure 5 b is the foaming stage, Figure 5 In the figure c is the cross-linking stage. Figure 5 Figure a is a photo of each precursor solution without high-speed stirring. Figure 5 Figure b is a photo of the foaming solution obtained after high-speed stirring of each precursor solution. Figure 5 Figure c is a photograph of each composite foam crude product after the cross-linking reaction.

[0095] from Figure 5 It can be seen that the volume of the precursor solution containing Te nanomaterials, PVA, F-127, crosslinking agent and acid catalyst increased significantly to about twice its original volume after high-speed stirring treatment. This is mainly due to the bubbles introduced by its high speed. The increase in the volume of the foaming solution means an increase in the pore structure of the system. Moreover, the higher the content of Te nanomaterials, the darker the color of the foam. After chemical crosslinking, the volume of the sample was fixed and did not shrink, which indicates that the bubbles in the sample system were retained after crosslinking, forming a porous pore structure.

[0096] Figure 6 The following is a scanning electron microscope (SEM) photograph of the cross section of the Te-based composite foam material in Example 4 of this application and its element distribution photograph. Figure 6 It can be seen that the Te nanomaterial / PVA / F-127 composite foam material of Application Example 4 has a densely packed three-dimensional porous structure, which is very beneficial for the rapid transportation of water. Figure 6 The distribution of carbon (C), oxygen (O) and tellurium (Te) elements in the composite foam material is also shown. The results show that the three elements are evenly distributed, indicating that PVA and Te nanomaterials have good dispersion, and the good dispersion of Te nanomaterials is very important for its full photothermal effect.

[0097] Figure 7The X-ray diffraction patterns of the PVA raw materials and the products of Application Comparative Example 2, Application Comparative Example 3 and Application Examples 1-4 are summarized. Figure 7 It can be known that the PVA raw material has a distinct diffraction peak, which indicates its high degree of crystallinity, which is the main diffraction characteristic of crystalline PVA. In contrast, the precursor solutions of Comparative Example 2 (without foam stabilizer) and Comparative Example 3 (containing foam stabilizer) are stirred at high speed and cross-linked to obtain products with much lower crystallinity, which can be obtained by significantly reducing the diffraction peak intensity and significantly increasing the half-peak width. The same phenomenon of reduced crystallinity can also be seen in the diffraction patterns of the products of Application Examples 1-4. In addition, a faint crystallization peak of Te (2θ is about 26.5°) can be observed in the products of Application Examples 1-4, and its weaker signal indicates that the amount of Te nanomaterial is small.

[0098] Figure 8 The water absorption (transport) characteristics of the composite foam materials of Application Examples 1-4 and Comparative Example 1 of this application are summarized. Figure 8 It can be seen that although the ordinary PVA hydrogel product (Comparative Example 1) has a certain porous structure, its water absorption rate is 0 in a very short time of 90 seconds; that is, in such a short time, ordinary PVA hydrogel cannot absorb water quickly at all. However, the products of Application Examples 1-4 of the present application all show extremely fast absorption characteristics. For example, within 10 seconds, the water absorption rates of the products of Application Examples 1-4 can reach approximately 1680%, 1815%, 1824% and 2010%, respectively, and after no more than 30 seconds, the water absorption rates of all application example products reach equilibrium. Wherein, water absorption rate = (mass after water absorption - mass before water absorption) / sample mass before water absorption. The above results show that the composite foam material prepared in the examples of the present application has excellent water transport properties, which is very beneficial for absorbing seawater and continuously supplying seawater.

[0099] Figure 9 The solar absorption characteristics of the composite foam materials of application examples 2-4 of this application are summarized. Figure 9It can be known that the final products of application examples 2-4 show full-band sunlight absorption behavior under the concentration dependence of Te nanomaterials. Among them, when the content of Te nanomaterials is low (such as application example 2), the absorptivity of the sample is about 70% in the wavelength range of about 250-1300nm with higher energy, and the absorptivity of the sample is about 67% in the wavelength range of about 1500-2000nm with weaker energy. The absorptivity of the sample is about 85% in the wavelength range of about 2000-2500nm. When the content of Te nanomaterials in the composite foam material is high (such as application example 4), the light absorptivity of the sample in the above three wavelength ranges increases to more than 95%, more than 84% and more than 90% respectively. In general, the composite foam material product implemented in this application has a high absorptivity to sunlight, which is very beneficial for efficient light-heat conversion behavior and is conducive to achieving seawater desalination.

[0100] In addition, Table 1 below also summarizes the relevant test results of the Te-based composite foam materials prepared in the above-mentioned application examples and the products prepared in the application comparative examples.

[0101] Table 1

[0102]

[0103] The test conditions for the mechanical recovery data in Table 1 are as follows: Equipment: Instron 9566 tensile testing machine, pressure sensor: 500 N; test fixture: compression type fixture; test conditions: room temperature; compression speed: 1 mm / min; detection mode: compression recovery mode.

[0104] The water absorption rate within 10 seconds in Table 1 was measured as follows: Samples (cylindrical, approximately 5-6 cm high) from each Example or Comparative Example were freeze-dried to a completely dry state, and the sample mass was recorded. The bottom of each sample was then immersed in seawater (to a depth of 0.5-1 cm) for 10 seconds. The mass of each sample after water absorption was recorded after 10 seconds. The difference between the sample mass after water absorption and the mass before water absorption was calculated as the ratio of the sample mass before water absorption to the sample mass before water absorption, which was used as the water absorption rate.

[0105] The seawater evaporation rate test method in Table 1 is as follows: Samples from each example or comparative example are placed in a container filled with seawater and the initial weight of the entire container is measured. The container is then exposed to sunlight for a period of time. The ratio of the total mass loss (i.e., the mass of evaporated seawater) to the surface area of ​​the sample exposed to sunlight and the exposure duration is used as the seawater evaporation rate for each sample.

[0106] The energy efficiency of seawater evaporation in Table 1 was tested as follows: each sample of the embodiment or comparative example was embedded in a black foam body, and the whole was placed in a container filled with seawater. One times the amount of sunlight was applied from above, and the ratio of the energy required to evaporate the seawater of each sample to the energy provided by one times the amount of sunlight was used as the energy efficiency.

[0107] From Table 1, we can see that

[0108] The above disclosure is only an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present application. These improvements and modifications are also considered to be within the scope of protection of the embodiments of the present application.

Claims

1. A method for preparing tellurium nanomaterials, characterized in that: The following steps are involved: A tellurium crystal is used as a cathode and an inert electrode is used as an anode. The cathode and anode are placed in an electrolytic cell filled with an electrolyte, and an operating voltage of -2V to -8V is applied to the cathode to perform an electrochemical stripping reaction, thereby obtaining a mixed solution containing tellurium nanomaterials in the electrolytic cell. The electrolyte is an acetonitrile solution containing an electrolytic ionic liquid. The tellurium nanomaterials include various morphologies, including tellurium nanowires, tellurium nanoparticles, and flocculent tellurium nanomaterials. The surface of the tellurium nanomaterials is modified with an electrolysis product of the electrolytic ionic liquid. The mixed solution is subjected to solid-liquid separation, and the obtained solid matter is washed and dried in sequence, and the obtained solid matter is the tellurium nanomaterial.

2. The method for preparing tellurium nanomaterials according to claim 1, wherein: The electrolytic ionic liquid includes one or more of 1-aminopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium (methylsulfonyl trifluoro)imide, N-butylpyridine bis(trifluoromethanesulfonyl)imide, and 1-butyl-1-methylpyrrole trifluoromethanesulfonate.

3. The method for preparing tellurium nanomaterials according to claim 2, wherein: The concentration of the electrolytic ionic liquid in the electrolyte is 0.05-1 mol / L.

4. The method for preparing tellurium nanomaterials according to claim 1, wherein: The electrochemical stripping reaction time is 5 minutes to 12 hours.

5. A tellurium nanomaterial, characterized in that: The tellurium nanomaterial is prepared by the preparation method of any one of claims 1 to 4.

6. A method for preparing a Te-based composite foam material, characterized in that: The following steps are involved: (1) Mixing the tellurium nanomaterial according to claim 5 with polyvinyl alcohol, a crosslinking agent, a foam stabilizer, an acid catalyst, and water at -5 to 10° C. to obtain a precursor solution; (2) The precursor solution is stirred at an ultra-high speed at a speed greater than or equal to 10,000 rpm, and is placed at 20-50° C. to undergo cross-linking to obtain a cross-linked composite foam material crude product; the composite foam material crude product is then dialyzed in water to obtain a Te-based composite foam material.

7. The preparation method according to claim 6, wherein The mass ratio of the polyvinyl alcohol to the tellurium nanomaterial is 1: (0.005-0.06); the mass ratio of the polyvinyl alcohol to the foam stabilizer is 1: (0.025-0.2); the mass ratio of the polyvinyl alcohol to the cross-linking agent is 1: (0.1-0.5); and the mass ratio of the polyvinyl alcohol to the acid catalyst is 1: (0.1-0.5).

8. The preparation method according to claim 6, wherein The foam stabilizer includes one or more of alkyl polyglycosides, cationic surfactants, anionic surfactants and nonionic surfactants; the crosslinking agent is selected from one or more of dialdehydes, paraformaldehyde, urea-formaldehyde resin, melamine-formaldehyde resin, boron compounds and maleic anhydride; the acid catalyst includes one or more of hydrochloric acid, sulfuric acid and acetic acid.

9. A Te-based composite foam material, characterized in that It includes a porous foam matrix with a three-dimensional porous structure and a tellurium nanomaterial loaded in the porous foam matrix, wherein the porous foam matrix has a skeleton structure formed by cross-linking polyvinyl alcohol, a cross-linking agent, and a foam stabilizer; the Te-based composite foam material is prepared by the preparation method according to any one of claims 6 to 8.

10. The Te-based composite foam material according to claim 9, wherein The outer surface of the Te-based composite foam material is rough.

11. The Te-based composite foam material according to claim 9, wherein The water absorption rate of the Te-based composite foam material in 10 seconds is 1600% to 2010%.

12. Use of the tellurium nanomaterial prepared by the method for preparing the tellurium nanomaterial according to any one of claims 1 to 4 and the Te-based composite foam material according to any one of claims 9 to 11 in preparing seawater desalination materials, water treatment materials, elastic materials, and photothermal materials.

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